DE102019109443A1 - Cyandiazohydroxide and processes for their preparation - Google Patents

Abstract

The present invention relates to cyandiazohydroxides and processes for their preparation.

Description

The present invention relates to cyandiazohydroxides and processes for their preparation.

The nitrosation of primary amines from the aromatic series is well known. Aniline reacts, for example, with nitrosating reagents to form various products depending on the pH value. In acidic reaction media (pH value <6.5) the phenyldiazonium cation is formed, which is of great importance in the manufacture of azo dyes. In neutral reaction media (pH 6.5 to 7.5), phenyldiazohydroxide is formed, which is stereochemically in syn or anti conformation (also referred to as Z / E form) and / or in its tautomeric form as N-nitrosoaniline . In alkaline media (pH> 7.5) the phenyldiazohydroxide is deprotonated to the phenyldiazotate anion, which also shows E / Z stereoisomerism (Houben-Weyl Methods of Organic Chemistry, 4th Edition, Volume 10/3 (1965 ) Page 551 ff).

Aryldiazonium salts can be converted into aryldiazocyanides by reaction with cyanides. These occur analogously in two positionally isomeric forms (referred to as syn and anti or Z and E form), which have different physical properties and are easily converted into one another (Houben-Weyl Methods of Organic Chemistry, 4th Edition, Volume 10 / 3 (1965) page 593 ff).

The products of the nitrosation of primary aliphatic amines are much more difficult to grasp, since the primarily formed nitrosamines easily dehydrate with protonation to aliphatic diazonium salts, which in turn decompose very easily with the elimination of nitrogen to form highly reactive alkyl cations or their secondary products. Aliphatic diazo compounds, which are derived from the elusive diazen HN = NH, are also very sensitive and usually cannot be produced by nitrosation reactions (Houben-Weyl Methods of Organic Chemistry, 4th Edition, Volume 10/2 (1967) page 761 ff) . Electrophilically substituted, e.g. B. aliphatic diazo compounds bearing acyl groups show very considerable differences in terms of their stability and are, for. Sometimes even explosive (Houben-Weyl Methods of Organic Chemistry, 4th Edition, Volume 10/2 (1967) page 807 ff). The most stable of these compounds, azodicarbonamide can be z. B. by oxidation of the corresponding hydrazine derivative and is commercially used as an industrial chemical.

Diazene-dicarbonitrile, on the other hand, can only be obtained by dimerization of cyanitrene, e.g. B. by decomposition of cyanazide, produce and forms very decomposable orange-red needles with a melting point of 35 ° C (cf. DE 12 06 911 B ).

The compound N, N'-dihydroxydiazene, usually referred to as hypositrous acid, can only be isolated in a stable manner in the trans form (also referred to as E or anti stereoisomer) and forms hygroscopic, very explosive crystals (AF Holleman, E. Wiberg, N. Wiberg: Textbook of Inorganic Chemistry. 101st edition. De Gruyter, Berlin 1995, ISBN 3-11-012641-9). The trans isomer forms relatively stable salts, while the cis isomer only in the form of salts, e.g. B. the disodium salt or the lead salt is known ( C. Feldmann et.al., Zeitschrift für Anorganische und Allgemeine Chemie (1997), 623 (11), 1803-1809 ).

Compounds of the formula R-N = N-OH with an aliphatic radical R are largely unknown since they are preferably in the - likewise unstable - nitrosamine form.

Alkyl diazocyanides of the formula RN = N-CN with an aliphatic radical R are unknown, although their existence has been predicted theoretically ( K. Morihashi et. al., Journal of Molecular Structure: THEOCHEM (2001), 543, 233-241 ).

There are only a few and contradicting references to compounds of the structural units N = CN = NOR from the literature. H. Koehler et. al. (Zeitschr. Anorg. Allg. Chem., (1970) 379,183) describe the reaction of sodium hydrogen cyanamide with nitrosyl chloride and silver nitrate in absolute diethyl ether at a temperature of -10 ° C. to form a silver salt of what is known there as cyanaminonitrite (today's nomenclature: N'-cyandiazotate ) in 30% yield. The silver salt is only stable at low temperatures and slowly splits off nitrogen (N ₂ ) even at room temperature. The only characterization given for the silver salt is an IR absorption band at 2175 cm ^-1 . Koehler et al. thus describe the silver salt of cyandiazohydroxide, although there is no indication of the possible existence of stereoisomeric, free cyandiazohydroxides.

Furthermore, T. Fuchigami et.al. (Denki Kagaku oyobi Kogyo Butsuri Kagaku (1976) 44, 803) the electrochemical reduction of nitrocyanamide to what is called nitrosocyanamide there, which is not isolated or characterized. A reaction with potassium or silver salts led to isolable potassium or silver salts of nitrosocyanamide. The two easily decomposable salts were characterized by their elemental composition and an IR absorption band at 2150, 2200 cm ^-1 (ṽ C≡N). From this publication it could be concluded that a nitrosocyanamide exists which can at least be isolated as a potassium or silver salt. Fuchigami et al. give no indication of the possible existence of stereoisomeric free cyandiazohydroxides.

G. Olah (J. Org. Chem. (1985) 50, 1338) describes the nitrosation of cyanamide with nitrosyl tetrafluoroborate. He mentions the cyandiazonium cation (or a precursor complex) as a hypothetical intermediate product, which quickly decomposes with the elimination of nitrogen. From these statements, too, there is no indication of the existence of cyandiazohydroxides.

The present invention is therefore based on the object of providing aliphatic diazo hydroxides which can be prepared preparatively and can be adequately characterized and, due to their properties, represent starting materials which are easy to handle for further chemical reactions. A further object of the invention is to provide compounds and / or mixtures thereof which can be handled safely and which can be used as starting material in further syntheses. In addition, one object is to provide a technically applicable process for the preparation of aliphatic diazo hydroxides.

