PHOTOCHEMISTRY AND ENVIRONMENT .13. PHOTOTRANSFORMATION OF 2-NITROPHENOL IN AQUEOUS-SOLUTION

The direct phototransformation of 2-nitrophenol is dependent on wavelength. The quantum yield is very low, but increases at short wavelengths (in a degassed solution at pH 8.2, phi-254 nm = 1.3 x 10(-3) and phi-365 nm = 2.2 x 10(-6)). The main photoproducts have been identified as catechol, cyclopentadiene carboxylic acids, 2-nitrosophenol, nitrohydroquinone, 3-nitrocatechol and 2-aminophenoxazone. In acidic solution, photohydrolysis into catechol and nitrous acid is the main primary photoreaction. Photoreduction into nitrosophenol and secondary hydroxylations into dihydroxynitrobenzenes are also observed. The latter reaction is attributed to the excitation of nitrous acid (or nitrite ions) formed by photohydrolysis. In basic solution, the ring photocontraction is the major primary reaction.