EP4253602A1 - Electrochemical oxidation of cycloalkenes and cycloalkanes to alpha, omega-dicarboxylic acids or ketocarboxylic acids and cycloalkanone compounds - Google Patents

Abstract

The invention relates to a process for the preparation of unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids and unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes and unsubstituted or at least monosubstituted, saturated ones cycloaliphatic hydrocarbons in the presence of an inorganic or organic nitrate salt in an electrolysis cell in a reaction medium in the presence of oxygen.

Description

The invention relates to a process for the preparation of unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids and unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes and unsubstituted or at least monosubstituted, saturated ones cycloaliphatic hydrocarbons in the presence of an inorganic or organic nitrate salt in an electrolysis cell in a reaction medium in the presence of oxygen.

α,ω-dicarboxylic acids, ketocarboxylic acids and cycloalkanone compounds represent important starting materials for organic synthetic chemistry as well as monomer building blocks for polymer synthesis and are therefore highly relevant for industrial applications. The conventional access to these substrates is essentially from cycloalkanes and cycloalkenes via transition metal-catalyzed reactions and using chemical oxidants.

A method for the electrochemical oxidation of cycloalkanes to the corresponding ketones has not yet been described. Only a few examples are known of the electrochemical, oxidative double bond cleavage of cyclooctene and cyclododecene to form dicarboxylic acids or their methyl esters ( U. Baumer, Electrochimica Acta 2003, 48, 489-495 ; U.-St. Bäumer, HJ Schäfer, J. Appl. Electrochem. 2005, 35, 1283-1292 ; DD Davis, DL Sullivan, Process for the Preparation of Dodecanedionic Acid, 1991 and US 5026461 A ). The synthesis of dicarboxylic acids by oxidative double bond cleavage is based on pure cycloalkenes.

In these prior art processes, the synthesis often leads to the corresponding carboxylic acid esters, so that a further hydrolysis step is necessary to generate the free carboxylic acids, which requires additional time and resources.

The use of expensive transition metals, as electrocatalysts or as electrode materials, as well as the use of chemical oxidizing agents lead to the accumulation of reagent waste due to the increased use of materials, some of which have to be disposed of or regenerated at great expense. Furthermore, the processes require a high overall use of materials due to the use of complex electrolyte systems and additional oxidizing agents, which has an overall negative effect on the cost balance and the economic efficiency of the processes.

It is an object of the invention to provide a sustainable and resource-saving process which enables the production of α,ω-dicarboxylic acids and cycloalkanones.

This task was solved by the subject matter of the patent claims and the description.

• (a-1) Bereitstellung wenigstens eines unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens;
• (a-2) Bereitstellung wenigstens eines unsubstituierten oder wenigstens einfach substituierten, gesättigten cycloaliphatischen Kohlenwasserstoffs;
• (b) Bereitstellung wenigstens eines anorganischen oder organischen Nitratsalzes;
• (c) elektrochemische Oxidation des in Schritt (a-1) bereitgestellten unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens und des in Schritt (a-2) bereitgestellten unsubstituierten oder wenigstens einfach substituierten, gesättigten cycloaliphatischen Kohlenwasserstoffs in Gegenwart des in Schritt (b) bereit gestellten anorganischen oder organischen Nitratsalzes in einer Elektrolysezelle in einem Reaktionsmedium in Gegenwart von Sauerstoff.

The present invention relates to a process for producing unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids and unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation, comprising the process steps:

• (a-1) providing at least one unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene;
• (a-2) providing at least one unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon;
• (b) providing at least one inorganic or organic nitrate salt;
• (c) electrochemical oxidation of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene provided in step (a-1) and the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon provided in step (a-2) in the presence of the one provided in step (a-2). b) provided inorganic or organic nitrate salt in an electrolysis cell in a reaction medium in the presence of oxygen.

Surprisingly, it was found that in the process according to the invention, cyclic alkenes are formed in the presence of cyclic alkanes thereof Ring size, let it be electrochemically oxidized to α,ω-dicarboxylic acids or ketocarboxylic acids.

It is therefore possible with the process according to the invention to convert technically obtained cycloalkenes, which often contain a certain proportion of cycloaliphatic hydrocarbons, into α,ω-dicarboxylic acids, with cyclic ketones being obtained as further products, which can also be used in technical applications.

The method according to the invention thus enables the simplification of industrially relevant processes and further leads to possible process optimization from a sustainable perspective.

The present invention enables synthetically relevant oxo-functionalization of basic chemicals in a resource-saving manner, largely eliminating the use of environmentally harmful transition metals and oxidizing agents. The selective conversion to the desired products and the effective use of conductive salt and mediator in a dual function significantly reduce the amount of costly reagent waste. The present invention allows electrochemical synthesis access to aliphatic α,ω-carboxylic acids, ketocarboxylic acids and cycloalkanones via an effective, convergent electrolysis in which both electrode reactions provide synthetic utility.

The process according to the invention is characterized in particular by high selectivity, small amounts of auxiliary chemicals used, the use of electric current as an oxidizing agent and, associated with this, by a reduced amount of waste products.

It was also surprisingly found that the method according to the invention can be carried out under ambient pressure and ambient temperature, which also has an advantageous effect on energy efficiency and thus also environmental compatibility.

Unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes that are monocyclic or bicyclic can be used in the process according to the invention. Preference is given to unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated monocyclic Cycloalkenes are used, with unsubstituted or at least monosubstituted, monounsaturated monocyclic cycloalkenes being particularly preferred. The location of the unsaturated bonds can be endocyclic or exocyclic, with endocyclic unsaturated bonds being preferred.

The unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated monocyclic cycloalkenes used in the process according to the invention can preferably have 5 to 12 C atoms, particularly preferably 6 to 12 C atoms, very particularly preferably 8 to 12 C atoms in the ring system. These cycloalkenes can be monounsaturated or polyunsaturated, with monounsaturated cycloalkenes being preferred. These cycloalkenes can each be unsubstituted or mono- or poly-substituted. If they are substituted once or multiple times, they are preferably substituted with 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl. The phenyl or benzyl substituents themselves can each be unsubstituted or mono- or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ .

The unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated bicyclic cycloalkenes used in the process according to the invention can preferably have 7 to 18 C atoms, particularly preferably 7 to 12 C atoms, very particularly preferably 7 to 10 C atoms in the ring system. These cycloalkenes can be monounsaturated or polyunsaturated, with monounsaturated cycloalkenes being preferred. These cycloalkenes can each be unsubstituted or mono- or poly-substituted. If they are substituted once or multiple times, they are preferably substituted with 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl. The phenyl or benzyl substituents themselves can each be unsubstituted or mono- or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ .

If the mono- or bicyclic cycloalkenes used according to the invention or their substituents are alkyl radicals with more than one carbon atom in the side chain have, undesirable side reactions occur at these substituents when carrying out the process according to the invention.

The monocyclic cycloalkene can very particularly preferably be selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene and 1-phenylcyclohex-1-ene. Particularly preferred bicyclic cycloalkenes can be selected from the group consisting of bicylo[2.2.1]hept-2-ene, α-pinene and carene.

Unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbons which are monocyclic or bicyclic, preferably bicyclic, can be used in the process according to the invention. Monocyclic cycloaliphatic hydrocarbons are particularly preferably used in the process according to the invention.

The monocyclic or polycyclic, in particular monocyclic or bicyclic, saturated cycloaliphatic hydrocarbons used in the process according to the invention can preferably have 5 to 18 C atoms in the ring system. These cycloaliphatic hydrocarbons can each be unsubstituted or mono- or poly-substituted. If they are substituted once or multiple times, they are preferably substituted with 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl. The phenyl or benzyl substituents themselves can each be unsubstituted or mono- or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ . If the cycloaliphatic hydrocarbons used according to the invention or their substituents have alkyl radicals with more than one carbon atom in the side chain, undesirable side reactions occur at these substituents when carrying out the process according to the invention.

Particularly preferred in the process according to the invention are monocyclic saturated hydrocarbons with 6 to 12 carbon atoms in the ring, preferably with 8 to 12 carbon atoms in the ring, which are unsubstituted or substituted once or multiple times with 1 as unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbons , 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl. Very particular preference is given to using monocyclic saturated hydrocarbons with 8 to 12 carbon atoms in the ring in the process according to the invention, which are unsubstituted or mono- or di- or tri-substituted with a methyl group.

Very particularly preferably, the saturated monocyclic hydrocarbon is unsubstituted and is selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane, even more preferably selected from the group consisting of cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane, the hydrocarbon cyclododecane is most preferred.

The cycloalkene is particularly preferably selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, 1-phenylcyclohex-1-ene, bicylo[2.2.1]hept-2-ene, α-pinene and carene and the saturated cycloaliphatic hydrocarbon selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane.

Very particularly preferred is the cycloalkene cyclododecene and the saturated cycloaliphatic hydrocarbon cyclododecane.

The provision of at least one unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene according to step (a-1) and the provision of at least one unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon according to step (a-2) can preferably be carried out in the process according to the invention Combination, particularly preferably as a mixture. For example, preliminary products from large-scale industrial processes that contain these two components can be used directly in the process according to the invention.

The quantitative ratio of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon in the process according to the invention can vary over a wide range. The molar proportion of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene is preferably 40 to 95 mol%, preferably 45 to 55 mol%, particularly preferably 47 to 53 mol%, in each case based on the total amount of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon used.

Also preferably, the molar proportion of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene is >60 mol%, preferably >65 mol%, particularly preferably >70 mol%, in each case based on the total amount used unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene and unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbon.

