Very low pressure pyrolysis of phenyl acetate

The kinetics of the unimolecular decomposition of phenyl acetate into phenol and ketene, reaction (1):\documentclass{article}\pagestyle{empty}\begin{document}$${\rm PhOCOCH}_3 \buildrel 1\over\rightarrow{\rm PhOH} + {\rm CH}_2 = {\rm C} = {\rm O}$$\end{document}has been studied under very low‐pressure conditions between 950 and 1120 K. In this range alternative processes such as the Fries rearrangement to o ‐hydroxyacetophenone or bond fission into phenoxyl and acetyl radicals are not observed. Based on present and previous evidence a novel four‐center transition state is proposed for reaction (1) which corresponds to the high‐pressure Arrhenius expression log ( k 1 , s −1 ) = 12.8 – 56.2/θ, θ = 4.575 × 10 −3 T kcal/mol.