FR2707291A1 - Process for the preparation of an ester of an unsaturated carboxylic acid by a reaction catalysed by an organic tin compound - Google Patents

Abstract

Process for the preparation of an unsaturated carboxylic ester. It consists in carrying out the transesterification in the presence, as catalyst, of dibutyltin oxide. Chemical industry.

Description

Process for the preparation of an ester of an unsaturated carboxylic acid by a

  The present invention relates to processes for preparing unsaturated carboxylic acid esters at the α, β position by transesterification of a lower alkyl carboxylate with a higher alcohol. A process of this type is known from US-A-232,248. The catalysts are selected from titanium alkoxides. In U.S. 4,202,990, it is recommended to replace these catalysts with acetylacetonates, especially zirconium and calcium. It is also known from U.S. Patent 5037978 to use hafnium acetylacetonate to catalyze this transesterification reaction. The DE 1,932 patent. 625 also discloses a CH3-O-Na type catalyst for this reaction. The aim of the invention is to enlarge the range of catalysts which can be used for this reaction by catalysts less sensitive to hydrolysis than those of the art.

prior.

  The subject of the invention is a process for the preparation of an ester of an unsaturated carboxylic acid in position a, of formula:

H2C = C-C-O-CH2-CH2-S-R3 (III)

R1O

  R 1 being a hydrogen or methyl atom and R 3 being linear or branched alkyl having up to 14 carbon atoms, phenyl or phenylalkyl having up to 4 carbon atoms in its alkyl part, by reaction, in the presence of a catalyst of a light carboxylate of formula

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H2C-- C-C-O-R2 (I)

  Wherein R 1 is a linear alkyl radical having up to 4 carbon atoms, with an alcohol of formula

R3-S-CH2-CH2-OH (II)

  characterized in that the catalyst is an organic tin compound. This tin compound may especially be a dialkyl tin oxide having up to 8 carbon atoms in each alkyl part, a dialkyl dialkoxide of tin having up to 8 carbon atoms in each alkoxy or alkyl part, a dialkoxide of tin. tin having up to 8 carbon atoms in

each part having alkyloxy.

  The catalyst is advantageously the oxide of

dibutyl.

  It generally represents from 0.01 to 10% and preferably from 0.5 to 2% by mole of the alcohol. The light carboxylate (II) is generally in the range of 1.8 to 10 moles and preferably 2 to 4 moles per mole of alcohol. It is preferred that R2 be methyl. The process gives satisfactory results especially when R 1 is methyl and when R 3 has up to 14 carbon atoms and is

especially ethyl.

  The reaction is preferably carried out at a temperature of less than 130 ° C., and especially between 100 ° C. and 500 ° C. at a pressure of between 500 and 760 mm Hg (666.6 × 10 2 to 946 × 10 2 Pa) and preferably 600-700 mm. Hg

(800.102 to 1013.102 Pa).

  Since polymerizable substances are involved in the reaction, it is better to carry out the reaction without bubbling air in the presence of a polymerization inhibitor. There may be mentioned hydroquinone,

  the monomethyl ether of hydroquinone, the di-t-

  butylcatechol, phenothiazine, p-phenylenediamine and

methylene blue.

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  The reaction time usually varies between 1 and 6 hours. Once the reaction is complete, the target carboxylic acid ester can be recovered by distilling the mixture.

  reaction, especially under reduced pressure.

  The following example illustrates the invention. In a jacketed glass reactor of 500 ml capacity, provided with a variable speed mechanical center stirrer, a plunger rod for the introduction of air and an adiabatic distillation column with 10 rings packing of Raschig surmounted by an adiabatic distillation head is charged with 6.5 moles (650 g) of methyl methacrylate, 2.5 moles (265 g) of ethylthioethanol and 1.53 g (1900 ppm of the charge) of phenothiazine. . The catalyst is introduced in the amount indicated in the table. The pressure is adjusted to maintain a temperature equal to that given in the table. The draw of the methyl methacrylate / methanol azeotrope is controlled by a set temperature at the top (boiling temperature

of the +2 C azeotrope).

  The reaction is considered complete when the temperature at the top is equal to the boiling point of the methyl methacrylate under the pressure under consideration. A fraction consisting of methyl methacrylate and methyl alcohol is thus collected. The results obtained are

summarized in the table below.

  9'66 C ú'86L'8665'89Z '0 úg' OE LIT ETI 9 I'Z6 5'06 Z'8658'15 8'1tt89'0 L 9 'T IT 5 t1'966'68 S'C6L' O9 96'5u 9 'LT ILO 1I'66 | '86 ú'66Zt'99L9'ú 9'0 9' 9 'I út 96''69't6 ú5'69''9''9 9 IT 8' 86 96 S'L6 6L'08 '1T Z6'T 9' z 5'0 SgiI T% S%% grenakVEHO-Hja (H) HO-SIS (alou%) TX2euiTeSS S <D%) DdD (e) aplanG sAIeqeD o nselqel

2707291

  In this table, MAM stands for methyl methacrylate, ETE-OH stands for ethylthioethanol, (a) is the time for withdrawing the MAM-methanol azeotrope, GPC stands for gas chromatography, ETEMA is for ethylthioethyl methacrylate, C is the conversion of ETE-OH to percent by weight, C being equal to: (ETE-OH) remaining - (ETE-OH) introduced R is the weight yield in ETEMA, R being equal to: (ETEMA) formed x 100 (ETE-OH) introduced S is the weight percent selectivity, S being equal to

R

  These results show that dibutyltin oxide catalyzes the transesterification reaction and that the operating conditions of test 3 represent the best compromise for obtaining ETEMA with good yield and

good selectivity.

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Claims (7)

  A process for preparing an ester of an unsaturated carboxylic acid at position a, B of formula: H2C = C - C - O - CH2 - CH2 - S - R3   R 1 being hydrogen or methyl and R 3 being linear or branched alkyl having up to 14 carbon atoms, phenyl or phenylalkyl having up to 4 carbon atoms in its alkyl part, by reaction in the presence of a catalyst, a light carboxylate of formula H2C = C-C-O-R2 (I)   Wherein R 1 being a linear alkyl radical having up to 4 carbon atoms, with an alcohol of formula R3-S-CH2-CH2-OH (II)   characterized in that the catalyst is a compound organic tin.   2. Process according to claim 1, characterized in that the catalyst is a dialkyl tin oxide having up to 8 carbon atoms in each alkyl part, a dialkyldialkoxide of tin having up to 8 carbon atoms in each part alkoxy or alkyl, a dialkoxide of tin   having up to 8 carbon atoms in the alkoxy part.   3. Process according to claim 1, characterized   in that the catalyst is dibutyltin oxide.   4. Process according to any one of   Claims 1 to 3, characterized in that R1 is methyl, 7 2707291 R2 is methyl and R3 is ethyl.   5. Method according to one of claims 1 to 4,   characterized in that it consists in carrying out the reaction at   a temperature below 130 C.   6. Process according to any one of   preceding claims, characterized in that the   The catalyst represents from 0.01 to 10 mol% of the alcohol R30H.   7. Process according to any one of   preceding claims, characterized in that it consists   to carry out the reaction in the presence of a polymerization inhibitor.