INFRARED SPECTRA OF THE ACETYL AND VINOXY FREE RADICALS TRAPPED IN SOLID ARGON

When F atoms produced in a microwave discharge through a sample of $NF_{3}$ in argon carrier gas react with acetaldehyde, also mixed with a large excess of argon, and the products are frozen onto a cryogenic surface maintained at 14 K, a rich infrared spectrum results. One group of absorptions, destroyed by exposure of the sample to the visible component of the Nernst glower background, has been assigned to the acetyl $(CH_{3}CO)$ radical and to the complex of this radical with HF, Another group of absorptions which disappear on photolysis of the sample by radiation of wavelength shorter than 290 nm and which also appear in similar studies of the $F + C_{2}H_{4}O$ reaction can be assigned to the vinoxy $(CH_{2}CHO)$ free radical and its HF complex. Detailed isotopic substitution experiments support these identifications, provide information on the vibrational assignments, and demonstrate that the vinoxy radical possesses the formyl methyl $(CH_{2}-CH=O)$ structure in its ground electronic state