The basic tasks are achieved by a mixture consisting of E-cyandiazohydroxide according to formula (I), hereinafter also referred to as E-1, and Z-cyandiazohydroxide according to formula (II), hereinafter also referred to as Z-1, where for formula (I ) and (II) apply

As the following statements show, these compounds are present as a mixture of isomers because of their rapid conversion with one another. It should be emphasized at this point that the conceivable - and according to the statements on the prior art actually to be expected - nitroso form (N-nitrosocyanamide) is not observed and is not detectable in addition to the mixture consisting of E-1 and Z-1.

A mixture consisting of E-cyandiazohydroxide according to formula (I) and Z-cyandiazohydroxide according to formula (II) in which the molar ratio of E-1 to Z-1 is a ratio in the range from 1: 1 to 20: 1 is preferred 1: 1 to 15: 1, particularly preferably 5: 1 to 15: 1.

These cyandiazohydroxides are surprisingly easy to prepare, can be handled without problems in aqueous solution and, due to their characteristic decomposition pathways, can find technical application with the formation of useful products.

Thus, according to a further embodiment, the present invention also relates to a solution, in particular a water-containing solution, comprising a mixture consisting of E-cyandiazohydroxide according to formula (I) and Z-cyandiazohydroxide according to formula (II). A solution, in particular a water-containing solution, comprising a mixture consisting of E-1 and Z-1, which has a molar ratio of E-1 to Z-1 in the range from 1: 1 to 20: 1, is particularly preferred 1: 1 to 15: 1, particularly preferably 5: 1 to 15: 1.

Furthermore, a solution, in particular a water-containing solution, comprising a mixture consisting of E-cyandiazohydroxide according to formula (I) and Z-cyandiazohydroxide according to formula (II) is the subject of the present invention, which the mixture in an amount of 1 to 200 g / l, in particular 1 to 150 g / l and very particularly preferably 1 to 120 g / l.

Cyanamide (CH ₂ N ₂ ; CAS No. 420-04-2) can be considered one of the simplest primary aliphatic amines. Surprisingly, it has been found that cyanamide reacts with nitrosating reagents in a manner analogous to primary aromatic amines to form cyanide azohydroxides according to formula (I) and formula (II). The products resulting from this reaction are still, especially in water or water-containing products Solutions, surprisingly stable and manageable, so that these products are helpful in technical applications and can be used as intermediates in chemical synthesis.

und wobei in einem ersten Verfahrensschritt 1 eine Komponente 1 umfassend

1. a) Cyanamid, oder
2. b) Chlorformamidin oder ein Salz hiervon, oder
3. c) ein Gemisch aus
   1. i) Cyanamid und eine Säure, oder
   2. ii) Cyanamid und Chlorformamidin, oder
   3. iii) Cyanamid und ein Chlorformamidin-Salz, oder
   4. iv) Cyanamid, Chlorformamidin und ein Chlorformamidin-Salz,

und separat hiervon eine Komponente 2 umfassend ein Nitrosierungsreagenz bereitgestellt werden, und in einem zweiten Verfahrensschritt 2 die bereitgestellten Komponente 1 und Komponente 2 bei einer Temperatur im Bereich von - 20 bis + 10 °C in Wasser oder in einem Wasser-haltigen Reaktionsmedium miteinander umgesetzt werden.und separat hiervon eine Komponente 2 umfassend ein Nitrosierungsreagenz bereitgestellt werden, und in einem zweiten Verfahrensschritt 2 die bereitgestellten Komponente 1 und Komponente 2 bei einer Temperatur im Bereich von - 20 bis + 10 °C in Wasser oder in einem Wasser-haltigen Reaktionsmedium miteinander umgesetzt werden.Thus, a method for producing a mixture consisting of E-cyandiazohydroxide according to formula (I) and Z-cyandiazohydroxide according to formula (II), or a method for producing a solution, in particular a water-containing solution, comprising a mixture consisting of E. -Cyandiazohydroxide according to formula (I) and Z-cyandiazohydroxide according to formula (II), the subject of the present invention, where for formula (I) and (II) applies

and wherein in a first method step 1 comprising a component 1

1. a) cyanamide, or
2. b) chlorformamidine or a salt thereof, or
3. c) a mixture of
   1. i) cyanamide and an acid, or
   2. ii) cyanamide and chloroformamidine, or
   3. iii) cyanamide and a chloroformamidine salt, or
   4. iv) cyanamide, chlorformamidine and a chlorformamidine salt,

and separately therefrom a component 2 comprising a nitrosation reagent is provided, and in a second process step 2 the provided component 1 and component 2 are reacted with one another at a temperature in the range from -20 to + 10 ° C in water or in a water-containing reaction medium .and separately therefrom a component 2 comprising a nitrosation reagent are provided, and in a second process step 2 the provided component 1 and component 2 are reacted with one another at a temperature in the range from -20 to + 10 ° C in water or in a water-containing reaction medium will.

Cyanamide can be obtained as an aqueous solution or in crystalline form. Usually it contains a stabilizer which z. B. based on salts or esters of phosphoric acid or formic acid. This stabilizer does not hinder the preparation according to the invention of the compounds of the formulas (I) and (II). Thus, in the process according to the invention, cyanamide can be used as a solid or as a solution, in particular as an aqueous solution.

Chlorformamidine (CH ₃ N ₂ Cl; CAS-6869-14-3) can be produced by known methods. For example, the hydrochloride of chlorformamidine (CH ₄ N ₂ Cl; CAS 29671-92-9) can be used according to DE 19 15 668 from anhydrous cyanamide and anhydrous hydrogen chloride. The free base of chlorformamidine decomposes in the reverse of the synthetic route to cyanamide and HCl and thus serves as a synthon for cyanamide and as an acid supplier.

