Infrared Spectrum and Vibrational Assignment for Chlorine Monoxide, Cl2O

Infrared studies of chlorine monoxide (16O and 18O) in the region 200–4000 cm−1 for both gas and condensed phases are presented. The spectra require reassignment of the stretching fundamentals and reveal the previously unknown bending fundamental. The new assignment (solid phase: v1=630.7, v2=296.4, v3=670.8 cm−1) results in a new value for the Cl–O bond stretching force constant, Kr=2.75 mdyn/Å, which is strikingly lower than values previously cited. The bond in chlorine monoxide is proposed as the prototype Cl–O single bond. The low stretching-force constant indicates little ionic character in the Cl–O bond, in disagreement with conclusions based on nuclear quadrupole coupling data.