VISIBLE LIGHT-INDUCED OXYGEN-TRANSFER FROM NITROGEN-DIOXIDE TO ETHYNEAND PROPYNE IN A CRYOGENIC MATRIX .1. IDENTIFICATION OF PRODUCTS

Photochemical reaction of ethyne.NO2 and propyne.NO2 pairs isolated in solid Ar has been observed at wavelengths as long as 582 nm (HC=CH.NO 2) and 615 nm(CH3C=CH.NO2). Continuous wave dye laser radiation was us ed to excite the reactants, and the chemistry was monitored by FT-infr ared spectroscopy. In the case of ethyne + NO2, the sole products were CH2=C=O and NO. The reaction of NO2 with propyne gave methylketene pl us a trapped intermediate, CH3C(=NO.)C(=O)H (formyl methyl iminoxy rad ical). Infrared spectra of this radical are reported for the first tim e. Product identification was based on D, O-18, and N-15 isotopic subs titution. Selective interconversion with tuned visible laser light rev ealed the presence of four conformers, most probably originating from isomerism about the C-C and the C=N bonds. Photoelimination of NO from the iminoxy radical was observed at wavelengths as long as 625 nm. Pr opynol and methylketene could be identified among the secondary photol ysis products.