Studies of the reactions of anhydrosulphites of α-hydroxycarboxylic acids. Part VIII. Polymerisation of anhydrosulphites of α-hydroxycycloalkanecarboxylic acids

Abstract

The anhydrosulphites of α-hydroxy-cyclobutane-, -cyclopentane-, -cyclohexane-, and -cycloheptane-carboxylic acids have been prepared in order to examine the effect of ring strain on polymerisation rates. Of this series only the spirocyclobutane derivative was not obtainable substantially pure. This compound is also abnormal in that the major product of thermal decomposition in non-hydroxylic solvents is glycollide rather than the expected poly-α-ester. The less strained spirocyclopentane and spirocyclohexane derivatives eliminate sulphur dioxide smmoothyl by a first-order process in the well-established manner of the open-chain analogues. The effect of increased ring strain in α-hydroxycycloheptanecarboxylic acid is reflected in its greater rate of thermal decomposition. The relative magnitudes of the kinetic parameters are discussed and the tendency of the anhydrosulphites to undergo direct bimolecular reaction with attacking hydroxylic species assessed. Although the spiro-cyclopentane, -cyclo-hexane, and -cycloheptane derivatives yield the appropriate poly-α-esters, these, in contrast to the symmetrical open-chain analogues, are non crystalline.