title: Photochemistry of Aryl Pentazoles: para-Methoxyphenylpentazole.
abstract: The photolysis of para-methoxyphenyl pentazole (MeOPP) in methylcyanide (MeCN), investigated in the far UV (FUV) and near UV (NUV) is compared with the photolysis of para-methoxyphenyl azide (MeOPA). The main photoproduct of MeOPP is MeOPA, which, due to further photon absorption, yields mostly 4,4'-dimethoxyazobenzene as the final thermally stable product. The overall product quantum yield of both MeOPP and MeOPA is about 0.5 due to competition with internal conversion (IC) to S0 implying ultrafast nonreactive processes. Both pentazole and azide yield only 4,4'-dimethoxyazobenzene (trans and cis isomers, trans first) upon FUV photolysis in dilute solutions, whereas in the NUV, though the azo isomers are still the major products, other species are also formed. The yields of these products are 17% and 10% for the azide and the pentazole, respectively. The difference in yield indicates pentazole photoreactions that do not proceed via the azide. The products observed upon NUV photolysis may be the precursors of tars commonly produced in azide photochemistry. The exclusive production of azo compounds in the FUV indicates a rapid route to the triplet nitrene, generally considered to be the precursor of azo products.
authors: Institute of Chemistry, The Hebrew University, Jerusalem 9190401, Israel.
authors: U
authors: U
authors: Geiger
authors: Institute of Chemistry, The Hebrew University, Jerusalem 9190401, Israel.
authors: Y
authors: Y
authors: Haas