Raman and infra‐red spectra, normal coordinate analysis and conformation of 1,3‐cycloheptadiene

Abstract
The Raman and infrared spectra of liquid samples of 1,3‐cycloheptadiene have been studied in the range 3500–100 cm−1. Using a Valence Force Field previously obtained from other conjugated dienes, the vibrational frequencies of 1,3‐cycloheptadiene are calculated for a C2 and Cs conformation of the molecule which both have been proposed as reasonable structures from other spectroscopic evidence. By comparison it is concluded that normal coordinate calculation and vibrational spectra are consistent with a Cs conformation of the cycloheptadiene ring. On the basis of this the vibrational assignment of 1,3‐cycloheptadiene is given.