Conformational analysis and rotational barriers for different classes of molecules in terms of many atom exchange interactions

Abstract

Conformational analysis of simple molecules containing lone pair electrons such as H2O2, NH2OH, NH2NH2, is carried out as an extension of a recently proposed model where the barrier to internal rotation is assumed to arise only as a result of exchange interactions, calculated to first order using perturbation theory, among nonbonded atoms. Lone pair electrons associated to atoms located on the axis of rotation are effectively included in the model as additional nonbonded atoms. It is shown that exchange interactions among the nonbonded atoms of the extended cluster can be taken alone as responsible for the observed conformations and barriers. The model is then applied to molecules as propane and its derivatives, dimethylamine, dimethyl ether, with two consecutive axes of internal rotation and to the conformational analysis of polyoxymethylene. The results are in good agreement with experiments. The possibility of application to molecules of biological interest is discussed.