The cycloalkene used is very particularly preferably cyclododecene in an amount of 90 to 95 mol% and the saturated cycloaliphatic hydrocarbon cyclododecane is used in an amount of 5 to 10 mol%, based on the total amount of cyclodecene and cyclodecane.

mit R¹ und R², unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt, und R³ ausgewählt aus der Gruppe bestehend aus H und C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere aus der Gruppe bestehend aus H und C₁- bis C₈-Alkyl, geradkettig oder verzweigt,According to step (b) of the process according to the invention, at least one inorganic or organic nitrate salt is provided. This nitrate salt acts both as a conductive salt and as a mediator in the electrochemical oxidation process according to the invention. An inorganic or organic nitrate of the general formula is preferred

[Cation ⁺ ][NO ₃ ^- ]

for use, whereby the [cation ⁺ ] is selected from the group consisting of Na ⁺ , K ⁺ , ammonium ions with the general structure [R ¹ R ² R ³ R ⁴ N ⁺ ] with R ¹ , R ² , R ³ , R ⁴ , independently of one another, each selected from the group consisting of C ₁ - to C ₁₆ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, imidazolium cations with the general structure (I)

with R ¹ and R ² , independently of one another, each selected from the group consisting of C ₁ - to C ₁₈ alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, and R ³ selected from Group consisting of H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -alkyl, straight-chain or branched,

mit R¹ ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt und R², R³ und R⁴, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus H und C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere aus der Gruppe bestehend aus H und C₁- bis C₈-Alkyl, geradkettig oder verzweigt, undPyridinium cations with the general structure (II)

with R ¹ selected from the group consisting of C ₁ - to C ₁₈ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched and R ² , R ³ and R ⁴ , independently of one another, each selected from the group consisting from H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -alkyl, straight-chain or branched, and

Phosphonium ions with the general structure [R ^1a R ^2a R ^3a R ^4a P ⁺ ] with R ^1a , R ^2a , R ^3a , R ^4a , independently of one another, each selected from the group consisting of C ₁ - to C ₁₆ alkyl, in particular C ₁ - to C ₈ alkyl, straight chain or branched.

If an organic nitrate based on the imidazolium cations is used in the process according to the invention, preference is given to those cations of the general formula (I) in which R ¹ and R ² , independently of one another, are each selected from the group consisting of C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched and R ³ is hydrogen. Particular preference is given to imidazolium cations of the general formula (I) in which R ¹ is methyl and R ² is ethyl or R ¹ is methyl and R ² is Methyl and R ¹ is methyl and R ² is butyl, and R ³ is each hydrogen.

If a nitrate based on the pyridinium cations is used in the process according to the invention, preference is given to those cations of the general formula (II) in which R ¹ is C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - until C ₈ alkyl, straight chain or branched. Particular preference is given to pyridinium cations of the general formula (II) in which R ¹ is C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, and the radicals R ² , R ³ and R ⁴ , independently of one another, are each selected from the group consisting of C ₁ - to C ₈ alkyl, straight-chain or branched, where a single substitution in the 2-, 3- or 4-position, a double substitution in 2,4-, 2,5- or 2,6-position or a triple substitution in 2,4,6-position is preferred.

In principle, two or more of the above-mentioned nitrate salts can also be used in the process according to the invention. A nitrate salt according to the invention is preferably used, in particular an organic ammonium nitrate salt of the composition [R ¹ R ² R ³ R ⁴ N ⁺ ][NO ₃ ^- ] or an organic phosphonium salt of the composition [R ^1a R ^2a R ^3a R ^4a P ⁺ ][NO ₃ ^- ], with an organic ammonium nitrate salt of the composition [R ¹ R ² R ³ R ⁴ N ⁺ ][NO ₃ ^- ] being particularly preferred.

The organic ammonium nitrate salt tetra- n -butyl ammonium nitrate or methyltri- n -octylammonium nitrate is very particularly preferred. The organic phosphonium nitrate salt is most preferably tetra- n -butylphosphonium nitrate or methyltri- n -octylphosphonium nitrate. The organic imidazolium nitrate salt is preferably 1-butyl-3-methylimidazolium nitrate.

Tetra- n -butyl ammonium nitrate or methyltri- n -octylammonium nitrate is most preferably used as the organic nitrate salt in the process according to the invention.

The order in which the components used in the method according to the invention are provided can vary, as can the order individual components are brought into contact with each other or with the respective reaction medium.

In one embodiment of the process according to the invention, the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon are introduced and brought together with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed with it, and then the inorganic or organic nitrate salt is added.

In a further embodiment of the process according to the invention, the inorganic or organic nitrate salt is introduced and brought into contact with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed with it, and then the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbons, preferably in combination, are added.

It is also possible to initially introduce the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon and the inorganic or organic nitrate salt and then bring them together with the reaction medium, preferably at least partially in the reaction medium to completely dissolve or mix with it. Furthermore, it is also possible in the process according to the invention for the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon and the inorganic or organic nitrate salt to be added to the reaction medium simultaneously or in time succession to one another are, preferably at least partially or completely dissolved in the reaction medium or mixed with it.

The reaction medium used in the process according to the invention is liquid under the conditions under which the process is carried out and is suitable for partially or completely dissolving the components used, ie in particular the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon and the inorganic or organic nitrate salt. If at least one of these components is used in liquid form, the reaction medium is preferably easily miscible with this component or these components.

A polar aprotic reaction medium is preferably used in the process according to the invention for electrochemical oxidation. This can be used in anhydrous form, in dried form or in combination with water.

If an inorganic nitrate salt, in particular potassium nitrate or sodium nitrate, is used in the process according to the invention, the reaction medium advantageously contains water, with aprotic reaction medium in combination with water being preferred. The water content in the reaction medium can vary. The water content is preferably up to 20% by volume, particularly preferably up to 15% by volume, very particularly preferably up to 10% by volume, even more preferably up to 5% by volume, in each case on the total amount of reaction medium.

The polar aprotic reaction medium is preferably selected from the group consisting of aliphatic nitriles, aliphatic ketones, cycloaliphatic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, and dimethyl sulfoxide, esters and ethers or a combination of at least two of these components.

The reaction medium is particularly preferably selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, acetone, dimethyl carbonate, methyl ethyl ketone, 3-pentanone, cyclohexanone, nitromethane, nitropropane, tert-butyl methyl ether, dimethyl sulfoxide, gamma-butyrolactone and epsilon-caprolactone or a combination from at least two of these components.

Very particularly preferably, the reaction medium is selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, dimethyl carbonate and acetone or a combination of at least two of these components.

The reaction medium is very particularly preferably acetonitrile, isobutyronitrile or adiponitrile in dried or anhydrous form.

The reaction medium is also very particularly preferred: acetonitrile, isobutyronitrile or adiponitrile, optionally in combination with water.

If one or more of the above-mentioned components is used in the reaction medium in combination with water, the water content is preferably up to 20% by volume, particularly preferably up to 15% by volume, very particularly preferably up to 10% by volume. %, even more preferably up to 5% by volume, based on the total amount of reaction medium.

To carry out the process according to the invention, it may be advantageous to add further solubilizing components to the reaction medium. Suitable advantageous components can be determined through simple preliminary tests on solution behavior.

Suitable solubilizing components include, for example, primary alcohols, secondary alcohols, monoketones or dialkyl carbonates or mixtures of at least two of these components, possibly in combination with water. Aliphatic C _1-6 alcohols can preferably be used in the process according to the invention, with particularly preferred solubilizing components being selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol or mixtures of at least two of these components , if necessary in combination with water.

The use of dimethyl carbonate as a reaction medium can be particularly advantageous, if necessary in combination with at least one C _1-6 alcohol, in particular selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol, if necessary in combination with be water.

If one or more of these solubilizing components is used in combination with water, the water content is preferably up to 20% by volume, particularly preferably up to 15% by volume, very particularly preferably up to 10% by volume more preferably up to 5% by volume, based on the total amount of solubilizing component and water.

The solubilizing components can preferably be added in amounts of <50% by volume, particularly preferably <30% by volume and very particularly preferably <10% by volume, in each case based on the total amount of reaction medium.

The inorganic or organic nitrate salt is preferably used in the process according to the invention in an amount of 0.1 to 2.0, preferably 0.2 to 1.0, particularly preferably 0.3 to 0.8 and very particularly preferably 0.4 to 0 .8 equivalents, based on the amount of unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene used and in an amount of 0.8 to 10.0, preferably 2.5 to 10.0, particularly preferably 3.0 to 10 .0 and very particularly preferably 5.0 to 10.0 equivalents, based on the amount of unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon used.

According to the invention, the electrochemical oxidation of the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon takes place in the presence of the inorganic or organic nitrate salt in an electrolysis cell in a reaction medium in the presence of oxygen.

For this purpose, a gas atmosphere containing oxygen is advantageously provided in spatial connection with the reaction medium.

The proportion of oxygen in the gas atmosphere can vary. The proportion of oxygen in the gas atmosphere is preferably 10 to 100% by volume, particularly preferably 15 to 30% by volume, particularly preferably 15 to 25% by volume, very particularly preferably 18 to 22% by volume.

In one embodiment, the proportion of oxygen in the gas atmosphere can be 10 to 100% by volume, particularly preferably 15 to 100% by volume, particularly preferably 20 to 100% by volume.

The gas atmosphere is particularly preferably air.

Advantageously, a gas exchange is forced between the gas atmosphere and the reaction medium, preferably by introducing gas atmosphere into the reaction medium or by stirring the liquid phase in the presence of the gas atmosphere.

The gas exchange between the gas atmosphere and the reaction medium, in particular stirring, for example via the geometry of the stirrer or the stirring speed, can be used to control the electrochemical oxidation.

