DE1912730A1 - Process for the preparation of alpha-oxicarboxylic acid esters - Google Patents

Description

Badisohe aniline- 3c Soda-Fabrik AG

Our reference: O.Z. 26 064 WB / IB 6700 Ludwigshafen, March 11, 1969

Process for the production of ÄC-oxicarboxylic acid esters

The invention relates to a process for the production of Qi-oxicarboxylic acid esters by reacting oC-oxicarboxylic acids with alcohols with the addition of water and in the presence of acidic ion exchangers.

It is known that esters can be prepared by reacting alcohols with carboxylic acids (Houben-Weyl, Methods of Organic Chemistry, Volume 8, pages 516 ff.). The catalysts used are mineral acids or organic sulfonic acids, e.g. B. p-toluenesulfonic acid is used. It is also known that the esterification between alcohol and carboxylic acid can be carried out in the presence of an acidic ion exchanger (Houben-Weyl, Methods of Organic Chemistry, Volume I, 1, page 587). In order to make the esterification as quantitative as possible, it was proposed to remove the water that forms from the equilibrium. So was z. B. for the esterification of ot-oxicarboxylic acids dehydrated copper sulfate described as a particularly suitable catalyst (loc. Cit., Volume 8, page 519). So far, no ion exchangers have been used for the esterification of dC-oxicarboxylic acids, but hydrogen chloride and mineral acids have been used as catalysts (Recueil des Travaux Chimiques des Pays-Bas, Volume 68, page 618 (19 ^ 9); Industrial and Engineering Chemistry, Volume 38, pages 229 ff. (19 ^ 6)).

It has now been found that o £ -oxicarboxylic acid esters are advantageously obtained by reacting oC-oxycarboxylic acids with alcohols in the presence of acidic catalysts if the reaction is carried out in the presence of acidic ion exchangers and with the addition of water.

Compared to the known methods, the method delivers the invention in a simple and economical way a large number of oC-oxicarboxylic acid esters in better yield and purity. the

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The use of ion exchangers facilitates the separation of the end products and the catalyst, avoids corrosion problems and Catalyst losses and thus increases the economic efficiency of the process. It is also in view of the state of the art Surprisingly, the addition of water permits higher yields and does not significantly promote side reactions.

Preferred starting materials are cC-oxicarboxylic acids of general formula

OH 0

! It

R ₁ -CC-OH I

in the FL an alkyl radical with 1 to 6 carbon atoms, a cycloalkyl radical with 5 to 7 carbon atoms, an aralkyl radical with 7 to 12 carbon atoms, an aryl radical having 6 to 10 carbon atoms or a hydrogen atom. The remnants mentioned can nor by inert groups and / or atoms under the reaction conditions - z. B. hydroxyl groups, nitro groups, may be substituted.

It can e.g. B. The following CC Oxicarbonsäuren be used as starting materials I: lactic acid, glycolic acid, glyceric _s FLC Hydroxyot-cyclohexy acid, o6-HydVoxy-dihydrocinnamic, o £ -Hydroxyphenylessigsäure!.

The of-oxicarboxylic acids are with alcohols, z. B. aromatic, cycloaliphatic, araliphatic or, in particular, aliphatic alcohols, reacted in a stoichiometric amount or with an excess of alcohol, preferably up to a 5-fold excess of alcohol over the stoichiometric amount. If the Q ^ -oxicarboxylic acid has more than one <^ - oxicarboxylic acid residue, a »B-. the tartaric acid, and if at least 1 mole of alcohol is used per C-oxicarboxylic acid residue, the corresponding oi-oxicarboxylic acid polyester is obtained, e.g. B. the tartaric acid diesters. Accordingly, you need in the implementation of polyalcohols, for. B. ethylene glycol _s with

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οί-oxicarboxylic acid in each case at least 1 mol of oi-oxicarboxylic acid per hydroxyl group for the preparation of the corresponding poly ot-oxicarboxylic acid ester, ζ. B. the ethylene glycol di-ot-oxicarboxylic acid ester. Preferred alcohols are those of the general formula

R ₂ OH I,

in the R "is an alkyl radical with 1 to. 6 carbon atoms, one Cycloalkyl radical with 5 to 7 carbon atoms, an aralkyl radical with 7 to 12 carbon atoms or a phenyl radical, the radicals mentioned being replaced by the inert ones listed above Groups and / or atoms can be substituted.

It can e.g. B. the following alcohols are used as starting materials: methanol, tert-butanol, isopropanol, cyclohexanol, benzyl alcohol, Phenol, glycerine, propylene glycol, n-butanol.

The reaction is carried out with the addition of water, generally in an amount from 1 to 50% by weight , preferably from 8 to 50% by weight, based on 06-oxicarboxylic acid. The water can be used in any way, e.g. B. in a mixture with the alcohol or the oC-oxicarboxylic acid or as a separate additive, fed to the reaction. Thus, o ^ -oxicarboxylic acids with a water content derived from their preparation can also advantageously be used. This added amount of water does not include the amount of water of reaction which is only formed in the reaction mixture as a result of the esterification.

