Studies of the reactions of the anhydrosulphites of α-hydroxy-carboxylic acids. Part V. Thermal decomposition of benzilic and mandelic acid anhydrosulphites

Abstract

An improved synthesis of phenyl-substituted anhydrosulphites has been achieved via the anhydrous copper(II) salts of benzilic and mandelic acids. The thermal decomposition of benzilic acid anhydrosulphite follows the pattern observed for simple unsubstituted, and alkyl-substituted anhydrosulphites, the principal products being sulphur dioxide and poly(benzilic acid). Mandelic acid anhydrosulphite shows quite different kinetic behaviour and undergoes an unexpectedly rapid fragmentation to yield benzaldehyde, carbon monoxide, and sulphur dioxide. The normal (thermal) ring-opening polymerisation reactions appears to take place in competition.