The amount of oxygen dissolved in the reaction medium is preferably at least 1 mmol/L reaction medium, particularly preferably at least 5 mmol/L reaction medium.

The amount of oxygen dissolved in the reaction medium is also preferably at least 10 mmol/L reaction medium.

The process according to the invention for the preparation of unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids and unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkenes and unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbons in the presence of an inorganic or organic nitrate salt in a reaction medium in the presence of oxygen can be carried out in both a divided and an undivided electrolysis cell, with implementation in an undivided electrolysis cell being preferred.

The undivided electrolysis cell which is preferably used according to the invention has at least two electrodes. Anodes and cathodes of common materials can be used here, for example glassy carbon, boron-doped diamond (BDD) or graphite. The use of glassy carbon electrodes is preferred.

The undivided electrolysis cell preferably has at least one glassy carbon anode or at least one glassy carbon cathode. Both the anode and the cathode are preferably glassy carbon electrodes.

The distance between the electrodes can vary over a certain range. The distance is preferably 0.1 mm to 2.0 cm, particularly preferably 0.1 mm to 1.0 cm, particularly preferably 0.1 mm to 0.5 cm.

Furthermore, the process according to the invention can be carried out batchwise or continuously, preferably in an undivided flow-through electrolysis cell.

The method according to the invention is preferably carried out with a charge quantity of at least 190 C (2 F) to 970 C (10 F), preferably 290 C (3 F) to 870 C (9 F), particularly preferably 330 C (3.5 F) to 820 C (8.5 F), very particularly preferably 380 C (4 F) to 775 C (8 F), most preferably 380 C (4 F) to 580 C (6 F), each for 1 mmol of used unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene and unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbon.

The electrochemical oxidation in the process according to the invention preferably takes place at constant current intensity.

The current density at which the method according to the invention is carried out is preferably at least 5 mA/cm ² or at least 10 mA/cm ² or at least 15 mA/cm ² or at least 20 mA/cm ² or 20 mA/cm ² to 50 mA/ cm ² , whereby the area refers to the geometric area of the electrodes.

A significant advantage of the method according to the invention is that electric current is used as the oxidizing agent, which is a particularly environmentally friendly agent when it comes from renewable sources, i.e. in particular from biomass, solar thermal energy, geothermal energy, hydropower, wind power or photovoltaics.

The process according to the invention can be carried out over a wide temperature range, for example at a temperature in the range from 0 to 60 °C, preferably from 5 to 50 °C, particularly preferably 10 to 40 °C, very particularly preferably 15 to 30 °C.

The process according to the invention can be carried out at increased or reduced pressure. If the process according to the invention is carried out at elevated pressure, a pressure of up to 16 bar is preferred, particularly preferably up to 6 bar.

The process according to the invention can also preferably be carried out under atmospheric pressure.

The products produced by the process according to the invention can be isolated or purified by conventional processes known to those skilled in the art, in particular by extraction, crystallization, centrifugation, precipitation, distillation, evaporation or chromatography.

The process according to the invention is preferably carried out without the addition of catalysts, in particular without the addition of transition metal catalysts.

The process according to the invention is also preferably carried out in such a way that no other oxidizing agents are added other than oxygen or atmospheric oxygen.

• Ausführungsform 1: Verfahren zur Herstellung von unsubstituierten oder wenigstens einfach substituierten α,ω-Dicarbonsäuren oder Ketocarbonsäuren und unsubstituierten oder wenigstens einfach substituierten Cycloalkanonen durch elektrochemische Oxidation umfassend die Verfahrensschritte:
  • (a-1) Bereitstellung wenigstens eines unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens;
  • (a-2) Bereitstellung wenigstens eines unsubstituierten oder wenigstens einfach substituierten, gesättigten cycloaliphatischen Kohlenwasserstoffs;
  • (b) Bereitstellung wenigstens eines anorganischen oder organischen Nitratsalzes;
  • (c) Elektrochemische Oxidation des in Schritt (a-1) bereitgestellten unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens und des in Schritt (a-2) bereitgestellten unsubstituierten oder wenigstens einfach substituierten, gesättigten cycloaliphatischen Kohlenwasserstoffs in Gegenwart des in Schritt (b) bereit gestellten anorganischen oder organischen Nitratsalzes in einer Elektrolysezelle in einem Reaktionsmedium in Gegenwart von Sauerstoff.
• Ausführungsform 2: Verfahren nach Ausführungsform 1, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte Cycloalken monocyclisch oder bicyclisch, vorzugsweise monocyclisch ist.
• Ausführungsform 3: Verfahren nach Ausführungsform 1 oder 2, wobei das unsubstituierte oder wenigstens einfach substituierte Cycloalken einfach ungesättigt ist, vorzugsweise einfach ungesättigt und monocyclisch ist.
• Ausführungsform 4: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte monocyclische Cycloalken 5 bis 12 C Atome, besonders bevorzugt 6 bis 12 C Atome, ganz besonders bevorzugt 8 bis 12 C Atome im Ringsystem aufweist und unsubstituiert oder einfach oder mehrfach, vorzugsweise mit 1, 2, 3, 4 oder 5 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus Methyl, Phenyl oder Benzyl substituiert ist, wobei die Phenyl- bzw. Benzyl-substituenten selbst jeweils unsubstituiert oder einfach oder mehrfach substituiert sind, mit 1, 2 oder 3 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus F, Cl, Br, und NO₂.
• Ausführungsform 5: Verfahren nach einer der vorhergehenden Ausführungsformen 2 bis 4, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte bicyclische Cycloalken 7 bis 18 C Atome, besonders bevorzugt 7 bis 12 C Atome, ganz besonders bevorzugt 7 bis 10 C Atome im Ringsystem aufweist und unsubstituiert oder einfach oder mehrfach, vorzugsweise mit 1, 2, 3, 4 oder 5 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus Methyl, Phenyl oder Benzyl substituiert sind, wobei die Phenyl- bzw. Benzyl-substituenten selbst jeweils unsubstituiert oder einfach oder mehrfach substituiert sind, mit 1, 2 oder 3 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus F, Cl, Br, und NO₂.
• Ausführungsform 6: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das Cycloalken ausgewählt ist aus der Gruppe bestehend aus Cyclohexen, Cyclohepten, Cycloocten, Cyclononen, Cyclodecen, Cycloundecen, Cyclododecen, 1-Phenylcyclohex-1-en, Bicylo[2.2.1]hept-2-en, α-Pinen und Caren.
• Ausführungsform 7: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der unsubstituierte oder wenigstens einfach substituierte, gesättigte cycloaliphatische Kohlenwasserstoff monocyclisch oder bicyclisch ist, bevorzugt monocyclisch ist.
• Ausführungsform 8: Verfahren nach Ausführungsform 7, wobei der monocyclische oder bicyclische, gesättigte cycloaliphatische Kohlenwasserstoff 5 bis 18 C Atome im Ringsystem aufweist und unsubstituiert oder einfach oder mehrfach substituiert ist mit 1, 2, 3, 4 oder 5 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus Methyl, Phenyl oder Benzyl, wobei Phenyl oder Benzyl jeweils unsubstituiert oder einfach oder mehrfach substituiert sein können, mit 1, 2 oder 3 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus F, Cl, Br, und NO₂
• Ausführungsform 9: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der unsubstituierte oder wenigstens einfach substituierte, gesättigte cycloaliphatische Kohlenwasserstoff ein monocyclischer gesättigter Kohlenwasserstoff mit 6 bis 12 Kohlenstoffatomen im Ring, vorzugsweise mit 8 bis 12 Kohlenstoffatomen im Ring, ist, wobei dieser cycloaliphatische Kohlenwasserstoff unsubstituiert oder einfach oder mehrfach substituiert ist mit 1, 2, 3, 4 oder 5 Substituenten, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus Methyl, Phenyl oder Benzyl, besonders bevorzugt ein monocyclischer gesättigter Kohlenwasserstoff mit 8 bis 12 Kohlenstoffatomen im Ring, wobei dieser cycloaliphatische Kohlenwasserstoff unsubstituiert oder einfach oder zweifach oder dreifach substituiert sind mit Methyl. Ausführungsform 10: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der gesättigte cycloaliphatische Kohlenwasserstoff ausgewählt ist aus der Gruppe bestehend aus Cyclohexan, Cycloheptan, Cyclooctan, Cyclononan, Cyclodecan, Cycloundecan und Cyclododecan, vorzugsweise ausgewählt aus der Gruppe bestehend aus Cyclooctan, Cyclononan, Cyclodecan, Cycloundecan und Cyclododecan, besonders bevorzugt Cyclododecan ist.
• Ausführungsform 11: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das Cycloalken ausgewählt ist aus der Gruppe bestehend aus Cyclohexen, Cyclohepten, Cycloocten, Cyclononen, Cyclodecen, Cycloundecen, Cyclododecen, 1-Phenylcyclohex-1-en, Bicylo[2.2.1]hept-2-en, α-Pinen und Caren und wobei der gesättigte cycloaliphatische Kohlenwasserstoff ausgewählt ist aus der Gruppe bestehend aus Cyclohexan, Cycloheptan, Cyclooctan, Cyclononan, Cyclodecan, Cycloundecan und Cyclododecan.
• Ausführungsform 12: Verfahren nach Ausführungsform 11, wobei das Cycloalken Cyclododecen ist und wobei der gesättigte cycloaliphatische Kohlenwasserstoff Cyclododecan ist.
• Ausführungsform 13: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Bereitstellung wenigstens eines unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens gemäß Schritt (a-1) und die Bereitstellung wenigstens eines unsubstituierten oder wenigstens einfach substituierten, gesättigten cycloaliphatischen Kohlenwasserstoffs gemäß Schritt (a-2) in Kombination, vorzugsweise als Gemisch, erfolgt.
• Ausführungsform 14: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der molare Anteil des unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens 40 bis 95 Mol.-%, vorzugsweise 45 bis 55 Mol.-%, besonders bevorzugt 47 bis 53 Mol.-% beträgt, jeweils bezogen auf die gesamte Menge an eingesetztem unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigte Cycloalken und unsubstituiertem oder wenigstens einfach substituiertem, gesättigtem cycloaliphatischen Kohlenwasserstoff.
• Ausführungsform 15: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der molare Anteil des unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalkens > 60 Mol.-%, vorzugsweise > 65 Mol.-%, besonders bevorzugt > 70 Mol.-% beträgt, jeweils bezogen auf die gesamte Menge an eingesetztem unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigte Cycloalken und unsubstituiertem oder wenigstens einfach substituiertem, gesättigtem cycloaliphatischen Kohlenwasserstoff. Ausführungsform 16: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei als anorganisches oder organisches Nitratsalz ein Nitrat der allgemeinen Formel [Kation⁺][NO₃ ^-] vorliegt, mit [Kation⁺] ausgewählt aus der Gruppe bestehend aus Na⁺, K⁺, Ammoniumionen mit der allgemeinen Struktur [R¹R²R³R⁴N⁺] mit R¹, R², R³, R⁴, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₆-Alkyl, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt, Imidazolium-Kationen mit der allgemeinen Struktur (I)
  
