Studies of the reactions of anhydrosulphites of α-hydroxycarboxylic acids. Part VII. Polymerisation of anhydrosulphites derived from symmetrically substituted α-hydroxy-acids

Abstract

The ease of polymerisation of α-hydroxycarboxylic acid anhydrosulphites has been studied as a function of C-5 substituent size. Unlike other systems of this type, which polymerise less readily with increasing ring substitution the rate of polymerisation of anhydrosulphites increases as C-5 substituents methyl, ethyl, n-propyl, and n-butyl are successively introduced. The rate-determining process is the primary scission of the ring which takes place with sulphur dioxide elimination and concurrent ring contraction to form an α-lactone intermediate. This intermediate takes part in a rapid chain-propagation reaction which occurs spontaneously throughout the series. Although no variation in the rate of this reaction was detected, the polar character of the intermediate and its stability in other environments are affected.