Molecular mechanics calculations on alkanes and non-conjugated alkenes

Abstract

A new force field has been developed for the calculation of geometric and thermodynamic properties of alkanes and non-conjugated alkenes. The force field is a significant improvement on those of its kind in current usage and reproduces the heats of formation and hydrogenation of 60 diverse alkanes and alkenes with an avarage absolute difference of 0.55 kcal mol^–1 between observed and calculated enthalpies. The corresponding figures for geometric properties are 0.009 Å. 0.6° and 0.9°. in bond lengths, bond angles, and torsion angles, respectively over a set of 93 observations. Particular attention has been paid to the structural and thermodynamic properties of molecules which are not adequately reproduced by previous force fields.