Self-consistent extended Hückel theory. II

Abstract

Using self‐consistent extended Hückel theory and the exsin approximation, equilibrium bond lengths are calculated for the C–H, N–H, O–H, C–C, C–N, C–O, C=C, C=O, C≡C, and C≡N bonds. The calculated single bond lengths are generally longer than experimental values, but the calculated multiple bond lengths are in good agreement with experimental values. The results for the equilibrium bond lengths show that the exsin approximation is superior to any previously used off diagonal approximation. Calculations on the two butanes and the two propanols indicate that the analysis of the results of an earlier article are correct and that self‐consistent extended Hückel theory coupled with the exsin approximation is as good CNDO for comparing stabilities of various isomers.