Attractive Nonbonded Interactions in 1-Substituted Propenes. Consequences for Geometric and Conformational Isomerism

Heteroatoms at the 1 position of propene can interact with the methylene group through space and through the olefinic bond. This interaction can be attractive in nature and responsible for both the lower energy of the cis isomer relative to the trans isomer and also the lower rotational barrier of the cis isomer relative to the rotational barrier of the trans isomer. The proposed model is tested by SCF-MO semiempirical calculations and the qualitative generalizations are found to be in good accord with the observed experimental trends.