ABINITIO VIBRATIONAL ANALYSIS OF TRANS-2,3-DIMETHYLBUTA-1,3-DIENE AND GAUCHE-2,3-DIMETHYLBUTA-1,3-DIENE

The harmonic force fields of the s-trans(anti) and gauche conformers of 2,3-dimethylbuta-1,3-diene have been calculated ab initio at the RHF/6-31G//RHF/6-31G level. These force fields have been further refined using scale factors transferred from analogous calculations at the RHF/6-31G level for s-trans-buta-1,3-diene and ethane. A complete assignment of the experimental vibrational frequencies is given. Regularities in the vibrational spectra of the stable conformers of buta-1,3-diene, isoprene (2-methylbuta-1,3-diene) and 2,3-dimethylbuta-1,3-diene are discussed. © 1990.