Elimination and addition reactions. Part 40. The insignificant effect of strain in higher order eliminations in 1,1-bis(phenylsulphonyl) carbanions with ω-leaving groups

Abstract

Rates of cyclisation of 1,1-bis(phenysulphonyl) carbanions bearing distal leaving groups have been determined. The response of the system to solvent effects and to leaving group is similar to that in intermolecular nucleophilic substitution.

The system is very sensitive to the size of the ring formed; for iodides in ethanol the ratios for ring sizes 3 : 4 : 5 : 6 : 7 are 1 : 1.1 × 10^–5 : 1.0 × 10^–6 : 7.3 × 10^–10. The contribution of strain in the product to the enthalpy of activation is slight and inconsistent; the entropy of activation for cyclopropane formation is so favourable as to make this by far the most rapid process observed.