Valence-bond isomer chemistry. Part VI. Photochemical interconversion of perfluoro-1,3,5- and –1,2,4-trimethylbenzenes via para-bonded benzene and prismane isomers

Abstract

Upon u.v. irradiation in the vapour phase, perfluoro-1,3,5-trimethylbenzene is reversibly isomerized to perfluoro-1,2,4-trimethylbenzene, via the valence-bond isomers, perfluoro-1,3,5-trimethylbicyclo[2.2.0]hexa-2,5-diene, –1,3,5-trimethyltetracyclo[2.2.0.0^2,6,O^3,5]hexane, and -1,2,5-trimethylbicyclo[2.2.0]hexa-2,5-diene. The physical properties of the valence-bond isomers are discussed. Perfluoro-1,3,5-trimethylbicyclo[2.2.0]hexa-2,5-diene undergoes photochemical addition of 1 mol. equiv. of bromine, and substitution of an olefinic fluorine atom by methoxide.