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.