GB410208A - Improvements in or relating to the production of unsaturated esters - Google Patents

Abstract

Lower alkyl esters of a -alkylacrylic acids are manufactured by reacting a lower alkyl ester of an a -hydroxy-a -alkylpropionic acid with phosphorus oxychloride. One molecular proportion of phosphorus oxychloride may be employed to every three molecular proportions of the hydroxy-ester, but larger yields are obtained by employing larger proportions of phosphorus oxychloride, e.g. about 1.5 molecular proportions to three of hydroxy-ester. The reaction is advantageously facilitated by warming the reaction mixture under reflux, e.g. to boiling or to 100 DEG C. Moisture is excluded from the reaction mixture, e.g. by means of a calcium chloride tube between the reflux condenser and the atmosphere, whilst the condenser is preferably provided with a spray arrester to catch any liquid carried away by the hydrogen chloride evolved. The reaction is preferably performed in the presence of a small quantity of an anti-polymerization material, e.g. hydroquinone, sulphur or copper, which should also be present during the purification of the product. The reaction mixture may be worked up by distillation, with or without reduction of pressure, which may be continued until the temperature of the liquid approaches 200 DEG C., the distillate being fractionated and the ester fraction purified by treatment with an alkali or alkali carbonate solution and then with water, followed by drying over anhydrous calcium chloride or sodium sulphate and redistillation under ordinary or reduced pressure. Examples describe the manufacture of methyl methacrylate from methyl a -hydroxyisobutyrate.