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 acetonit rile with light of lambda>435 nm gives four main product categories. n amely, in dichloromethane at +20-degrees-C (relative yield, products): adducts 1 of hydroxy/trinitromethyl type (total 54%, see below), nitr o substitution products (total 8%, nitrobenzene, 1,3-dinitrobenzene an d 1,3,5-trinitrobenzene), trinitromethyl substitution products (26%, t rinitromethylbenzene, 1-nitro-4-trinitromethylbenzene, 1,3-dinitro-5-t rinitromethylbenzene) and phenols (total 12%, 2,4- and 2,6-dinitrophen ol, 2,4,6-trinitrophenol). In acetonitrile at + 20-degrees-C the same product groups comprised 15, 24, 39 and 18%, respectively, and, in add ition, a low yield (1.7%) of what is formally a cycloaddition product between 4-nitrobenzonitrile N-oxide and acetonitrile, 5-methyl-3-(4-ni trophenyl)-1,2,4-oxadiazole 2. The structure of 2 was determined by si ngle crystal X-rav analysis. The main adducts were assigned the struct ures of a cis/trans pair of 1-hydroxy-4-trinitromethylcyclohexa-2,5-di ene (NMR). Their formation in both dichloromethane and acetonitrile sh ows that adduct formation from photolysis of tetranitromethane/aromati cs is not only confined to polycyclic aromatics but can occur with a m aximally resonance-stabilized system, like benzene itself. The high co mplexity of the product mixture can be explained partly by elimination reactions of adducts, combined with further thermal and photochemical transformations.