DIOXIRANE VIBRATIONAL FREQUENCIES - AN UNSETTLING RELATIONSHIP BETWEEN THEORY AND EXPERIMENT

There appears to be a conflict between theory and experiment concernin g the vibrational frequencies of dioxirane, a CH2O2 isomer. Here we em ploy sophisticated ab initio quantum mechanical methods with large bas is sets to determine geometry, harmonic vibrational frequencies, infra red (IR) intensities and isotopic shifts of dioxirane. At the highest level of theory, the CCSD(T) approach is used together with a cc-VTZ2P + f,d basis set. Best predictions for CO asymmetric and OO stretching (or OCO deformation) harmonic frequencies are 931 (b(2)) cm(-1) and 7 59 (a(1)) cm(-1), respectively. The IR intensities of these two peaks are predicted to be 19 km mol(-1) and 1 km mol(-1). An examination of the experimental vibrational frequencies of substituted dioxiranes is also presented. Calculated frequencies, intensities, and isotopic shif ts all imply that the two experimental IR features (with their observe d intensity ratio of 2.8) assigned to CO stretching (839.0 cm(-1)) and OCO deformation (800.9 cm(-1)) frequencies by J. R. Sodeau and L. J. Whyte (1991, J. chem. Soc. Farnday Trans., 87, 3725) should be re-addr essed.