Steric Effects. II. General Equations. Application to Cis- and Trans−2-Butene

Steric energy and the semi-empirical method of calculating steric energy are discussed in the language of potential surfaces. Equations are given relating ΔH00 for several types of reactions commonly used to exhibit steric effects experimentally to the steric energy of the molecules involved in the reactions. The equations of Westheimer and Mayer for the calculation of the steric energy of a molecule are generalized in several respects. The difference in ΔH00 (formation) between cis and trans−2-butene is calculated as a steric effect. Because of various complications the application of the method in its present form to molecules such as H2O, NH3, PF3, etc., is rather unsatisfactory.