I'EICIIICU aan. l, nH-l 2,414,056 UNITED STATES PATENT OFFICE 2,414,066 ISOMERIZATION Win?eld Scott, deceased, late of Akron, Ohio, by Ruth P. Scott, executrix, Akron, Ohio, assignor to Wingfoot Corporation, Akron, Ohio, a corpo ration of Delaware No Drawing. Application August 9, 1943, Serial No. 497,972 6 Claims. (Cl. 260-485) 1 2 This invention relates to the isomerization of alpha-beta unsaturated acids and esters from the cis to the trans form. The invention lies in the C——— S (5) CHa-CH use of a. conversion agent, without which no de tectable conversion occurs. The invention in % é —-S~CH2OH N Mcthylol-Z-mercapto-li-methylthiazole cludes the isomerization of such compounds in which one or more of the hydrogens connected (CH3)2N. C (S) S20 (S) .N ( CH3) 2 (6) directly to a carbon atom have been replaced Tetramethyl thiuram disul?de by chlorine, alkyl or other substituent. The ester may be an alkyl ester, such as methyl, ethyl, 10 (7) H propyl, etc., or an aralkyl ester, such as benzyl, etc. It includes the isomerization of angelic-acid esters to tiglic-acid esters; cinnamic esters from \/ S H the cis to the trans isomer; chlormaleic-acid esters to chlorfumaric-acid esters; citraconic 15 Piperidinium N,N-pentamethylene dithiocarbamic acid acid esters to mesaconic esters; crotonic-acid The invention will be illustrated by the follow esters from the cis to the trans isomer; etc. ing examples: /\N_C_S>N ‘ I l / k/ According to this invention, the isomerization Ezramplle 1 is effected in the presence of an isomerizing agent which contains the grouping A mixture of 15 grams of diethyl maleate and 0.3 gram of 2-mercapto-4-methylthiazole was heated in an oil bath at about 140° C. Every five minutes, a 0.4 ml. sample was withdrawn and s mixed with 0.6 ml. of Nujol. The consolute tem in which the linkage between C and S or C and perature of this mixture was determined, and N may be a single or double bond. Representa 25 from it, the percentage of diethyl fumarate in tive examples of such isomerizing agents, which the reaction mixture was calculated. The results include the thiazoles, thiazolines, thiuram disul are given below: ?des, etc., are: -—N—CI1—S’— (1) / 30 S Time Consolute Per cent ° 0. iumarate temp., diethyl C \N/ Just after mixing ________________________ __ 2-mercaptobenzothiazole 35 After heating to 140° 5 minutes at l40°__10 minutes at 140°“ 15 minutes at 140°.. ._ _ _ __._ 20 minutes at 140° _______________________ __ (2) 25 minutes at 140°“ S S Benzothiazyl disul?de (3) _ NM. 25 __________ .. 95.25 80.50 69. 25 58. 25 12 30 44 57 48. 25 70 41. 50 78 30 minutes at 140°__ 37. 00 83 35 minutes at 140° _______________________ _. 35. 25 85 Example 2 A mixture of 5 grams of monomethylmaleate and 0.1 gram of Z-mercaptothiazoline was heated at about 140° C. for one hour. The mixture dark 45 ened considerably during this time, but on cool ing, monomethyl fumarate crystallized out. Z-mercaptothiazoline (4) (l‘|J—-— S CHa-C 4J~SH % N 2-mercapto-4-methylthiazole Weight of product, 2.1 grams (42 per cent). Example 3 Two and a half grams of 2-mercapto-4-methyl 50 thiazole were dissolved in 85 grams of water, and 100 grams of maleic anhydride were added. The mixture was heated at its boiling point with stir ring for about 2.5 hours. Upon cooling, the solu 55 tion yielded 90 grams of fumaric acid. Further 3 4 heating for 4 hours and distilling o? most of the water resulted in the separation of an additional 22 grams of fumaric acid. Total yield, 95 per cent. The following table indicates the extent of the conversion, using different isomerizing agents at different temperatures, with the approximate time required for the conversion, and in several Example 4 Cl instances the results are compared with those obtained with known isomerizing agents: A mixture of 15 grams of diethyl maleate and Derivative converted Agent Th1???’ Helen?" 05%;???“ Maleic acid ____________ __ 2. 25 109-101 89 2.0 4. 0 2. 5 109-101 109-101 109-101 77 88 76 Monomethyl maleate. _ - _ 6. 