The Study On The Structures And Photochemistry Of Nitropyridines

The photoreactions of four o-nitroalkoxypyridine derivatives,3-benzyloxy-2-nitropyridine (BzONP), 3-ethoxy-2-nitropyridine (EtONP),3-methoxy-2-nitropyridine (MeONP), 2-benzyloxy-3-nitropyridine (BzONP'), and2-benzyloxypyridine (BzOP) in methanol and isopropyl alcohol irradiated by HPML(High Pressure Mercury Lamp) were studied. The photoproducts were separated andidentified. The proceedings of the photoreactions were traced by GC-MS. Theformation mechanism of primary photoproduct benzaldehyde was proposed, whichwas through the six-membered rings intermediate. The "Parallel Experiment" ofbenzaldehyde under thermic and photic condition not only proved that thebenzaldehyde dimethylacetal was not yielded through thermic proceeding, but alsosuggested that it was not obtained through the photic proceeding of benzaldehydealone. So the formation mechanism of acetal through the photocatalysis ofnitropyridine derivatives was proposed, which can also explain why BzONP'performs another route in isopropyl alcohol.In addition, the photoproperties of nitrobenzene in p-xylene under differentwavelength UV were also studied. The photoproducts were identified, and themechanisms of reaction were proposed.Moreover, the molecular structures of BzONP and BzONP' were investigatedthrough X-ray single crystal diffraction and theoretical calculation. The twist of nitrogroup out of the pyridine ring by a large angle was explained by the calculation withDFT and HF methods. The rotation barrier of nitro group was calculated, which cantestify their disordered state under room temperature. IR and Roman spectra ofBzONP were also predicted with DFT and HF methods, which coincided with theexperimental value well.