  mit R¹ und R², unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt, und R³ ausgewählt aus der Gruppe bestehend aus H und C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere aus der Gruppe bestehend aus H und C₁- bis C₈-Alkyl, geradkettig oder verzweigt,
  Pyridinium-Kationen mit der allgemeinen Struktur (II)
  
  mit R¹ ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt und R², R³ und R⁴, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus H und C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere aus der Gruppe bestehend aus H und C₁- bis C₈-Alkyl, geradkettig oder verzweigt, und Phosphoniumionen mit der allgemeinen Struktur [R^1aR^2aR^3aR^4aP⁺] mit R^1a, R^2a, R^3a, R^4a, unabhängig voneinander, jeweils ausgewählt aus der Gruppe bestehend aus C₁- bis C₁₆-Alkyl, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt.
• Ausführungsform 17: Verfahren nach Ausführungsform 16, wobei in den Imidazolium-Kationen der allgemeinen Formel (I) die Reste R¹ und R², unabhängig voneinander, jeweils ausgewählt sind aus der Gruppe bestehend aus C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere C₁- bis C₈-Alkyl, geradkettig oder verzweigt und R³ für Wasserstoff steht, vorzugsweise R¹ für Methyl und R² für Ethyl stehen oder R¹ für Methyl und R² für Methyl stehen und R¹ für Methyl und R² für Butyl stehen, sowie R³ jeweils für Wasserstoff steht.
• Ausführungsform 18: Verfahren nach Ausführungsform 16 oder 17, wobei in den Pyridinium-Kationen der allgemeinen Formel (II) der Rest R¹ für C₁- bis C₁₈-Alkyl, geradkettig oder verzweigt, insbesondere für C₁- bis C₈-Alkyl, geradkettig oder verzweigt steht und die Reste R², R³ und R⁴, unabhängig voneinander, jeweils ausgewählt sind aus der Gruppe bestehend aus C₁- bis C₈-Alkyl, geradkettig oder verzweigt, wobei eine einfache Substitution in 2-, 3- oder 4-Position, eine zweifache Substitution in 2,4-, 2,5- oder 2,6-Position oder eine dreifache Substitution in 2,4,6-Position bevorzugt ist.
• Ausführungsform 19: Verfahren nach einer der Ausführungsform 16 bis 18, wobei das organische Nitratsalz ausgewählt ist aus der Gruppe bestehend aus Tetra-n-butyl-ammonium-nitrat, Methyl-tri-n-octyl-ammonium-nitrat, Tetra-n-butyl-phosphonium-nitrat, Methyl-tri-n-octyl-phosphonium-nitrat und 1-Butyl-3-methylimidazoliumnitrat.
• Ausführungsform 20: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte Cycloalken und der unsubstituierte oder wenigstens einfach substituierte, gesättigte cycloaliphatische Kohlenwasserstoff vorgelegt und mit dem Reaktionsmedium zusammengebracht werden, vorzugsweise in dem Reaktionsmedium zumindest teilweise oder vollständig gelöst oder damit gemischt werden, und dann das anorganische oder organische Nitratsalz dazugegeben wird.
• Ausführungsform 21: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das anorganische oder organische Nitratsalz vorgelegt und mit dem Reaktionsmedium zusammengebracht werden, vorzugsweise in dem Reaktionsmedium zumindest teilweise oder vollständig gelöst oder damit gemischt wird, und dann das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte Cycloalken und der unsubstituierte oder wenigstens einfach substituierte, gesättigte cycloaliphatische Kohlenwasserstoff, vorzugsweise in Kombination, dazugegeben werden.
• Ausführungsform 22: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte Cycloalken und der unsubstituierte oder wenigstens einfach substituierte, gesättigte cycloaliphatische Kohlenwasserstoff und das anorganische oder organische Nitratsalz vorgelegt und dann mit dem Reaktionsmedium zusammengebracht werden, vorzugsweise in dem Reaktionsmedium zumindest teilweise oder vollständig gelöst oder damit gemischt werden.
• Ausführungsform 23: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das unsubstituierte oder wenigstens einfach substituierte, einfach oder mehrfach ungesättigte Cycloalken und der unsubstituierte oder wenigstens einfach substituierte, gesättigte cycloaliphatische Kohlenwasserstoff und das anorganische oder organische Nitratsalz gleichzeitig oder in zeitlicher Abfolge zueinander in das Reaktionsmedium gegeben werden, vorzugsweise in dem Reaktionsmedium zumindest teilweise oder vollständig gelöst oder damit gemischt werden.
• Ausführungsform 24: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das Reaktionsmedium ein polares aprotisches Reaktionsmedium ist, welches wasserfrei, getrocknet oder in Kombination mit Wasser vorliegen kann. Ausführungsform 25: Verfahren nach Ausführungsform 24, wobei der Gehalt an Wasser bis zu 20 Vol.-%, vorzugsweise bis zu 15 Vol.-%, besonders bevorzugt bis zu 10 Vol.-%, ganz besonders bevorzugt bis zu 5 Vol.-%, beträgt, jeweils bezogen auf die Gesamtmenge an Reaktionsmedium.
• Ausführungsform 26: Verfahren nach Ausführungsform 24 oder 25, wobei das polare aprotische Reaktionsmedium ausgewählt ist aus der Gruppe bestehend aus aliphatischen Nitrilen, aliphatischen Ketonen, cycloaliphatischen Ketonen, Dialkylcarbonaten, cyclischen Carbonaten, Lactonen, aliphatischen Nitroalkanen, und Dimethylsulfoxid, Estern und Ethern oder einer Kombination aus wenigstens zwei dieser Komponenten.
• Ausführungsform 27: Verfahren nach Ausführungsform 26, wobei als Reaktionsmedium ein polares aprotisches Reaktionsmedium vorliegt, welches ausgewählt ist aus der Gruppe bestehend aus Acetonitril, Isobutyronitril, Adiponitril, Aceton, Dimethylcarbonat, Methylethylketon, 3-Pentanon, Cyclohexanon, Nitromethan, Nitropropan, tert.-Butylmethylether, Dimethylsulfoxid, gamma-Butyrolacton und epsilon-Caprolacton oder einer Kombination aus wenigstens zwei dieser Komponenten, jeweils ggf. in Kombination mit Wasser.
• Ausführungsform 28: Verfahren nach Ausführungsform 27, wobei ein Reaktionsmedium ausgewählt aus der Gruppe bestehend aus Acetonitril, Isobutyronitril, Adiponitril, Dimethylcarbonat und Aceton oder einer Kombination aus wenigstens zwei dieser Komponenten, ggf. in Kombination mit Wasser, vorliegt.
• Ausführungsform 29: Verfahren nach Ausführungsform 27 oder 28. wobei das Reaktionsmedium Acetonitril, Isobutyronitril oder Adiponitril in getrockneter oder wasserfreier Form ist.
• Ausführungsform 30: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das Reaktionsmedium eine oder mehrere lösungsvermittelnde Komponenten aufweist.
• Ausführungsform 31: Verfahren gemäß Ausführungsform 30, wobei als lösungsvermittelnde Komponenten primäre Alkohole, sekundäre Alkohole, Monoketone oder Dialkylcarbonate oder Mischungen aus wenigstens zwei dieser Komponenten vorliegen, ggf. in Kombination mit Wasser.
• Ausführungsform 32: Verfahren gemäß Ausführungsform 30 oder 31, wobei aliphatische C_1-6-Alkohole als eine oder mehrere lösungsvermittelnde Komponenten vorliegen, vorzugsweise einer oder mehrere Alkohole ausgewählt aus der Gruppe bestehend aus Methanol, Ethanol, Isopropanol, 2-Methyl-2-Butanol und Mischungen aus wenigstens zwei dieser Komponenten, ggf. in Kombination mit Wasser. Ausführungsform 33: Verfahren gemäß einer der vorhergehenden Ausführungsformen, wobei als Reaktionsmedium Dimethylcarbonat, ggf. in Kombination mit wenigstens einem C_1-6-Alkohol, vorzugsweise ausgewählt aus der Gruppe bestehend aus Methanol, Ethanol, Isopropanol, 2-Methyl-2-Butanol vorliegt.
• Ausführungsform 34: Verfahren gemäß Ausführungsform 33, wobei das Reaktionsmedium Wasser aufweist.
• Ausführungsform 35: Verfahren gemäß einer der Ausführungsformen 30 bis 34, wobei eine oder mehrere lösungsvermittelnde Komponenten in einer Menge von < 50 Vol.-%, besonders bevorzugt von < 30 Vol.-% und ganz besonders bevorzugt von < 10 Vol.-% zugegeben werden, jeweils bezogen auf die Gesamtmenge an Reaktionsmedium vorliegen.
• Ausführungsform 36: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei das anorganische oder organische Nitratsalz in einer Menge von 0,1 bis 2,0, vorzugsweise 0,2 bis 1,0, besonders bevorzugt 0,3 bis 0,8 und ganz besonders bevorzugt 0,4 bis 0,8 Äquivalenten, bezogen auf die Menge an eingesetztem unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigte Cycloalken und in einer Menge von 0,8 bis 10,0, vorzugsweise 2,5 bis 10,0, besonders bevorzugt 3,0 bis 10,0 und ganz besonders bevorzugt 5,0 bis 10,0 Äquivalenten, bezogen auf die Menge an eingesetztem unsubstituierten oder wenigstens einfach substituierten, gesättigten cycloaliphatischen Kohlenwasserstoff eingesetzt wird.
• Ausführungsform 37: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei in räumlicher Verbindung mit dem Reaktionsmedium eine Gasatmosphäre enthaltend Sauerstoff bereitgestellt wird.
• Ausführungsform 38: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der Anteil von Sauerstoff an der Gasatmosphäre 10 bis 100 Vol.-%, vorzugsweise 15 bis 30 Vol.-%, besonders bevorzugt 15 bis 25 Vol.-%, ganz besonders bevorzugt 18 bis 22 Vol.-%, beträgt.
• Ausführungsform 39: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der Anteil von Sauerstoff an der Gasatmosphäre 10 bis 100 Vol.-% besonders bevorzugt 15 bis 100 Vol.-%, besonders bevorzugt 20 bis 100 Vol.-% beträgt.
• Ausführungsform 40: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Gasatmosphäre Luft ist.
• Ausführungsform 41: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei zwischen der Gasatmosphäre und dem Reaktionsmedium ein Gasaustausch erzwungen wird.
• Ausführungsform 42: Verfahren nach Ausführungsform 41, wobei der Gasaustausch durch das Einleiten von Gasatmosphäre in das Reaktionsmedium erfolgt. Ausführungsform 43: Verfahren nach Ausführungsform 41 oder 42, wobei der Gasaustausch durch Rühren der flüssigen Phase in Gegenwart der Gasatmosphäre erfolgt.
• Ausführungsform 44: Verfahren nach Ausführungsform 43, wobei das Rühren zur Steuerung der elektrochemischen Oxidation verwendet wird.
• Ausführungsform 45: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die im Reaktionsmedium gelöste Menge an Sauerstoff mindestens 1 mmol/L Reaktionsmedium beträgt.
• Ausführungsform 46: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die im Reaktionsmedium gelöste Menge an Sauerstoff mindestens 5 mmol/L Reaktionsmedium beträgt.
• Ausführungsform 47: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Elektrolysezelle eine ungeteilte Elektrolysezelle ist.
• Ausführungsform 48: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Elektrolysezelle eine Glaskohlenstoff-Anode, eine Graphit-Anode oder eine BDD-Anode, vorzugsweise eine Glaskohlenstoff-Anode aufweist.
• Ausführungsform 49: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Elektrolysezelle eine Glaskohlenstoff-Kathode, eine Graphit-Kathode oder eine BDD-Kathode, vorzugsweise eine Glaskohlenstoff-Kathode aufweist.
• Ausführungsform 50:
  • Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der Abstand der Elektroden in der Elektrolysezelle 0,1 mm bis 2,0 cm, vorzugsweise 0,1 mm bis 1,0 cm,
  • besonders bevorzugt 0,1 mm bis 0,5 cm beträgt.
• Ausführungsform 51: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die Ladungsmenge mindestens 190 C (2 F) bis 970 C (10 F), vorzugsweise 290 C (3 F) bis 870 C (9 F), besonders bevorzugt 330 C (3,5 F) bis 820 C (8,5 F), ganz besonders bevorzugt 380 C (4 F) bis 775 C (8 F), am meisten bevorzugt 380 C (4 F) bis 580 C (6 F), jeweils für 1 mmol an eingesetztem unsubstituierten oder wenigstens einfach substituierten, einfach oder mehrfach ungesättigten Cycloalken und unsubstituiertem oder wenigstens einfach substituiertem, gesättigten cycloaliphatischen Kohlenwasserstoff.
• Ausführungsform 52: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die elektrochemische Oxidation bei konstanter Stromstärke erfolgt. Ausführungsform 53: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 5 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 54: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 10 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 55: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 15 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 56: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 20 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 57: Verfahren nach einer der vorhergehenden Ausführungsformen, dadurch gekennzeichnet, dass die Stromdichte wenigstens 20 mA/cm² bis 50 mA/cm² beträgt, wobei sich die Flächenangabe auf die geometrische Fläche der Elektroden bezieht.
• Ausführungsform 58: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei der zur elektrochemischen Oxidation eingesetzte Strom aus regenerativen Quellen stammt, insbesondere aus Biomasse, Solarthermie, Geothermie, Wasserkraft, Windkraft oder Photovoltaik.
• Ausführungsform 59: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei die elektrochemische Oxidation bei einer Temperatur im Bereich von 0 bis 60 °C, vorzugsweise von 5 bis 50 °C, besonders bevorzugt von 10 bis 40°C, ganz besonders bevorzugt von 15-30°C erfolgt.
• Ausführungsform 60: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es unter Atmosphärendruck durchgeführt wird.
• Ausführungsform 61: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es unter Unterdruck durchgeführt wird.
• Ausführungsform 62: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es unter Überdruck, vorzugsweise bis zu 16 bar, besonders bevorzugt bis zu 6 bar durchgeführt wird.
• Ausführungsform 63: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es Batch-weise durchgeführt wird.
• Ausführungsform 64: Verfahren nach einer der vorhergehenden Ausführungsformen, wobei es kontinuierlich durchgeführt wird, vorzugsweise in einer ungeteilten Durchfluss-Elektrolysezelle.
• Ausführungsform 65: Verfahren nach einem der vorhergehenden Ausführungsformen, wobei es ohne den Zusatz von Katalysatoren, insbesondere ohne den Zusatz von Übergangsmetallkatalysatoren durchgeführt wird.
• Ausführungsform 66: Verfahren nach einem der vorhergehenden Ausführungsform, wobei neben Sauerstoff oder Luftsauerstoff keine weiteren Oxidationsmittel zugesetzt werden.

