Approximate calculations on a protonation step in the reduction of propadienes

Abstract

The protonation of the radical anion produced as an intermediate by electron transfer to 1,3-dimethylpropadiene is studied by calculating the electrostatic molecular potential to which higher order perturbation terms are added (induction energy). The preferred protonation site is at the central carbon atom, producing a planar allyl radical, in agreement with experimental evidence. A different conclusion is reached if the induction energy is neglected.