Matrix isolation study of the vacuum ultraviolet photolysis of methyl cyanide Vibrational and electronic spectra of the CNC free radical
Visible-ultraviolet spectra of CH 3CN deposited in an argon matrix at 14 K with concurrent 1216-Å photolysis show prominent absorptions of CN and CNC and weak absorptions of CCN. The far infrared spectra of deposits made using similar experimental conditions show a peak at 134 cm -1 which has tentatively been assigned to the lowest frequency component of the bending fundamental of ground-state CNC, split by strong Renner-Teller interaction. Detailed isotopic substitution studies have confirmed the assignment of a prominent absorption at 1453 cm -1 and of its satellite at 1461 cm -1 to the previously unidentified antisymmetric stretching fundamental, ν3, of CNC. The stretching force constant for this molecule is estimated to lie between 8.0 and 8.5 × 10 2 N · m -1 and the stretching-interaction force constant between +2.5 and +3.0 × 10 2 N · m -1. Consideration of the photoprocesses important in these experiments suggests that CNC is formed primarily by photodissociation of CCN and cage recombination of the resulting C + CN.