VIBRATIONAL ANALYSIS OF A SERIES OF N-ALKYL CHLORIDES IN SOLID STATE - ETHYL CHLORIDE THROUGH N-HEXYL CHLORIDE

The infrared spectra of a series of n-alkyl chlorides, ethyl through n-hexyl, have been measured in the solid state at low temperature. Only two conformations of each molecule (for ethyl chloride only one) were found to be present. In both forms the carbons are coplanar. In one case (trans) the chloride is also in the plane and in the other (gauche) it is not. A nearly complete vibrational assignment for each form is given for the region 1500-290 cm-1. The analysis is based on normal coordinate calculations using force constants most of which were transferred from the n-paraffins. Twelve of the constants associated with the -CH2Cl group were adjusted until the average error between the calculated and observed frequencies of some 210 fundamentals reduced to 3.9 cm-1. These results support our recent interpretation of the vibrations of the extended n-paraffins. © 1969.