PHOTOCHEMICAL BEHAVIOR OF 4-NITROSOPHENOL IN AQUEOUS-SOLUTION

In acidic medium (pH approximate to 1)4-nitrosophenol irradiated in th e range 296-366 nm is mainly transformed into benzoquinone (75-80%). T he quantum yield of this reaction is wavelength dependent: it is about 6 times higher at 365 nm than at lambda less than or equal to 313 nm. This phenomenon is attributed to an equilibrium between two tautomeri c forms, nitroso and quinone monooxime, the former being much more pho toreactive than the latter. In unbuffered aqueous solution (pH = 5-6) the formation of an intermediate is observed. Its HPLC retention time is just a little shorter than that of benzoquinone and the maximum of its absorption band is located at 235 nm. The rate of transformation o f this intermediate increases with decreasing pH.