Ionic interactions. Part 3.—Semi-empirical studies of the pyrazine-lithium ion-pair

Abstract

The CNDO/2 method has been applied to the monoprotonated pyrazine radical. The proton is placed in the region of the nitrogen lone-pair electrons in agreement with a previous calculation using the extended Hückel method. Both methods have been used to calculate the most probable structure of the pyrazine-lithium ion-pair, and both methods predict that the lithium atom is placed above the centre of the pyrazine ring. Some attempts are made to incorporate possible effects due to solvation but this does not alter the conclusions. These results do not explain the electron spin resonance spectrum of the pyrazine-lithium ion-pair.