Max-Planck-instirut fiir Strahlenchemie. 0-4330 Mtilheim an der Ruhr, Germany (Received: December 28, 1990; In Final Form: February 26, 1991)(pNitropheny1) glyoxylic acid (NO2- PA) was studied by time-resolved and steady-state photochemical methods in water and mixtures with acetonitrile at room temperature. Irradiation of NO2-PA leads to pnitrosobenzoic acid (NO-BA) and C02 in substantial yield (@= 0.28 in aqueous solution ...