Further preferred embodiments of the present invention are the following embodiments:

• Embodiment 1: Process for producing unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids and unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation, comprising the process steps:
  • (a-1) providing at least one unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene;
  • (a-2) providing at least one unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon;
  • (b) providing at least one inorganic or organic nitrate salt;
  • (c) Electrochemical oxidation of the unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene provided in step (a-1) and the unsubstituted or at least mono-substituted, saturated cycloaliphatic provided in step (a-2). Hydrocarbon in the presence of the inorganic or organic nitrate salt provided in step (b) in an electrolysis cell in a reaction medium in the presence of oxygen.
• Embodiment 2: Process according to Embodiment 1, wherein the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene is monocyclic or bicyclic, preferably monocyclic.
• Embodiment 3: Process according to embodiment 1 or 2, wherein the unsubstituted or at least monosubstituted cycloalkene is monounsaturated, preferably monounsaturated and monocyclic.
• Embodiment 4: Method according to one of the preceding embodiments, wherein the unsubstituted or at least mono-substituted, mono- or polyunsaturated monocyclic cycloalkene has 5 to 12 C atoms, particularly preferably 6 to 12 C atoms, very particularly preferably 8 to 12 C atoms in the ring system and unsubstituted or substituted once or multiple times, preferably with 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl, the phenyl or benzyl substituents themselves being unsubstituted or are substituted once or multiple times, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ .
• Embodiment 5: Process according to one of the preceding embodiments 2 to 4, wherein the unsubstituted or at least mono-substituted, mono- or polyunsaturated bicyclic cycloalkene contains 7 to 18 C atoms, particularly preferably 7 to 12 C atoms, very particularly preferably 7 to 10 C atoms Ring system and are unsubstituted or substituted once or multiple times, preferably with 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl, the phenyl or benzyl substituents themselves are each unsubstituted or mono- or poly-substituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ .
• Embodiment 6: Process according to one of the preceding embodiments, wherein the cycloalkene is selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, 1-phenylcyclohex-1-ene, bicylo[2.2.1]hept- 2-ene, α-pinene and carene.
• Embodiment 7: Process according to one of the preceding embodiments, wherein the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon is monocyclic or bicyclic, preferably monocyclic.
• Embodiment 8: Process according to Embodiment 7, wherein the monocyclic or bicyclic, saturated cycloaliphatic hydrocarbon has 5 to 18 C atoms in the ring system and is unsubstituted or mono or polysubstituted with 1, 2, 3, 4 or 5 substituents, each selected independently of one another from the group consisting of methyl, phenyl or benzyl, where phenyl or benzyl can each be unsubstituted or mono or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and _NO2
• Embodiment 9: Process according to one of the preceding embodiments, wherein the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon is a monocyclic saturated hydrocarbon with 6 to 12 carbon atoms in the ring, preferably with 8 to 12 carbon atoms in the ring, this cycloaliphatic hydrocarbon being unsubstituted or is substituted once or multiple times with 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl, particularly preferably a monocyclic saturated hydrocarbon with 8 to 12 carbon atoms in the ring, this being cycloaliphatic Hydrocarbons are unsubstituted or mono- or di- or tri-substituted with methyl. Embodiment 10: Method according to one of the preceding embodiments, wherein the saturated cycloaliphatic hydrocarbon is selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane, preferably selected from the group consisting of cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane, particularly preferably cyclododecane.
• Embodiment 11: Process according to one of the preceding embodiments, wherein the cycloalkene is selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, 1-phenylcyclohex-1-ene, bicylo[2.2.1]hept- 2-ene, α-pinene and carene and wherein the saturated cycloaliphatic hydrocarbon is selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane.
• Embodiment 12: The method according to embodiment 11, wherein the cycloalkene is cyclododecene and wherein the saturated cycloaliphatic hydrocarbon is cyclododecane.
• Embodiment 13: Method according to one of the preceding embodiments, wherein the provision of at least one unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene according to step (a-1) and the provision of at least one unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbon according to step (a-1) a-2) in combination, preferably as a mixture.
• Embodiment 14: Process according to one of the preceding embodiments, wherein the molar proportion of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene is 40 to 95 mol%, preferably 45 to 55 mol%, particularly preferably 47 to 53 mol. -%, based on the total amount of unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene and unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbon used.
• Embodiment 15: Process according to one of the preceding embodiments, wherein the molar proportion of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene is >60 mol%, preferably >65 mol%, particularly preferably >70 mol% , in each case based on the total amount of unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene and unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbon used. Embodiment 16: Method according to one of the preceding embodiments, wherein the inorganic or organic nitrate salt is a nitrate of the general formula [cation ⁺ ][NO ₃ ^- ], with [cation ⁺ ] selected from the group consisting of Na ⁺ , K ⁺ , ammonium ions with the general structure [R ¹ R ² R ³ R ⁴ N ⁺ ] with R ¹ , R ² , R ³ , R ⁴ , independently of one another, each selected from the group consisting of C ₁ - to C ₁₆ -alkyl, in particular C ₁ - to C ₈ alkyl, straight chain or branched, imidazolium cations with the general structure (I)
  
