Consistent force field calculation of conformations of spiro compounds

Abstract

Consistent force field calculations were made on a series of twelve spiro compounds of unusual topology, including four n-rotanes ( n = 3 to 6). The total intramolecular energy was minimized with potential energy functions which are sums of contributions from bond and angle deformations and from non-bonded interactions, with and without Coulombic terms. The predictive capability of this approach is witnessed by the generally good agreement of geometries arrived at under relaxation of all internal degrees of freedom with the few experimental structural data available on some of these compounds, and by comparison with predictions of other theoretical treatments. A procedure to express the angular strain at the spiro junctions in quantitative terms is proposed.