According to the present invention, chlorformamidine hydrochloride, chlorformamidine hydrobromide, chlorformamidine nitrate, chlorformamidine sulfate and chlorformamidine hydrogen sulfate can be used as the chlorformamidine salt. Chlorformamidine hydrochloride is preferred.

Nitrosation reagents for the preparation of the compounds according to the invention are in particular reagents from the group of nitrous acid, which can also be used as an aqueous or non-aqueous solution, dinitrogen trioxide, a mixture of nitrogen monoxide and nitrogen dioxide, nitrosyl chloride, nitrosyl sulfuric acid, alkali metal nitrites, in particular sodium nitrite and potassium nitrite, optionally in the presence of an acid, and esters of nitrous acid with aliphatic alcohols with 1 to 6 Carbon atoms, especially butyl nitrite, pentyl nitrite and isopentyl nitrite are suitable. Particularly preferred nitrosation reagents are sodium nitrite, potassium nitrite, butyl nitrite, pentyl nitrite and isopentyl nitrite.

The use of nitrosyl tetrafluoroborate, in particular when used as a nitrosating reagent, is not covered by the present invention, since its toxicity and its corrosion caused by fluoride, inter alia. of glass, in which synthesis is very disadvantageous.

According to the present invention, component 1 is reacted with one or more of the nitrosation reagents mentioned in water or in a water-containing reaction medium, in particular a water-containing polar solvent. In the investigations on which this invention is based, in particular solvents, in particular polar solvents, from the group of water, aliphatic alcohols with 1 to 6 carbon atoms, in particular methanol, ethanol, n-propanol, iso-propanol, n-butanol, 2-butanol, n Pentanol or n-hexanol, aliphatic ethers with a total of 2 to 8 carbon atoms, in particular diethyl ether, methyl ethyl ether, aliphatic nitriles with 2 to 5 carbon atoms, especially acetonitrile, chlorinated hydrocarbons with 1 to 4 carbon atoms and 2 to 6 chlorine atoms, in particular Dichloromethane, shown to be suitable. Of these solvents, water, diethyl ether, dichloromethane and acetonitrile are particularly preferred.

An additional acid can be used when reacting cyanamide with the nitrosation reagent, especially if this is present as an alkali salt. The pKa value of the acid used is preferably less than 6.0, particularly preferably less than 5.0. Mineral acids and carboxylic acids are suitable as acids. According to the present invention, sulfuric acid, alkanesulfonic acids, hydrochloric acid, anhydrous hydrogen chloride and alkanecarboxylic acids, in particular acetic acid or formic acid, are particularly preferred.

For the reaction of cyanamide and optionally acid with the nitrosating reagent, at least one component is preferably added in a metered manner. This can be either the cyanamide and optionally the acid or the nitrosating reagent. But it is also possible to dose two components in parallel. The submitted components are preferably dissolved in the selected solvent, the components to be metered in pure, gaseous or liquid form, dissolved in the solvent or added in portions in solid form. It is not preferred to mix the nitrosating reagent with the acid without the presence of cyanamide as a reactant, since nitrous gases would then be formed.

The stoichiometric ratio between cyanamide and nitrosating reagent is preferably 1: 2 to 2: 1, particularly preferably 1: 1.2 to 1.2: 1. The stoichiometric ratio of acid to nitrosating reagent is preferably 0: 1 to 2: 1, particularly preferably 0: 1 to 1.2: 1.

A mixture of the compounds of formula (I) and (II) is preferably prepared in aqueous solution by reacting cyanamide with an acid, in particular hydrochloric acid or acetic acid, and an alkali nitrite, in particular sodium nitrite (NaNO ₂ ) or potassium nitrite (KNO ₂ ) Temperatures in the temperature range from -20 to +10 ° C.

If the compounds of the formula (I) or (II) according to the invention or a mixture thereof are to be stored after preparation, this should take place at temperatures from -50 to +20.degree.

