A THEORETICAL AND EXPERIMENTAL INVESTIGATION OF THE KINETICS OF RING-CLOSURE OF THE 3-METHYL-3-AZAHEX-5-ENYL RADICAL

Evaluation of the Arrhenius parameters for ring closure of the 3-methy l-3-azahex-5-enyl radical is reported. Cyclization of the radical is f ound to occur with high regioselectivity giving the exo-trig product e xclusively with an activation energy of 22 kJ mol(-1) and log A value of 11.1. The experimental activation barrier compares favourably with that determined by force field calculations which predict a value of 2 1 kJ mol(-1). The 3-methyl-3-azahex-5-enyl radical is therefore found to undergo ring closure some 70 times faster than the parent hex-5-eny l radical, in accord with predictions based upon geometrical considera tions.