ARGON MATRIX STUDY OF THE INFRARED-SPECTRUM OF BUTATRIENONE

Butatrienone, H2C=C=C=C=O, was generated by pyrolysis of each of six different precursors in a stream of argon at temperatures in the range 710-880°C, and the pyrolysate- argon mixture was condensed on a Csl plate at c. 10 K. Infrared spectra were obtained between 4000 and 250 cm-1. Two precursors, buta-2, 3-dienoic trifluoracetic anhydride (1) and buta-2, 3-dienoyl chloride (2), gave pyrolysates showing a spectrum consisting of six strong bands and five weak bands. Four precursors, bicyclo[2.2.1]hept-5′-en-2′-ylideneacetic trifluoracetic anhydride (3), 5-(bicyclo[2.2.1]hept-5′-en-2′-ylidene)-2, 2-dimethyl-l, 3-dioxan-4, 6- dione (4), 2, 2-dimethyl-5-(7′-oxabicyclo[2.2.1]hept-5′-en-2′-ylidene)-l, 3-dioxan-4, 6-dione (5) and 3, 4-diazatricyclo[5.2.1.02, 6]deca-3, 8-diene-endo-cis-2, 6-dicarboxylic anhydride (6) gave pyrolysates showing spectra consisting principally of the six strong bands. The observed bands assigned to matrix-isolated butatrienone were at 3105w, 3035s, 3010w, 2964w, 2242s, 1996w, 1495s, 1456s, 728s, 404wcm-1. Calculated frequencies, using various models, for butatrienone are reported and are used to make plausible assignments. The strongest band (V2) attributed to butatrienone was at 2242 cm-1 which was shifted to 2200 cm-1 in (l-13C)butatrienone. © 1990 ASEG.