1. 1) durch eine gelblichgrüne Färbung der wässrigen oder nichtwässrigen Lösung;
2. 2) durch ein charakteristisches, pH-abhängiges UV-Spektrum mit einer starken Absorption bei λ_max = 260 nm mit ε₂₆₀ im Bereich von 500 bis 800 m²/mol bei pH-Werten von 3 bis 10 und einer schwächeren UV-Absorption bei λ_max = 370 nm mit ε₃₇₀ im Bereich von 2 bis 4 m²/mol;
3. 3) durch ein charakteristisches chromatographisches Verhalten mit UV-Detektion bei 260 nm. In schwach saurer, neutraler oder schwach alkalischer Lösung (pH > 2,0) zeigt das chromatographische Signal auf einer polaren reversed-phase-Säule zwei isomere, elektrisch neutrale Moleküle identischer UV-Absorption an. In stark saurer Lösung (pH < 2,0) werden die Verbindungen der Formel (I) und (II) protoniert und ergeben ein Kation, welches mit der Totzeit eluiert;
4. 4) durch ihr Massenspektrum gemessen mittels LC/ESI-MS mit einem charakteristischen M+1-Peak von 72 Masseneinheiten im Positiv-Modus und einem M-1-Peak von 70 Masseneinheiten im Negativ-Modus;
5. 5) durch ihre charakteristischen Raman-Absorptionsbanden in wässriger Lösung bei 2180 bis 2250 cm^-1 (C≡N-Bande), bei 1360 bis 1390 cm^-1 (N=N-Bande) und bei 1180 bis 1220 cm^-1 (N-O-Bande);
6. 6) durch Fällung eines hellgelben Silbersalzes aus saurer, wässriger Lösung. Dieses Silbersalz ist leicht zersetzlich und zeigt im IR eine charakteristische Bande bei 2170 bis 2180 cm^-1 (C≡N-Bande);
7. 7) durch ihre charakteristischen ¹³C-NMR-Sinale bei 114 ppm (E-Cyandiazohydroxid) und 122 ppm (Z-Cyandiazohydroxid) in D₂O-Lösung;
8. 8) durch ihre charakteristischen ¹⁴N- oder ¹⁵N-NMR-Signale bei -172, -68 und +236 ppm (E-Cyandiazohydroxid) bzw. bei -160, -102 und +184 ppm (Z-Cyandiazohydroxid), gemessen in D₂O gegen Nitromethan als interner Standard bei 0 ppm;
9. 9) durch die Abwesenheit von charakteristischen Signalen, die für Nitrosoverbindungen typisch sind. Dies sind im IR und Raman z. B. die N=O-Streckschwingungsbanden bei ca. 1430 bis 1480 cm^-1, im Stickstoff-NMR Signale im Bereich von ca. +300 bis +500 ppm, bezogen auf Nitromethan als Standard; sowie
10. 10) durch ihre charakteristischen Zersetzungsprodukte. Bei pH-Werten oberhalb 2,0 entsteht bei der thermischen Zersetzung der Cyandiazohydroxide der Formel (I) bzw. (II) vorzugsweise Distickstoffmonoxid zusammen mit Blausäure bzw. Cyaniden. Im stark sauren Bereich, unterhalb pH 2,0 werden die Cyandiazohydroxide hingegen protoniert und nach Wasserabspaltung zum Cyandiazonium-Kation umgewandelt, welches thermisch unter Bildung von Elementarstickstoff zerfällt. Dieses pH-abhängige Zersetzungsverhalten ist einzigartig und charakterisiert so die erfindungsgemäßen Verbindungen.

The compounds of the formula (I) and (II) can be characterized as follows:

1. 1) by a yellowish-green coloration of the aqueous or non-aqueous solution;
2. 2) by a characteristic, pH-dependent UV spectrum with a strong absorption at λ _max = 260 nm with ε ₂₆₀ in the range from 500 to 800 m ² / mol at pH values from 3 to 10 and a weaker UV absorption λ _max = 370 nm with ε ₃₇₀ in the range from 2 to 4 m ² / mol;
3. 3) by a characteristic chromatographic behavior with UV detection at 260 nm. In a weakly acidic, neutral or weakly alkaline solution (pH> 2.0) the chromatographic signal on a polar reversed-phase column shows two isomeric, electrically neutral molecules that are identical UV absorption on. In a strongly acidic solution (pH <2.0), the compounds of the formula (I) and (II) are protonated and give a cation which elutes with the dead time;
4. 4) by its mass spectrum measured by LC / ESI-MS with a characteristic M + 1 peak of 72 mass units in positive mode and an M-1 peak of 70 mass units in negative mode;
5. 5) by their characteristic Raman absorption bands in aqueous solution at 2180 to 2250 cm ^-1 (C≡N band), at 1360 to 1390 cm ^-1 (N = N band) and at 1180 to 1220 cm ^-1 (NO -Band);
6. 6) by precipitation of a light yellow silver salt from acidic, aqueous solution. This silver salt is easily decomposable and shows a characteristic band in the IR at 2170 to 2180 cm ^-1 (C≡N band);
7. 7) by their characteristic ¹³ C-NMR sinals at 114 ppm (E-cyandiazohydroxide) and 122 ppm (Z-cyandiazohydroxide) in D ₂ O solution;
8. 8) by their characteristic ¹⁴ N or ¹⁵ N NMR signals at -172, -68 and +236 ppm (E-cyandiazohydroxide) and at -160, -102 and +184 ppm (Z-cyandiazohydroxide), measured in D ₂ O against nitromethane as internal standard at 0 ppm;
9. 9) by the absence of characteristic signals typical of nitroso compounds. These are in IR and Raman z. B. the N = O stretching vibration bands at approx. 1430 to 1480 cm ^-1 , in the nitrogen NMR signals in the range from approx. +300 to +500 ppm, based on nitromethane as standard; as
10. 10) by their characteristic decomposition products. At pH values above 2.0, the thermal decomposition of the cyandiazohydroxides of the formula (I) or (II) preferably forms nitrous oxide together with hydrocyanic acid or cyanides. In the strongly acidic range, below pH 2.0, on the other hand, the cyandiazohydroxides are protonated and, after splitting off water, converted to the cyandiazonium cation, which thermally decomposes with the formation of elementary nitrogen. This pH-dependent decomposition behavior is unique and thus characterizes the compounds according to the invention.

The mixtures of E-1 and Z-1 produced in this way are particularly suitable for use as a starting material in the synthesis of organic compounds. Thus, these mixtures can be used in particular as reagents in organic synthesis, in particular in the cyanation of aromatic hydrocarbons.

Thus, another component of the invention is the technical use of the mixtures of E-1 and Z-1 for the simple and safe production of substances that are otherwise difficult to produce, such as. B. nitrous oxide and / or hydrocyanic acid or cyanide.

The newly found cyandiazohydroxides according to the invention are suitable for a wide variety of technical and synthetic applications. For example, the thermal decomposition at pH> 2 enables the simple production of nitrous oxide from a water-containing solution at low temperatures. At pH <2, nitrogen can be generated in a targeted and metered manner. Both gases can serve as blowing agents or foaming agents, or they can be provided for further chemical conversion.