5 1.0 109-101 140 42 Dimcthyl maleate . _ 2. 5 190 80 160 75 D Do _________________ __ _ _ __ 0. 5 1% iodine ___________ --__..--_ 1% Z-mercaptobenzothrazole_._ 1% 2-mercapto-4-methylthiazole _________ __ 95 1. 0 160 _ 1. 0 160 60 .__ 1.0 160 93 36 160 98 1% methylol-2-mercapto-4-methylthiazolc.__________________ __ 1.0 1% cyclohexylamine derivative of zinc thiofuroate. _ 0.5 160 16 1% tetramethyl thiuram disul?de _________________ __ _ 1.0 160 79 1% benzothiazyl disul?de ________ .1--. _______ ______.__ _ 1.0 160 13 1% piperdinium pentamethylene dlthlocarbamlc acid__ 1.0 160 41 1% Z-mcrcaptoquinoline ___________________________________ .. 1.0 160 (33 Other conversion agents include: Z-mercap 0.15 gram of 2-mercaptobenzothiazole was heated at about 160° C. for one hour. A determination 25 tothiazole, thiazyl disul?de, 4-methylthiazyl of the consolute temperature revealed that 60 per disul?de, tetraethyl thiuram disul?de, tetra =butyl thiuram disul?de, methYlol-Z-mercapto cent of the maleic ester had been converted to benzothiazole, methylol-2-mercaptothiazole, di the fumarate ester. Example 5 pentamethylene thiuram disul?de, diethyl am 30 monium diethyl dithiocarbamic acid, etc. A mixture of 5 grams of diethyl maleate and 0.025 gram (0.5 per cent) 2-mercapto-4-methyl thiazole was heated at about 120° C. for 80 min What is claimed is: 1. The process of isomerizing diethyl maleate to the diethyl fumarate which comprises the step of heating the maleate in the presence of 2-mer utes. Thirty-two per cent of the ester was con verted to the fumarate. 35 capto-4-methyl thiazole at Example 6 a temperature of about 140° .C. until conversion is substantially complete. Two grams of Z-mercaptobenzothiazole were 2. The process of isomerizing dialkyl maleates dissolved in 66.5 grams of water, and 118.5 grams which comprises heating the dialkyl maleate in of maleic acid were added. This mixture was 40 the presence of tetramethyl thiuram disul?de. heated at its boiling point with stirring for about 3. The process of isomerizing dialkyl maleates which comprises heating the dialkyl maleate in maric acid which separated was ?ltered off, dried, the presence of Z-mercapto-4-methyl thiazole. and weighed. Yield, 91.5 grams ('77 per cent) 4. The process of isomerizing diethyl maleate In determining the percentage of the trans 45 which comprises heating the compound in the form of an alpha beta unsaturated acid or ester presence of z-mercapto-ll-methyl thiazole. prepared in accordance with the process of this 5. The process of isomerizing dialkyl maleate invention, a mixture of Nujol (a special type of which comprises heating the dialkyl maleate in 2 hours. The solution was cooled, and the fu mineral oil) and a sample of the reaction mix ture resulting from the heating of the alpha beta 5 unsaturated acid or ester with any of the suit able isomerizing agents of this invention, is heated to about 120° C. (or some temperature higher than the consolute temperature of the mixture) and then the heated mixture is allowed to cool : and the temperature at which the mixture just begins to become clouded is observed and is re ferred to as the consolute temperature. This temperature is referred to a chart (on which is plotted a series of consolute temperatures and 60 corresponding conversion percentages obtained from known mixtures) and the corresponding percentage conversion obtained. the presence of a catalyst from the group con sisting of 2-mercaptobenzothiazole, 2~mercapto~ thiazoline, 2-mercapt0-4-methyl thiazole, meth ylol-Z-anercapto-ll-methyl-thiazole, tetramethyl thiuram disul?de, Z-mercaptothiazole, thiazyl disul?de, 4-methyl thiazyl disul?de, tetraethyl thiuram disul?de, methylol-2-mercaptothiazole, dipenta methylene thiuram disul?de and diethyl ammonium diethyl dithio carbamic acid. 6. The process of isomerizing a dialkyl maleate which comprises heating the dialkyl maleate in the presence of 2i-mercaptobenzothiazole. RUTH P. SCOTT, Emecutrz'a: of the Last Will and Testament of Win?eld Scott, Deceased.