Distortional effects on the ethane internal-rotation barrier

Abstract

The importance of vibrational deformations for the barrier to internal rotation in ethane is investigated. Simplified model calculations based on force constant data and empirical nonbonded potentials yield an eclipsed structure that is more open than the staggered form. It is found that the HCC angle is increased by a few tenths of a degree and the carbon-carbon bond is elongated by a few hundredths of an angstrom. Although these changes in geometry are small, their effect on the internal-rotation barrier may be significant.