Thermal decomposition at pH> 2 gives cyanide or hydrocyanic acid in good yield. Cyanides are difficult to handle because of their toxicity. The new substances according to the invention make it possible to produce cyanides in a targeted manner in a spatially and temporally defined manner, only relatively non-toxic raw materials having to be reacted with one another under mild conditions. Cyanide or hydrogen cyanide are z. B. commonly used as pesticides or disinfectants and as such difficult to handle.

At pH values <2, the thermal decomposition of the substances according to the invention enables a reactive C≡N synthon to be provided, which is capable of electrophilic cyanation. For example, it can cyanate aromatic hydrocarbons to aromatic nitriles, convert cyanamide to dicyanamide or provide a simple synthesis of dicyan gas starting from cyanides. Thus, cyandiazohydroxides of the formula (I) and (II) can be used in many different ways in organic synthesis, both in isolated form, e.g. B. in solution, as well as a reagent, which is only produced in-situ.

If the compounds of the formula (I) or (II) according to the invention or their mixture are to be reacted further without isolation in situ, without or in the presence of an additional substrate molecule, the synthesis of the new compound is preferably carried out at temperatures from 0 to 140 ° C, particularly preferably at 40 to 100 ° C. The higher temperatures compared to the first procedure are useful in order to avoid an accumulation of the easily decomposable, gas-evolving compounds (I) or (II).

If the compounds of the formula (I) or (II) or a mixture thereof are first prepared in a two-stage process and then reacted further in a second step, the second step is carried out at 0 to 140 ° C, preferably at 40 to 100 ° C.

The present invention thus also encompasses the use of a mixture containing E-1 and Z-1 or a solution, in particular an aqueous solution, comprising a mixture containing E-1 and Z-1 for the cyanation of aromatic carbocycles.

The following examples are intended to explain the essence of the invention in more detail.

Examples

Example 1:

Preparation of an aqueous solution of E-cyan diazohydroxide according to formula (I) (hereinafter E-1) and Z-cyan diazohydroxide according to formula (II) (hereinafter Z-1) in the presence of acetic acid (with parallel dosing)

6,9 g (0,1 mol) Natriumnitrit wurden in 50 g Wasser gelöst. Bei 0 °C wurde zu dieser Lösung während 1 Stunde 4,2 g (0,1 mol) festes Cyanamid, gelöst in 20 g Wasser und 6,0 g (0,1 mol) Essigsäure, gelöst in 20 g Wasser parallel aus zwei Tropftrichtern zugetropft. Nach einer Stunde Nachreaktion bei 0 °C wurden 107 g einer 0,93-molaren Lösung erhalten. Die Lösung war klar, hatte einen pH-Wert von 3,1, eine gelbgrüne Farbe und blieb bei 0 °C über 48 Stunden stabil. Bei 20 °C zeigten sich nach 15 Minuten erste Gasblasen, die auf eine beginnende Zersetzung hindeuten.

6.9 g (0.1 mol) of sodium nitrite were dissolved in 50 g of water. At 0 ° C., 4.2 g (0.1 mol) of solid cyanamide, dissolved in 20 g of water and 6.0 g (0.1 mol) of acetic acid, dissolved in 20 g of water, were added to this solution in parallel over 1 hour Dropped dropping funnels. After one hour of post-reaction at 0 ° C., 107 g of a 0.93 molar solution were obtained. The solution was clear, had a pH of 3.1, a yellow-green color and remained stable at 0 ° C. for 48 hours. At 20 ° C, the first gas bubbles appeared after 15 minutes, indicating the beginning of decomposition.

UV spectroscopy of E-1 and Z-1

A solution prepared according to 1.1 was adjusted to pH 5.0 by adding a small amount of sodium hydroxide solution and diluted with water to 50 times the initial volume (sample 1 : 50). A portion of this sample was diluted 100-fold with more water (sample 1 : 5000). The UV spectrum of both solutions was measured in a 1 cm cuvette (see 1 ). There is a strong UV absorption at 260 nm with an extinction coefficient of ε ₂₆₀ = 726 m ² / mol and a weak absorption at 370 nm with an extinction coefficient ε ₃₇₀ of 2.96 m ² / mol, which is only when diluted 1 : 50 was clearly visible.

In a second experiment, a solution prepared according to 1.1 was diluted by a factor of 1: 5000 and adjusted to the desired pH value by adding small amounts of sulfuric acid or sodium hydroxide solution. The UV spectrum of each of these solutions was measured in a 1 cm cuvette and the extinction at 260 nm plotted against the measured pH value (see 2 ). The result was a pH-dependent extinction curve which gives an acid constant (pKa) of approx. 1.8 for E-1 and Z-1.

HPLC content determination of E-1 and Z-1

A solution prepared according to 1.1 was diluted 100-fold with water. Using a 50 millimolar ammonium acetate buffer with pH 4.0 as the mobile phase, an injection volume of 10 μl, an HPLC column Hydrosphere C18 and UV detection at 260 nm, a chromatogram was performed according to 3 receive. The chromatogram shows a double peak with an area ratio of 92: 8. The UV spectra of both partial peaks obtained with a diode array detector were identical and corresponded to the UV spectrum from 1.2. If the pH of the mobile phase was reduced, the retention time was shifted forward, at pH <2 the peak was eluted with the dead time.

The result shows that the solution prepared according to 1.1 is composed of two chemically similar species, namely E-1 and Z-1. The pH-dependent retention behavior agrees with the pKa value determined in 1.2.

LC-MS data for E-1 and Z-1

A solution freshly prepared according to 1.1 was analyzed in an HPLC-MS-UV system. A 50 millimolar formic acid was used as the mobile phase, and a Hydrosphere C18 was used as the separation column. In the positive mode a mass m / Z = 72 was detected, in the negative mode a mass m / Z = 70. This agrees with the masses of E-1 and Z-1 of 71 g / mol. A parallel run of positive and negative mode together with a UV track at 260 nm (see 4th ) shows a perfect match between retention times and peak shape.

