Ground state normal vibrations and force field of ethynylbenzene

Abstract

An accurate intramolecular force field for ethynylbenzene and its three deuterated isomers is determined from experimentally observed vibrational frequencies. Vibrational assignments are discussed in the light of the calculated potential energy distribution. Mode ν15 of a2 symmetry is assigned at 655 and 657 cm-1 in C6D5CCH and C6D5CCD, respectively. The vibrational frequency of 162 cm-1 is given double assignment as ν24 and ν36. Harmonic mode scrambling is observed in ν27, ν29, ν30 and ν31 in going from the parent molecule to the one with ring deuteration. © 1995.