PHOTOCHEMICAL NITRATION BY TETRANITROMETHANE .15. FORMATION OF ADDUCTS AND THEIR SECONDARY PRODUCTS IN THE PHOTOCHEMICAL-REACTION BETWEEN BENZENE AND TETRANITROMETHANE

Photolysis of benzene/tetranitromethane in dichloromethane or acetonitrile with light of lambda>435 nm gives four main product categories. namely, in dichloromethane at +20-degrees-C (relative yield, products): adducts 1 of hydroxy/trinitromethyl type (total 54%, see below), nitro substitution products (total 8%, nitrobenzene, 1,3-dinitrobenzene and 1,3,5-trinitrobenzene), trinitromethyl substitution products (26%, trinitromethylbenzene, 1-nitro-4-trinitromethylbenzene, 1,3-dinitro-5-trinitromethylbenzene) and phenols (total 12%, 2,4- and 2,6-dinitrophenol, 2,4,6-trinitrophenol). In acetonitrile at + 20-degrees-C the same product groups comprised 15, 24, 39 and 18%, respectively, and, in addition, a low yield (1.7%) of what is formally a cycloaddition product between 4-nitrobenzonitrile N-oxide and acetonitrile, 5-methyl-3-(4-nitrophenyl)-1,2,4-oxadiazole 2. The structure of 2 was determined by single crystal X-rav analysis. The main adducts were assigned the structures of a cis/trans pair of 1-hydroxy-4-trinitromethylcyclohexa-2,5-diene (NMR). Their formation in both dichloromethane and acetonitrile shows that adduct formation from photolysis of tetranitromethane/aromatics is not only confined to polycyclic aromatics but can occur with a maximally resonance-stabilized system, like benzene itself. The high complexity of the product mixture can be explained partly by elimination reactions of adducts, combined with further thermal and photochemical transformations.