  with R ¹ and R ² , independently of one another, each selected from the group consisting of C ₁ - to C ₁₈ alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, and R ³ selected from Group consisting of H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -alkyl, straight-chain or branched,
  Pyridinium cations with the general structure (II)
  
  with R ¹ selected from the group consisting of C ₁ - to C ₁₈ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched and R ² , R ³ and R ⁴ , independently of one another, each selected from the group consisting from H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -alkyl, straight-chain or branched, and phosphonium ions with the general structure [R ^1a R ^2a R ^3a R ^4a P ⁺ ] with R ^1a , R ^2a , R ^3a , R ^4a , independently of one another, each selected from the group consisting of C ₁ - to C ₁₆ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched .
• Embodiment 17: Process according to Embodiment 16, wherein in the imidazolium cations of the general formula (I), the radicals R ¹ and R ² , independently of one another, are each selected from the group consisting of C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - to C ₈ alkyl, straight-chain or branched and R ³ is hydrogen, preferably R ¹ is methyl and R ² is ethyl or R 1 is methyl and R ² is methyl and R ^{1 is} methyl and R ² represents butyl and R ³ each represents hydrogen.
• Embodiment 18: Process according to embodiment 16 or 17, wherein in the pyridinium cations of the general formula (II) the radical R ¹ is C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl , straight-chain or branched and the radicals R ² , R ³ and R ⁴ , independently of one another, are each selected from the group consisting of C ₁ - to C ₈ -alkyl, straight-chain or branched, with a simple substitution in 2-, 3 - or 4-position, a double substitution in the 2,4-, 2,5- or 2,6-position or a triple substitution in the 2,4,6-position is preferred.
• Embodiment 19: The method according to any one of embodiments 16 to 18, wherein the organic nitrate salt is selected from the group consisting of tetra- n -butyl ammonium nitrate, methyl tri- n- octyl ammonium nitrate, tetra- n -butyl -phosphonium nitrate, methyl tri- n -octyl phosphonium nitrate and 1-butyl-3-methylimidazolium nitrate.
• Embodiment 20: Process according to one of the preceding embodiments, wherein the unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene and the unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbon are introduced and brought together with the reaction medium, preferably at least partially or completely in the reaction medium are dissolved or mixed with it, and then the inorganic or organic nitrate salt is added.
• Embodiment 21: Method according to one of the preceding embodiments, wherein the inorganic or organic nitrate salt is introduced and brought together with the reaction medium, preferably at least partially or completely dissolved in the reaction medium or mixed with it, and then the unsubstituted or at least monosubstituted, single or multiple unsaturated cycloalkene and the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon, preferably in combination, are added.
• Embodiment 22: Process according to one of the preceding embodiments, wherein the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon and the inorganic or organic nitrate salt are introduced and then brought together with the reaction medium, preferably be at least partially or completely dissolved in the reaction medium or mixed with it.
• Embodiment 23: Process according to one of the preceding embodiments, wherein the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and the unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon and the inorganic or organic nitrate salt are added to the reaction medium simultaneously or in time succession to one another are, preferably at least partially or completely dissolved in the reaction medium or mixed with it.
• Embodiment 24: Method according to one of the preceding embodiments, wherein the reaction medium is a polar aprotic reaction medium, which can be anhydrous, dried or in combination with water. Embodiment 25: Process according to embodiment 24, wherein the water content is up to 20% by volume, preferably up to 15% by volume, particularly preferably up to 10% by volume, very particularly preferably up to 5% by volume. , is based on the total amount of reaction medium.
• Embodiment 26: Process according to Embodiment 24 or 25, wherein the polar aprotic reaction medium is selected from the group consisting of aliphatic nitriles, aliphatic ketones, cycloaliphatic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, and dimethyl sulfoxide, esters and ethers or a combination from at least two of these components.
• Embodiment 27: Process according to Embodiment 26, wherein the reaction medium is a polar aprotic reaction medium which is selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, acetone, dimethyl carbonate, methyl ethyl ketone, 3-pentanone, cyclohexanone, nitromethane, nitropropane, tert. Butyl methyl ether, dimethyl sulfoxide, gamma-butyrolactone and epsilon-caprolactone or a combination of at least two of these components, each optionally in combination with water.
• Embodiment 28: Process according to Embodiment 27, wherein a reaction medium selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, dimethyl carbonate and acetone or a combination of at least two of these components, optionally in combination with water, is present.
• Embodiment 29: Process according to Embodiment 27 or 28, wherein the reaction medium is acetonitrile, isobutyronitrile or adiponitrile in dried or anhydrous form.
• Embodiment 30: Method according to one of the preceding embodiments, wherein the reaction medium has one or more solubilizing components.
• Embodiment 31: Process according to Embodiment 30, wherein the solubilizing components are primary alcohols, secondary alcohols, monoketones or dialkyl carbonates or mixtures of at least two of these components, optionally in combination with water.
• Embodiment 32: Method according to embodiment 30 or 31, wherein aliphatic C _1-6 alcohols are present as one or more solubilizing components, preferably one or more alcohols selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol and mixtures of at least two of these components, possibly in combination with water. Embodiment 33: Process according to one of the preceding embodiments, wherein the reaction medium is dimethyl carbonate, optionally in combination with at least one C _1-6 alcohol, preferably selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol .
• Embodiment 34: Method according to Embodiment 33, wherein the reaction medium comprises water.
• Embodiment 35: Method according to one of embodiments 30 to 34, wherein one or more solubilizing components are added in an amount of <50% by volume, particularly preferably <30% by volume and most preferably <10% by volume are present, based on the total amount of reaction medium.
• Embodiment 36: Method according to one of the preceding embodiments, wherein the inorganic or organic nitrate salt is in an amount of 0.1 to 2.0, preferably 0.2 to 1.0, particularly preferably 0.3 to 0.8 and most preferably 0.4 to 0.8 equivalents, based on the amount of unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene used and in an amount of 0.8 to 10.0, preferably 2.5 to 10.0, particularly preferred 3.0 to 10.0 and very particularly preferably 5.0 to 10.0 equivalents, based on the amount of unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon used.
• Embodiment 37: Method according to one of the preceding embodiments, wherein a gas atmosphere containing oxygen is provided in spatial connection with the reaction medium.
• Embodiment 38: Method according to one of the preceding embodiments, wherein the proportion of oxygen in the gas atmosphere is 10 to 100 vol.%, preferably 15 to 30 vol.%, particularly preferably 15 to 25 vol.%, very particularly preferably 18 to 22% by volume.
• Embodiment 39: Method according to one of the preceding embodiments, wherein the proportion of oxygen in the gas atmosphere is 10 to 100% by volume, particularly preferably 15 to 100% by volume, particularly preferably 20 to 100% by volume.
• Embodiment 40: Method according to one of the preceding embodiments, wherein the gas atmosphere is air.
• Embodiment 41: Method according to one of the preceding embodiments, wherein a gas exchange is forced between the gas atmosphere and the reaction medium.
• Embodiment 42: Method according to Embodiment 41, wherein the gas exchange takes place by introducing a gas atmosphere into the reaction medium. Embodiment 43: Method according to embodiment 41 or 42, wherein the gas exchange takes place by stirring the liquid phase in the presence of the gas atmosphere.
• Embodiment 44: The method according to Embodiment 43, wherein stirring is used to control electrochemical oxidation.
• Embodiment 45: Method according to one of the preceding embodiments, wherein the amount of oxygen dissolved in the reaction medium is at least 1 mmol/L reaction medium.
• Embodiment 46: Method according to one of the preceding embodiments, wherein the amount of oxygen dissolved in the reaction medium is at least 5 mmol/L reaction medium.
• Embodiment 47: Method according to one of the preceding embodiments, wherein the electrolytic cell is an undivided electrolytic cell.
• Embodiment 48: Method according to one of the preceding embodiments, wherein the electrolysis cell has a glassy carbon anode, a graphite anode or a BDD anode, preferably a glassy carbon anode.
• Embodiment 49: Method according to one of the preceding embodiments, wherein the electrolysis cell has a glassy carbon cathode, a graphite cathode or a BDD cathode, preferably a glassy carbon cathode.
• Embodiment 50:
  • Method according to one of the preceding embodiments, wherein the distance between the electrodes in the electrolysis cell is 0.1 mm to 2.0 cm, preferably 0.1 mm to 1.0 cm,
  • particularly preferably 0.1 mm to 0.5 cm.
• Embodiment 51: Method according to one of the preceding embodiments, wherein the amount of charge is at least 190 C (2 F) to 970 C (10 F), preferably 290 C (3 F) to 870 C (9 F), particularly preferably 330 C (3. 5 F) to 820 C (8.5 F), most preferably 380 C (4 F) to 775 C (8 F), most preferably 380 C (4 F) to 580 C (6 F), each for 1 mmol of unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene and unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon used.
• Embodiment 52: Method according to one of the preceding embodiments, wherein the electrochemical oxidation takes place at constant current intensity. Embodiment 53: Method according to one of the preceding embodiments, characterized in that the current density is at least 5 mA/cm ² , the area information relating to the geometric area of the electrodes.
• Embodiment 54: Method according to one of the preceding embodiments, characterized in that the current density is at least 10 mA/cm ² , the area information relating to the geometric area of the electrodes.
• Embodiment 55: Method according to one of the preceding embodiments, characterized in that the current density is at least 15 mA/cm ² , the area information referring to the geometric area of the electrodes.
• Embodiment 56: Method according to one of the preceding embodiments, characterized in that the current density is at least 20 mA/cm ² , the area information relating to the geometric area of the electrodes.
• Embodiment 57: Method according to one of the preceding embodiments, characterized in that the current density is at least 20 mA/cm ² to 50 mA/cm ² , the area information relating to the geometric area of the electrodes.
• Embodiment 58: Method according to one of the preceding embodiments, wherein the electricity used for electrochemical oxidation comes from renewable sources, in particular from biomass, solar thermal energy, geothermal energy, hydropower, wind power or photovoltaics.
• Embodiment 59: Method according to one of the preceding embodiments, wherein the electrochemical oxidation takes place at a temperature in the range from 0 to 60 ° C, preferably from 5 to 50 ° C, particularly preferably from 10 to 40 ° C, very particularly preferably from 15-30 °C takes place.
• Embodiment 60: Method according to one of the preceding embodiments, wherein it is carried out under atmospheric pressure.
• Embodiment 61: Method according to one of the preceding embodiments, wherein it is carried out under negative pressure.
• Embodiment 62: Method according to one of the preceding embodiments, wherein it is carried out under excess pressure, preferably up to 16 bar, particularly preferably up to 6 bar.
• Embodiment 63: Method according to one of the preceding embodiments, wherein it is carried out in batches.
• Embodiment 64: Method according to one of the preceding embodiments, wherein it is carried out continuously, preferably in an undivided flow electrolysis cell.
• Embodiment 65: Process according to one of the preceding embodiments, wherein it is carried out without the addition of catalysts, in particular without the addition of transition metal catalysts.
• Embodiment 66: Method according to one of the preceding embodiments, wherein no further oxidizing agents are added in addition to oxygen or atmospheric oxygen.