The reaction is carried out in the presence of acidic ion exchangers, preferably acidic synthetic resin exchangers. Such exchangers are z. B. all in Houben-Weyl, Methods of Organic Chemistry, Volume I / l, page 528, Table 3 described cation exchangers. Strongly and moderately acidic exchangers are preferably used, ζ. B. phenolic or polystyrene sulfonic acid resins, or corresponding acidic resin-containing exchangers, ζ. B. bifunctional Condensation resins. The amount of starting materials used or the exchanger depends on the selectivity or the number of active exchange groups of the exchangers used in the reaction

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tion temperature, in general, from 20 to 25 wt.% exchanger, based on Λ-oxycarboxylic acid, in batch operation and continuous operation 50 to 400 wt.%, preferably 200 to 300 Gew./? Exchanger, based on the average amount of o6-oxicarboxylic acid passed through the exchanger per hour. The amount of water contained in the dry exchangers, which may be, depending on the structure up to 50 wt.% Is not included in the above-defined addition of water. The shape and grain size of the exchanger can be chosen arbitrarily within a wide range. With regard to the manufacture and details of the use of ion exchangers, reference is made to the chapter "Ion exchangers" of the work mentioned.

The reaction is generally carried out at a temperature between 20 to 150 ^° C., preferably between 60 to 100 ^° C., without pressure or under pressure, continuously or batchwise. In general, the components of the reaction mixture, for example the alcohol, serve at the same time as solvents; organic solvents which are inert under the reaction conditions, e.g. B. acetone, tetrahydrofuran, dioxane, use «

The reaction can be carried out as follows: A mixture of ok-oxicarboxylic acid, alcohol and water, optionally together with an organic solvent, is continuously at the reaction temperature passed through a column reactor filled with the exchanger. The aforementioned mixture can be used accordingly hold together with the exchanger also discontinuously for 120 to ISO minutes at the reaction temperature * From the continuous Discharge or the reaction mixture of the discontinuous The end product is converted in the usual way, for example by fractional distillation, isolated.

The compounds which can be prepared by the process of the invention are solvents, fragrances, plasticizers and valuable starting materials for the production of such substances and of plastics Detergents and dyes. Regarding the use is on Ulimanns Encyclopedia of Industrial Chemistry, Volume 5 »Pages 108 ff and Volume 13, pages 73 ff.

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The parts given in the following examples are parts by weight.

example 1

A heated to 80 ⁰ C, cylindrical reactor with 1000 parts of a Polystyrolsulfonsäureharzes, which is available under the name ^ LE-WATIT S 100 commercially filled. 500 parts of lactic acid, 355 parts of methanol and 70 parts of water are passed through the reactor at 80 ° C. for 60 minutes. The liquid discharge, which consists of methanol, water, lactic acid methyl ester and lactic acid, is broken down into its components by distillation. This gives 474 parts Milchsäuremethylester (82% of theory, based on the lactic acid), bp. 58 _g ⁰ C.

For comparison, the reaction is carried out under the same conditions, but instead of adding water and using the exchanger with the addition of a) 10 parts of p-toluenesulfonic acid and b) 10 parts of concentrated sulfuric acid. Appropriate work-up gives a) 270 parts (46.7 % of theory) or b) 283 parts (49 % of theory) of methyl lactate.

Example 2 ■,

The reaction is carried out as in Example 1. Instead of ® LEWATIT S 100 ® BERMUTIT RS is used. Parts of lactic acid methyl ester are obtained (80 % of theory, based on the lactic acid used).

Example 3

Due to the moist with 150- parts ® LEWATIT S 100 (corresponds to about 75 parts LEWATIT S 100 dry) coated and heated at 8O ⁰ C reactor is a mixture for 8 hours, consisting of 270 parts of lactic acid, 372 parts of ethylene glycol and 90 parts of water , directed. The acid number in the starting solution and in the discharge is 36.

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After distillation of the discharge, which consists of ethylene glycol, water, lactic acid [2-hydroxy-ethyl ester] and lactic acid, 298 parts of lactic acid-jj> -hydroxy-ethyl ester] (74 % of theory, based on lactic acid used) are obtained from Kp ₁₀ 140 C.

Example 4 "

The reactor described in Example 1 and filled with LEWATIT S 100 is charged with a mixture of 1,200 parts of glycolic acid, 4,800 parts of methanol and 400 parts of water continuously at 80 ^° C. for 8 hours. The acid number, which is 138.5 in the starting solution, has fallen to 40 in the discharge.

After distillation of the liquid discharge consisting of methanol, water, glycolic acid and glycolic acid methyl ester, 1,018 parts of glycolic acid methyl ester (71.7 % of theory, based on the glycolic acid used) with a boiling point of ₂₀ 58 ^° C. are obtained.

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Claims (1)

O.Z. 26 064 Patent entitlement A process for preparing .alpha.-Oxic-arbonsäureestern by reacting o £ -Oxicarbonsäuren with alcohols in the presence of acid catalysts characterized in that the ₃ reaction is carried out in the presence of acidic ion exchangers and with the addition of water. Badische Anilin- & Soda-Fabrik AG © 09840/2161