VIBRATIONAL AND CONFORMATIONAL-ANALYSES OF A SERIES OF BRANCHED OCTANES .2. 2,2-DIMETHYLHEXANE AND 2,5-DIMETHYLHEXANE

In previous spectroscopic work on dimethylhexanes, complete vibrationa l assignments of each isomer in its most stable conformation were made with the aid of normal-coordinate analyses. In this communication, th e vibrational spectra of 2,2- and 2,5-dimethylhexane are re-examined, and a number of bands are assigned to less stable conformers whose str uctures are determined by molecular mechanics calculations. The measur ed relative integrated intensities of several pairs of bands as a func tion of temperature yields values for the enthalpy differences between conformers.