Studies of the reactions of anhydrosulphites of α-hydroxy acids, part IX. thermal polymerisation of anhydrosulphites of α-hydroxy α-methyl carboxylic acids

Abstract

The anhydrosulphites of a series of unsymmetrically substituted α-hydroxy acids have been prepared and their susceptibility to polymerisation by thermal decomposition studied. The first order rate determining ring scission process, leading to the formation of a reactive α-lactone intermediate which then undergoes spontaneous polymerisation, is the predominant mechanism even with substituents up to C8. As the length of the n-alkyl substituent is increased the rate of decomposition and thus polymerisation increases until a plateau value is reached at around C3. Further increase in substituent length decreases the rate of decomposition, an effect which is attributed to steric hindrance of the leaving group by long (C6—C8) substituents.