Production and characterization of the silver salt

10.7 g (0.01 mol) of a solution prepared according to 1.1 with a pH of 3.1 were mixed with 5 ml of a 1 molar silver nitrate solution at 0 ° C. A light yellow, crystalline precipitate formed. This was carefully filtered off, washed with ethanol and diethyl ether and carefully air-dried. It proved to be very sensitive to impact, with smoke development and discoloration from yellow to gray, but without an audible bang.

The infrared spectrum of the silver salt was measured in an ATR measuring cell (see 5 ). The cyano band at 2177 cm ^-1 and the N = N band at 1441 cm ^-1 are characteristic of the structure of a cyandiazo compound.

Example 2:

Preparation of an aqueous solution of E-1 and Z-1 in the presence of acetic acid (successive dosing)

6.9 g (0.1 mol) of sodium nitrite and 4.2 g (0.1 mol) of solid cyanamide were dissolved in 70 g of water. At 0 ° C., 6.0 g (0.1 mol) of acetic acid, dissolved in 20 g of water, were added dropwise to this solution over 1 hour. After one hour of post-reaction at 0 ° C., 107 g of a 0.93 molar solution were obtained. The solution was visually and analytically indistinguishable from the solution from Example 1.

2.2 ¹³ C-NMR spectrum of E-1 and Z-1

A solution according to Example 2.1 was freshly prepared using D ₂ O instead of normal water. The ¹³ C-NMR spectrum can be found in 6th . In addition to the expected signals for acetate, there are two cyano-C signals at 114.4 and 122.0 ppm, which agree with the expected values for E-1 and Z-1. The peak area ratio of about 2: 1 deviates from that of the HPLC experiments from Example 1.3, which indicates a mutual conversion and a solvent-dependent equilibrium between E-1 and Z-1.

2.3 ¹⁴ N-NMR spectrum of E-1 and Z-1

A solution according to 2.1 was freshly prepared using D ₂ O instead of normal water. The ¹⁴ N-NMR spectrum can be found in 7th . Nitromethane with 0 ppm was used as a reference. The spectrum shows 3 signal pairs at -171.0 and -159.7 ppm, at -68.2 and -101.7 ppm and at +236.8 and +184.5 ppm, each with a peak area ratio of approx. 2: 1 was observed. The signal positions agree with the expected values for E-1 and Z-1 in a ratio of 2: 1. In particular, no signal was found in the 300 to 500 ppm range, which would indicate nitroso groups.

Example 3:

Preparation of an aqueous solution of E-1 and Z-1 in the presence of sulfuric acid

6.9 g (0.1 mol) of sodium nitrite and 4.2 g (0.1 mol) of solid cyanamide were dissolved in 70 g of water. At 0 ° C., 24.5 g (0.05 mol) of 20% strength sulfuric acid were added dropwise to this solution over the course of 1 hour. After one hour of post-reaction at 0 ° C., 105.6 g of a 0.95 molar solution were obtained.

The solution had a pH of 1.50 and the same yellow-green color as that from Example 1.1, but began to decompose more quickly and at lower temperatures with evolution of gas.

An HPLC content determination gave the same double peak as in 1.3. The concentration of E-1 and Z-1 was evaluated relative to a freshly prepared solution from Example 1.1 as a reference standard and was 83%.

Example 4:

Preparation of an aqueous solution of E-1 and Z-1 in the presence of hydrochloric acid (using chlorformamidine hydrochloride)

5.75 g (0.05 mol) of chlorformamidine hydrochloride and 2.1 g (0.05 mol) of solid cyanamide were dissolved in 50 g of water. Chlorformamidine hydrochloride served as a source for cyanamide and HCl in a molar ratio of 1: 2. 6.9 g (0.1 mol) of sodium nitrite dissolved in 20 g of water were added dropwise to this solution at 0 ° C. After one hour of post-reaction at 0 ° C., 84.5 g of a 1.18 molar solution were obtained. The solution had a pH of 1.53, the same yellow-green color as that from Example 1.1, but began to decompose more quickly and at lower temperatures with evolution of gas.

An HPLC content determination gave the same double peak as in 1.3. The concentration of E-1 and Z-1 was evaluated relative to a freshly prepared solution from Example 1.1 as a reference standard and was 93%.

Raman spectra of E-1 and Z-1

The Raman spectra of freshly prepared aqueous solutions according to Example 1.1 or Example 4.1 were measured with red laser excitation (see 8th - Solution from 1.1 and 9 - Solution from 4.1). A characteristic cyano band can be seen at approx. 2185 cm ^-1 , the spectrum of the solution from Example 4.1 being poorly resolved because of the onset of decomposition. Heating the solutions from Example 1.1 and 4.1 for 1 hour each time at 80 ° C. caused the cyano bands mentioned to disappear completely.

Example 5:

Decomposition of E-1 and Z-1 to gaseous products with HPLC tracking

A solution prepared according to Example 1.1 was gradually heated to 60 ° C. From 40 ° C, a uniform, easily controllable evolution of gas started. A total of 2200 ml of gas volume at 980 mbar and 21 ° C. was obtained from 0.1 mol of solution, the evolution of gas ceasing after 145 minutes. The evolved gas was sampled at regular intervals and analyzed for nitrous oxide. In the first gas sample 4.0 vol% N ₂ O 77 vol% N found, in the final gas sample ₂ O. Parallel samples were drawn from the remaining solution. The pH rose steadily from 3.0 initially to 6.3. The residual content of E-1 and Z-1 measured by HPLC fell proportionally to the amount of gas evolved (see 10 ). The area ratio of the HPLC double peak remained at 92: 8 throughout the decomposition reaction. This proves that the species detected by HPLC is identical to the gas-evolving species and suggests that the stereoisomeric E-1 and Z-1 rapidly convert into one another.

