Simple Model of Short-Range Interactions. III. Ethane, Propane, and Butane

Abstract

With a Hückel-type Hamiltonian it can be shown that in a molecule described by a one-determinant wavefunction of localized nonorthogonal bond orbitals the intramolecular interaction energy turns out to be additive between pairs of different bonds to second order in the intergroup overlap. The possibility of building up the conformational energy of a molecule simply by adding contributions from all pairwise interactions between vicinal bonds has been examined for ethane, propane, and butane. The numerical results obtained within a crude first approximation to the matrix elements of the energy operator are highly encouraging.