The effect of d-functions on molecular orbital energies for hydrocarbons

Abstract Ab initio molecular orbital studies including d-functions in the basis set have been made on methane, acetylene, ethylene, ethane, propyne, allene, cyclopropene, propene and cyclopropane. It is shown that the strained cyclic molecules cyclopropene and cyclopropane are preferentially stabilized by the addition of d functions. If such functions are included, relative energies are given to an accuracy of 3 kcal/mole or better.