The following examples further illustrate the present invention but are not to be construed as limiting the scope of the invention.

General information and methods

Analytical grade chemicals were purchased and used from mainstream suppliers (such as TCI, Aldrich, and Acros). The oxygen was purchased in 2.5 quality from NIPPON GASES Deutschland GmbH, Düsseldorf, Germany and used directly.

Glassy carbon (SIGRADUR ^® G, from HTW Hochtemperatur Werkstoffe GmbH, Thierhaupten, Germany) was used as the electrode material.

High-performance liquid chromatography was carried out on a Shimadzu HPLC-MS with a SIL 20A HT autosampler, a CTO-20AC column oven, two LC-20AD pump modules for gradient adjustment of the eluent, a diode array detector SPD-M20A, a CBM-20A system controller, and a Eurospher II 100-5 C18 column (150 x 4 mm, Knauer, Berlin). Eluent: acetonitrile (ACN) / water / formic acid (1 vol.%) (from 10% ACN to 90% ACN in 10 min + 10 min 100% ACN). Mass spectrometric measurements were carried out on an LCMS-2020 Shimadzu, Japan. NMR spectrometry of ¹ H-NMR and ¹³ C-NMR spectra were carried out at 25 °C with a Bruker Avance II 400 (400 MHz, 5 mm BBFO head with z-gradient and ATM, SampleXPress 60 sample changer, Analytische Messtechnik, Karlsruhe, Germany).

Gas chromatographic studies were carried out on a Shimadzu GC-2025 (Shimadzu, Japan), which was equipped with an HP 5MS column (Agilent Technologies, Santa Clara, California; length: 30 m, inner diameter: 0.25 mm, film thickness: 0.25 µm, Carrier gas: hydrogen). GC-MS measurements were carried out on a Shimadzu GC-2010 (Shimadzu, Japan) equipped with an HP-1 column (Agilent Technologies, Santa Clara, California; length: 30 m, inner diameter: 0.25 mm, film thickness: 0.25 µm, carrier gas : helium). To prepare samples for GC analysis, column filtration over silica gel 60 M (0.04-0.063 mm, Macherey-Nagel GmbH & Co. KG, Düren, Germany) was carried out.

The undivided Teflon cells used for electrolysis are described in the literature (a) C. Gütz, B. Klöckner, SR Waldvogel, Org. Process Res. Dev. 2016, 20, 26-32 ; b) A. Kirste, G. Schnakenburg, F. Stecker, A. Fischer, SR Waldvogel, Angew. Chem. Int. Ed. 2010, 49, 971-975 ; Angew. Chem. 2010, 122, 983-987 . (see SI).) The complete range of these cells is commercially available from IKA Screening System (IKA-Werke GmbH & Co. KG, Staufen, Germany). The dimensions of the electrodes were 7 cm x 1 cm x 0.3 cm.

The gas introduction was controlled via two mass flow controllers (MFC) model 5850S from Brooks Instrument BV, Veenendaal, Netherlands. A regulator was used for the oxygen and nitrogen lines. The controllers were controlled using the Smart DDE and Matlab R2017b software. The volume flow control was also carried out using a DK800 variable area flowmeter from KROHNE Messtechnik GmbH, Duisburg. For all experiments carried out, the total volume flow was a constant 20 mL/min, which, limited by the MFCs used, also represents the maximum achievable volume flow. The percentage volume flows of the two gases were set using the MFCs and their software. The gas bottles were used from the following suppliers: oxygen 2.5 from NIPPON GASES Deutschland GmbH, Düsseldorf, and nitrogen 4.8 from Westfalen AG, Münster and nitrogen 5.0 from NIPPON GASES Deutschland GmbH, Düsseldorf. The gas distributor and the gas inlet covers of the electrolysis cells are described in the literature (M. Dörr, D. Waldmann, SR Waldvogel, GIT Labor-Fachz. 2021, 7-8, 26-28) and were manufactured by IKA (IKA-Werke GmbH & Co .KG, Staufen, Germany).

General working instructions AAV1

The cycloalkane (0.1 to 0.5 mmol), the cycloalkene (0.5 to 0.9 mmol, cumulative alkane and alkene to a total of 1 mmol) and tetrabutylammonium nitrate (0.5 eq. ) and dissolved in acetonitrile or isobutyronitrile (5 mL). The cell was equipped with glassy carbon electrodes at a distance of 0.5 cm. The immersion area of the electrodes is 1.8 cm ² . After the cell was fixed in a stainless steel block, galvanostatic electrolysis was performed at a current density of 10 mA/cm ² at 22 °C.

The application of the charge amount referred to the theoretical charge amounts for the oxidation of both components, depending on their ratio (alkane/alkene = 0.1/0.9: 7.6 F; 0.25/0.75: 7.0 F; 0.5/0.5: 6.0F). After electrolysis, 1,3,5-trimethoxybenzene (10 mg) was added to the reaction solution as an internal standard. Three drops were removed and filtered through silica gel 60 M (eluent: ethyl acetate). The filtrate was collected in a GC vial and examined by gas chromatography. The solvent was first removed from the remaining reaction solution by distillation. The conductive salt was then removed extractively using 10 mL of ethyl acetate and 10 mL of aqueous HCl solution (0.1 M). The solvent in the organic phase was removed by distillation and the residue was taken up with an aqueous NaOH solution (1 M, 10 mL). The aqueous phase was washed with 10 mL of diethyl ether. After phase separation, the aqueous phase was adjusted to pH 1 with an aqueous HCl solution (1 M) and extracted from this with 2 × 10 mL ethyl acetate. After drying the organic phase over sodium sulfate and removing the solvent by distillation, the dicarboxylic acid product was dried under high vacuum.

