Calculation of the Barrier to Internal Rotation in Ethane

Wavefunctions and energies for both the eclipsed and staggered forms of ethane have been calculated in the limited basis set, self-consistent-field approximation. The basis functions are a minimum set of Slater orbitals. All integrals have been evaluated to the necessary accuracy. The calculated value of the barrier to internal rotation is 3.3 kcal/mole in good agreement with experiment. The sensitivity of the value to improvements in the wavefunctions cannot be estimated readily. The bearing of this calculation on proposals of the origin of the barrier is discussed. A transformation to localized molecular orbitals will be necessary for a more detailed discussion of the barrier.