A Theoretical Evaluation of Normal Frequencies of Vibration of the Isomeric Octanes

Abstract

A theoretical evaluation of some of the normal frequencies of vibration of the isomeric octanes has been made. This report gives the skeletal frequencies for those of the eighteen isomeric octanes which lead to representations having 7 or fewer frequencies. The forces are assumed to be valence forces. The force constants used are 4.12×10⁵ dynes per cm for the C–C bond stretching, and 0.37×10⁵ dynes per cm for the bending between two C–C bonds, the values being based on computations by the author for n‐propane, using the experimental data of E. F. Barker and Violet L. Wu. The angle between two C–C bonds was taken as 107° whenever possible. The results of this investigation are summarized by means of charts, showing the location of bands calculated. For the molecules reported all normal skeletal frequencies for a valence force model were evaluated, and attempts at correlation between experimental and theoretical bands have been made.