Complete assignment of vibrational spectra of 1,5-cyclooctadiene—a theoretical and experimental infrared and Raman study

Abstract

The IR and Raman spectra of 1,5-cyclooctadiene (COD) have been carefully remeasured. The geometry, the harmonic force field, and IR and Raman intensities have been determined at the ab initio SCF level, using basis sets of split valence or higher quality. The Scaled Quantum Mechanical (SQM) force field method was used to predict the vibrational spectra which agree very well with experiment, enabling the definite assignment of all fundamentals. The good agreement between the theoretical and experimental spectra leaves little doubt that the free COD molecule possesses C2 symmetry in a twist-boat conformation. Based on the ab initio force field, the IR spectra of the perdeuterated and tetradeuterated molecules are predicted.