Infrared Spectrum and Vibrational Potential Function of Ketene and the Deuterated Ketenes

Abstract

Infrared spectra of solid ketene and ketene in argon reveal a new fundamental at lower frequency (CH2CO, 438 cm—1; CD2CO, 371 cm—1; CHDCO, 398 cm—1) than any previously reported. These spectra and additional gas-phase spectra provide a basis for a reassignment of the vibrational spectrum. The vibrational potential function, centrifugal distortion constants, Coriolis coupling constants, and thermodynamic properties of ketene have been calculated. The out-of-plane hydrogen bending force constant is found to be surprisingly low, about one-third of that for ethylene. In addition, the analysis of the rotational structure of several perpendicular bands yields improved estimates of the A moment of inertia and hence of the HCH angle (122.3°) and the C–H bond length (1.079 Å) of ketene.