GB681711A - Improvements in or relating to the production of alkane disulphides and/or alkane thiols - Google Patents

Abstract

A process (a) for the production of an alkane disulphide and/or an alkane thiol comprises reacting an alkane disulphide with an alkane thiol having an alkyl group which is different from at least one of the alkyl groups of the alkane disulphide reacted therewith, whereby an intermolecular exchange of alkyl groups is effected and a process (b) for the production of an alkane disulphide comprises reacting an alkane disulphide with another alkane disulphide having at least one alkyl group different from both of the alkyl groups of the alkane disulphide reacted therewith, in the presence of an alkane thiol whereby an intermolecular exchange of alkyl groups is effected. If none of the products in process (a) are removed the proportions of unsymmetrical and new symmetrical disulphides formed will be determined by the equilibrium conditions of the system but if the alkane thiol formed is removed high yields of the new symmetrical disulphide will be produced in general in preference to the unsymmetrical disulphide. The alkane thiol formed may be removed by continuous fractionations during the reaction. In process (b) when reacting two different symmetrical alkane disulphides in the presence of an alkane thiol to give the unsymmetrical disulphide, the alkane thiol preferably has an alkyl group in common with an alkyl group of one of the disulphides reacted. In general either of the processes may be carried out in an aqueous or alcoholic medium, ethanol and an alkaline medium being preferred. The reaction may be carried out at room temperature but elevated temperatures are preferred, e.g. the reaction may be carried out at the boiling-point of the reaction mixture under reflux. The products are generally separated by fractional distillation. The process has application in the conversion of alkane thiols or disulphides to materials of different boiling point enabling their removal from other compounds of similar boiling point. In examples: (1) 3,4-dithiahexane, 2,2-dimethyl-3,4-dithiahexane (ethyl-tert.-butyl disulphide) and 2,2,5,5-tetramethyl-3,4-dithiahexane-(di-tert.-butyl disulphide) are produced by refluxing a solution of diethyl-disulphide and tert.-butyl mercaptan in aqueous ethyl alcohol containing potassium hydroxide, removing the ethane thiol as it is formed and fractionating the mixture of reaction products; (2) 6 - methyl - 3,4 - dithiaheptane (ethylisobutyl disulphide) is prepared by refluxing a solution of di-isobutyl disulphide, 3,4-dithiahexane and ethane thiol (ethyl mercaptan) in aqueous ethyl alcohol containing potassium hydroxide and isolating the desired product and residual starting materials.