CNDO Calculation of the Pseudorotational Potential Energy of Fluorocyclopentane

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Abstract
The potential energy for pseudorotation in fluorocyclopentane, C5H9F, has been calculated using the CNDO/2 approximate quantum‐mechanical method of Pople, Santry, and Segal. Calibration of the method for cyclopentane itself predicts an energy difference between the twisted and bent forms of less than 4 cm−1, in good agreement with experiment. For fluorocyclopentane energies calculated at different values of the phase angle φ are fit by a cosine‐barrier potential. Only the bent equatorial form is calculated to be stable, with a calculated barrier to pseudorotation of 356 cm−1. Frequencies of permitted transitions are calculated and found to be in good agreement with experiment.