GB1056193A - The production of thiocarboxylic acid esters - Google Patents

Abstract

A thiocarboxylic acid ester is obtained by reacting an alcohol with a halocarboxylic acid, reacting the resulting ester of the halocarboxylic acid with an inorganic di- or polysulphide to form an organic ester di- or polysulphide and reducing the organic ester di- or polysulphide to form a thiocarboxylic acid ester. The esterification of the alcohol may be effected at a reflux temperature of 80-155 DEG C. for a period of 45-90 minutes by adding 1 mol of a halocarboxylic acid, the halogen preferably being chlorine or bromine, and 1 to 1.2 mol of alcohol to 0.005 to 0.05 mols of esterification catalyst, for example an acid such as hydrochloric, sulphuric or p-toluenesulphonic, or a base such as sodium or potassium hydroxide. A hydrocarbon solvent, for example toluene, xylene, heptane or cyclohexane may also be present. The organic ester polysulphide may be prepared by reacting the haloester prepared above with at least the equivalent amount of an inorganic di- or polysulphide, for example an alkali metal di- or polysulphide such as sodium or potassium di-, tri- or tetra-sulphides or an ammonium polysulphide, which is preferably dissolved in an aqueous medium, and the mixture heated to 20-100 DEG C. for 30-180 minutes. The organic polysulphide may be reduced to form the thiocarboxylic acid ester with nascent hydrogen, for example gaseous hydrogen in the presence of a hydrogenation catalyst such as Raney Nickel in a bomb or nascent hydrogen generated in situ by the reaction of an active metal, such as zinc, with an aqueous acid, such as hydrochloric, at a temperature between 10-100 DEG C. for 60-180 minutes. An example is given for the production of isooctyl thioglycollate.