The mother liquor remaining at the end was analyzed for cyanide. A total of 0.042 mol of cyanide was found, which corresponds to a yield of 42% based on the cyanamide used. Further hydrogen cyanide was found in the shut-off liquid of the gasometer used as well as in the collected gas containing N ₂ O.

Small amounts of dicyanamide, which were formed by electrophilic cyanation of residual cyanamide, were found in the solution. In the gas sample collected, small amounts of dicyan (oxalic acid dinitrile) were found, which were formed by electrophilic cyanation of hydrogen cyanide (or cyanide) which was formed at the same time.

Decomposition of E-1 and Z-1 at constant pH 5

100 g of a 1 molar sodium phosphate buffer of pH 5.0 were initially charged at 80.degree. To this, 26.8 (0.025 mol) of a solution according to Example 1.1 were added dropwise over 1 hour. There was a spontaneous, violent evolution of gas. The gas was passed through a reflux condenser into a gasometer and then analyzed by GC. 583 ml of gas with a composition of 89% N ₂ O, 2% CO ₂ and 9% N _{2 were} obtained.

The remaining mother liquor including condensate was analyzed for cyanide. 3.4 g / liter of cyanide were found, which corresponds to 0.021 mol of hydrogen cyanide. The cyanide yield was thus 84%.

The decomposition of E-1 and Z-1 at pH 5 accordingly provides dinitrogen monoxide and hydrogen cyanide in good yields. Due to the simple way of producing them from raw materials that are easy to handle, these can be used industrially.

Decomposition of E-1 and Z-1 at pH 0

100 g of 1 molar sulfuric acid were initially introduced at 80.degree. To this, 26.8 (0.025 mol) of a solution according to Example 1.1 were added dropwise. At a pH of 0 ± 0.1 there was a spontaneous, violent evolution of gas. The gas was passed through a reflux condenser into a gasometer and then analyzed by GC. 793 ml of gas with a composition of 0.1% N ₂ O, 29% CO ₂ and 71% N _{2 were} obtained. Only 6.4 mg / liter of cyanide were found in the mother liquor including condensate.

At pH 0, there is no longer any E-1 or Z-1, but rather these are protonated and dehydrated to the cyandiazonium cation, so that the composition of the gaseous decomposition products deviates significantly from 5.2.

Kinetic data for the decomposition of E-1 and Z-1 at pH 5

Test 5.2 was repeated analogously with a phosphate buffer of pH 5.0. The solution from Example 1.1 was added quickly in different batches at different temperatures in the range from 60 to 90.degree. The gas volume then developed as a function of time was measured. A rate constant k for the decomposition of E-1 and Z-1 to form gaseous components (essentially N ₂ O) was determined based on the total volume obtained after the evolution of gas had ceased.

A plot of ln (k) against the reciprocal absolute temperature according to Arrhenius (see Table 1 and 11 ) resulted in a slope of 13.2 K ^-1 , which corresponds to an activation energy of 110 kJ / mol. The decomposition of E-1 or Z-1 to N ₂ O and HCN thus has a low activation energy.

Kinetic data of the decomposition of E-1 and Z-1 at pH 0

Investigation 5.3 was repeated analogously with 1 molar sulfuric acid. The solution from Example 1.1 was added quickly at different temperatures in the range from 40 to 80 ° C. The evaluation was carried out analogously to investigation 5.4, with the gaseous products being composed essentially of N ₂ and CO ₂ . A plot of ln (k) against the reciprocal absolute temperature according to Arrhenius (see Table 1 and 11 ) resulted in a slope of 6.5 K ^-1 , which corresponds to an activation energy of 54 kJ / mol. The decomposition of the cyandiazonium cation formed from E-1 or Z-1 in strongly acidic solutions to form N ₂ and CN ⁺ (or their secondary products, such as CO ₂ ) therefore has an extremely low activation energy. Table 1: Kinetic data and Arrhenius plot of the decomposition of the solution from Example 1.1 at pH 0 or pH 5 in the temperature range 40 to 90 ° C PH value Temperature (° C) Velocity constant from gas evolution rate (k) Half-life for the educt cyandiazohydroxide (minutes) reciprocal temperature multiplied by 1000 (1 / Kelvin) negative natural logarithm of the rate constant (- In (k)) 0 40 0.0661 10.49 3.1949 2.7166 0 50 0.1059 6.55 3.0960 2.2455 0 60 0.2190 3.17 3.0030 1.5187 0 70 0.3569 1.94 2.9155 1.0303 0 80 0.6846 1.01 2.8329 0.3789 5 60 0.0048 144.14 3.0030 5.3373 5 70 0.0178 39.05 2.9155 4.0314 5 80 0.0518 13.38 2.8329 2.9604 5 90 0.1277 5.43 2.7548 2.0584

Example 6:

Preparation of E-1 and Z-1 in diethyl ether solution using nitrosyl chloride

31.9 g of a solution of 1.94 g (0.03 mol) of nitrosyl chloride and 32 g of diethyl ether were mixed with 5.0 g of a solution of 1.92 g (0.03 mol) of solid cyanamide and 3 at -10 ° C , 1 g of diethyl ether added. A yellow-green solution was formed which showed an intense C≡N absorption band at 2226 cm ⁻¹ in the infrared. Careful evaporation of this solution at 0 to 20 ° C. led to complete decomposition with formation of gas, the mentioned IR band disappearing.

