The calculation of force constants and normal co-ordinates—VII Normal co-ordinates in the E species of allene

Abstract

Force constant and normal co-ordinate calculations are reported for the E species vibrations of the allene molecule. Data on the fundamental vibration frequencies of allene- h 4, allene- d 4 and allene-1.1- d 2 and on the five experimentally determined Coriolis zeta constants of C 3H 4 and C 3D 4, were used in a force constant refinement procedure. Allowing for product and sum rules this gives 21 independent data which were used to refine to the most general harmonic force field (10 parameters) with one constraint (in the absence of any constraints the refinement was not satisfactory). The results have been used to calculate the complete ζ z Coriolis interaction matrix for the allene-1.1- d 2 molecule, and hence to calculate the expected rotational structure of the perpendicular bending vibrations of this molecule; the good agreement obtained with the observed spectra is a check on our results.