Argon Matrix Study of the Infrared Spectrum of Butatrienone

Abstract

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-1,3-dioxan-4,6- dione (4),2,2-dimethyl-5-(7?-oxabicyclo[2.2.1]hept-5?-en-2?-ylidene)- 1,3-dioxan-4,6-dione (5) and 3,4-diazatricyclo[5.2.1.0^2,6]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, 404w cm^-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 (1-¹³C) butatrienone.