If an aliquot of the ethereal solution was shaken out with water and the aqueous extract was then subjected to HPLC according to Example 1.3, the presence of E-1 and Z-1 in a ratio of approx. 9: 1 could be detected using the retention time and the characteristic UV spectrum will. The yield of E-1 and Z-1 was approx. 85%.

Preparation of E-1 and Z-1 in dichloromethane solution using a nitrous acid ester

2.52 g (0.06 mol) of solid cyanamide were dissolved in 50 g of dichloromethane. At 0 ° C., 5.86 g (0.05 mol) of isopentyl nitrite were added dropwise to this and the mixture was stirred for 1 hour until the reaction was complete. The yellow-green solution showed little gas evolution. In the infrared spectrum, the freshly prepared solution showed an intense band at 2219 cm ^-1 . This band disappeared with increasing gas evolution at 20 ° C.

An aliquot of the freshly prepared solution was shaken out with water and the aqueous extract was examined by means of HPLC as in Example 1.3. Based on the retention time and the characteristic UV spectrum, the presence of E-1 and Z-1 in a ratio of approx. 9: 1 was detected. The yield was> 80%.

Reaction of a non-aqueous solution of E-1 and Z-1 with an aromatic hydrocarbon to form an aromatic nitrile

A freshly prepared solution according to Example 6.2 was admixed with 12.0 g (0.1 mol) of 1,3,5-trimethylbenzene. The mixture was then heated to 42 ° C. for 3 hours, during which time vigorous evolution of gas occurred and the yellow-green color of the solution disappeared. The reaction mixture obtained was extracted several times with water to remove isoamyl alcohol formed. The remaining dichloromethane solution contained essentially only unreacted 1,3,5-trimethylbenzene and 2,4,6-trimethylbenzonitrile formed in a ratio of 65:35. The cyanation yield was thus approx. 70%.

Cyanation of an aromatic hydrocarbon, here p-xylene, by E-1 and Z-1 formed in situ

1.26 g (0.03 mol) of solid cyanamide and 3.45 g (0.03 mol) of solid chlorformamidine hydrochloride were dissolved or suspended in 50 g of dichloromethane. 5.30 g (0.05 mol) of p-xylene were added to this. At 0 ° C., 3.45 g (0.05 mol) of solid sodium nitrite were then added in 10 portions, distributed over 1 hour. The suspension turned yellow-green in color and showed little gas evolution. The mixture was then heated to 42 ° C. and further reacted with vigorous, slowly subsiding evolution of gas, the yellow-green color disappearing. The suspension obtained was filtered to remove precipitated sodium chloride and the solvent was distilled off. 4.8 g of a brown crude product with a content of 71% 2,5-dimethylbenzonitrile were obtained.

Cyanation of an aromatic hydrocarbon (here polystyrene) by in-situ formed E-1 and Z-1

5.2 g linear polystyrene was dissolved in 55 g dichloromethane. 2.52 g (0.06 mol) of solid cyanamide were added to the solution. 5.86 g (0.05 mol) of isopentyl nitrite were metered in at 0 ° C., and the solution turned yellow-green. The mixture was then heated to 42 ° C., during which there was vigorous evolution of gas and the yellow-green color disappeared. After one hour, 30 g of ethanol were added as a precipitant, a polymeric, sticky solid precipitating out. This was filtered off, washed with ethanol and then washed several times with hot water. After drying at 78 ° C. in vacuo (27 mbar), 5.5 g of a solid polymer were obtained.

In the ATR infrared spectrum, the product showed, in addition to the bands characteristic of polystyrene, an intense C = N band at 2223 cm ⁻¹ . After pyrolysis at 600 ° C., the pyrolysate was examined by means of GC / MS. In addition to styrene, the 3 isomeric ortho-, meta- and para-cyanstyrenes were found in significant quantities. The product produced can therefore be described as polystyrene-co-cyanostyrene.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 1206911 B [0005]
• DE 1915668 [0022]

Non-patent literature cited

• C. Feldmann et.al., Zeitschrift für Anorganische und Allgemeine Chemie (1997), 623 (11), 1803-1809 [0006]
• K. Morihashi et. al., Journal of Molecular Structure: THEOCHEM (2001), 543, 233-241 [0008]

Claims (6)

Mixture consisting of E-cyandiazohydroxide according to formula (I) and Z-cyandiazohydroxide according to formula (II), where formula (I) and (II) apply

A water-containing solution comprising a mixture according to Claim 1 . Process for the preparation of a mixture consisting of E-cyandiazohydroxide according to formula (I) and Z-cyandiazohydroxide according to formula (II), where for formula (I) and (II) applies

and wherein in a first process step 1 a component 1 comprising a) cyanamide, or b) chloroformamidine or a salt thereof, or c) a mixture of i) cyanamide and an acid, or ii) cyanamide and chloroformamidine, or iii) cyanamide and a Chlorformamidine salt, or iv) cyanamide, chlorformamidine and a chlorformamidine salt, and separately therefrom a component 2 comprising a nitrosating reagent are provided, and in a second process step 2 the provided component 1 and component 2 at a temperature in the range from -20 to + 10 ° C in water or in a water-containing reaction medium. Procedure according to Claim 3 , characterized in that the acid used in process step 1 is sulfuric acid, hydrochloric acid, formic acid or acetic acid. Method according to one of the aforementioned Claims 3 or 4th , characterized in that a reagent selected from the group consisting of sodium nitrite, potassium nitrite, butyl nitrite, pentyl nitrite and isopentyl nitrite is used as the nitrosation reagent. Use of a mixture according to Claim 1 or a solution thereof for the cyanation of aromatic carbocycles.

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