After applying the charge amount, 10 mg of 1,3,5-trimethoxybenzene is added to the reaction solution as an internal standard. 3 drops of the reaction solution are removed for gas chromatographic analysis and quantification of the product. These are eluted using ethyl acetate over approx. 330 mg of 60 M silica gel. Approximately 1.5 mL of the filtrate is collected in a GC vial, which is examined for oxidation products using GC-FID and GC-MS. The quantification was carried out via a previous calibration of the gas chromatograph.

example 1

Tabelle 1: Reaktionen zur Co-Elektrolyse Substrate Mischungsverhältnisse Produkte C: Cyclooctanon^[d] D: Octandisäure^[e] n = 3 A:B = 1:9 (10 mol% A)^[a] 4% 40% A:B = 1:3 (25 mol% A)^[b] 2% 44% A:B = 1:1 (50 mol% A)^[c] 2% 45% C: Cyclododecanon^[d] D: Dodecandisäure^[e] n = 7 A:B = 1:9 (10 mol% A)^[a] 27% 57% A:B = 1:3 (25 mol% A)^[b] 13% 63% A:B = 1:1 (50 mol% A)^[c] 9% 74% Für n = 3 wurde Acetonitril und für n = 7 Isobutyronitril als Lösungsmittel verwendet. Kumulierte Ladungsmengen bezgl. A und B: a) 7,6 F; b) 7,0 F; c) 6,0 F. d) Bestimmung mittels externer GC-Kalibrierung (interner Standard: 1,3,5-Trimethoxybenzol). e) Isolierte Ausbeuten. Alle Ausbeuten beziehen sich auf die eingesetzten Stoffmengen des jeweiligen Eduktes. According to AAV1, the following co-electrolyses were performed (Scheme 1, Table 1).

<b>Table 1:</b> Reactions for co-electrolysis Substrates Mixing ratios Products C: Cyclooctanone ^[d] D: Octanedioic acid ^[e] n = 3 A:B = 1:9 (10 mol% A ) ^[a] 4% 40% A:B = 1:3 (25 mol% A ) ^[b] 2% 44% A:B = 1:1 (50 mol% A ) ^[c] 2% 45% C: Cyclododecanone ^[d] D: Dodecanedioic acid ^[e] n = 7 A:B = 1:9 (10 mol% A ) ^[a] 27% 57% A:B = 1:3 (25 mol% A ) ^[b] 13% 63% A:B = 1:1 (50 mol% A ) ^[c] 9% 74% Acetonitrile was used as solvent for n = 3 and isobutyronitrile for n = 7. Cumulative charge quantities regarding A and B: a) 7.6 F; b) 7.0F ; c) 6.0F . d) Determination using external GC calibration (internal standard: 1,3,5-trimethoxybenzene). e) Isolated yields. All yields relate to the amounts of the respective starting material used.

Claims (15)

Process for the preparation of unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids and unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation, comprising the process steps: (a-1) providing at least one unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene; (a-2) providing at least one unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon; (b) providing at least one inorganic or organic nitrate salt; (c) electrochemical oxidation of the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated cycloalkene provided in step (a-1) and the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon provided in step (a-2) in the presence of the one provided in step (a-2). b) provided inorganic or organic nitrate salt in an electrolysis cell in a reaction medium in the presence of oxygen. The method according to claim 1, wherein the unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene is monocyclic or bicyclic, wherein preferably the unsubstituted or at least mono-substituted, mono- or polyunsaturated monocyclic cycloalkene has 5 to 12 C atoms, particularly preferably 6 to 12 C Atoms, most preferably 8 to 12 C atoms in the ring system and are unsubstituted or substituted once or multiple times, preferably with 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl , where the phenyl or benzyl substituents themselves are each unsubstituted or mono- or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ and/or the unsubstituted or at least monosubstituted, monounsaturated or polyunsaturated bicyclic cycloalkene has 7 to 18 C atoms, particularly preferably 7 to 12 C atoms, very particularly preferably 7 to 10 C atoms in the ring system and is unsubstituted or mono or polyunsaturated, preferably with 1, 2 , 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl, the phenyl or benzyl substituents themselves being unsubstituted or mono- or polysubstituted, with 1, 2 or 3 substituents, independently of one another, each selected from the group consisting of F, Cl, Br, and NO ₂ . Method according to one of the preceding claims, wherein the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon is monocyclic or bicyclic, wherein the monocyclic or bicyclic, saturated cycloaliphatic hydrocarbon preferably has 5 to 18 C atoms in the ring system and is unsubstituted or mono or polysubstituted with 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl, where phenyl or benzyl can each be unsubstituted or mono or polysubstituted, with 1, 2 or 3 substituents, independently from each other, each selected from the group consisting of F, Cl, Br, and NO ₂ Method according to one of the preceding claims, wherein the unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon is a monocyclic saturated hydrocarbon with 6 to 12 carbon atoms in the ring, preferably with 8 to 12 carbon atoms in the ring, this cycloaliphatic hydrocarbon being unsubstituted or mono or multiple is substituted with 1, 2, 3, 4 or 5 substituents, independently of one another, each selected from the group consisting of methyl, phenyl or benzyl. Method according to one of the preceding claims, wherein the cycloalkene is selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, 1-phenylcyclohex-1-ene, bicylo[2.2.1]hept-2-ene , α-pinene and carene and wherein the saturated cycloaliphatic hydrocarbon is selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane and cyclododecane. Method according to one of the preceding claims, wherein the inorganic or organic nitrate salt is a nitrate of the general formula [cation ⁺ ][NO ₃ ^- ] is present, with [cation ⁺ ] selected from the group consisting of Na ⁺ , K ⁺ , ammonium ions with the general structure [R ¹ R ² R ³ R ⁴ N ⁺ ] with R ¹ , R ² , R ³ , R ⁴ , independently each other, each selected from the group consisting of C ₁ - to C ₁₆ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, imidazolium cations with the general structure (I)

with R ¹ and R ² , independently of one another, each selected from the group consisting of C ₁ - to C ₁₈ alkyl, straight-chain or branched, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched, and R ³ selected from Group consisting of H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -alkyl, straight-chain or branched,
Pyridinium cations with the general structure (II)

with R ¹ selected from the group consisting of C ₁ - to C ₁₈ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched and R ² , R ³ and R ⁴ , independently of one another, each selected from the group consisting from H and C ₁ - to C ₁₈ -alkyl, straight-chain or branched, in particular from the group consisting of H and C ₁ - to C ₈ -alkyl, straight-chain or branched, and phosphonium ions with the general structure [R ^1a R ^2a R ^3a R ^4a P ⁺ ] with R ^1a , R ^2a , R ^3a , R ^4a , independently of one another, each selected from the group consisting of C ₁ - to C ₁₆ -alkyl, in particular C ₁ - to C ₈ -alkyl, straight-chain or branched . Method according to one of the preceding claims, wherein the reaction medium is a polar aprotic reaction medium, optionally in Combination with water, wherein in the combination with water the water content is preferably up to 20% by volume, particularly preferably up to 15% by volume, very particularly preferably up to 10% by volume, even more preferably up to 5 % by volume, based on the total amount of reaction medium. The method according to claim 7, wherein the reaction medium is a polar aprotic reaction medium which is selected from the group consisting of aliphatic nitriles, aliphatic ketones, cycloaliphatic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, and dimethyl sulfoxide, esters and ethers or a combination from at least two of these components, preferably from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, acetone, dimethyl carbonate, methyl ethyl ketone, 3-pentanone, cyclohexanone, nitromethane, nitropropane, tert-butyl methyl ether, dimethyl sulfoxide, gamma-butyrolactone and epsilon-caprolactone or one Combination of at least two of these components, each possibly in combination with water. Method according to one of the preceding embodiments, wherein the inorganic or organic nitrate salt is in an amount of 0.1 to 2.0, preferably 0.2 to 1.0, particularly preferably 0.3 to 0.8 and most preferably 0.4 to 0.8 equivalents, based on the amount of unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene used and in an amount of 0.8 to 10.0, preferably 2.5 to 10.0, particularly preferably 3.0 to 10.0 and very particularly preferably 5.0 to 10.0 equivalents, based on the amount of unsubstituted or at least monosubstituted, saturated cycloaliphatic hydrocarbon used. Method according to one of the preceding claims, wherein a gas atmosphere containing oxygen is provided in spatial connection with the reaction medium, the proportion of oxygen in the gas atmosphere preferably being 10 to 100% by volume, particularly preferably 15 to 30% by volume, very particularly preferably 15 to 25% by volume, most preferably 18 to 22% by volume. A method according to claim 11, wherein a gas exchange is forced between the gas atmosphere and the reaction medium, preferably by introducing gas atmosphere into the reaction medium or by stirring the reaction medium in the presence of the gas atmosphere. Method according to one of the preceding claims, wherein the amount of charge is at least 190 C (2 F) to 970 C (10 F), preferably 290 C (3 F) to 870 C (9 F), particularly preferably 330 C (3.5 F) to 820 C (8.5 F), very particularly preferably 380 C (4 F) to 775 C (8 F), most preferably 380 C (4 F) to 580 C (6 F), in each case for 1 mmol of used unsubstituted or at least mono-substituted, mono- or polyunsaturated cycloalkene and unsubstituted or at least mono-substituted, saturated cycloaliphatic hydrocarbon. Method according to one of the preceding claims, wherein the current density is at least 5 mA/cm ² , the area information relating to the geometric area of the electrodes. Method according to one of the preceding claims, wherein the electrolytic cell is an undivided cell. Method according to one of the preceding claims, wherein it is carried out batchwise or continuously, preferably continuously in an undivided flow electrolysis cell.