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Laser flash and steady irradiation studies have been carried out on the 4-carboxybenzophenone (CB)-4-carboxybenzhydrol (CBH2) and CB-hydrazine systems over the pH range 5.8-12. In reaction with CBH2, CB triplet is quenched in part by the carboxylate, Aq 4 x 106 M"1 s"1; total reaction, A4 = 3.0 X 107 M"1 s"1, leads to the ketyl radical CBH•, = 1.7. Absorption spectra were recorded for CB triplet, Xma, = 535 nm (e = 6600 M"1 cm"1), for CBH•, Xmal = 570 nm (e = 5500), and for the radical anion CB"•, X^, = 660 nm (e = 8100). The pAa of CBH• was determined, 8.2. Rate constants were determined: for combination of CBH• to pinacol, 2 k6 = 1.8 X 109 M"1 s'1; for reactions of CBH• with CB", k1 = 1.1X 109 M'1 s'1; for disproportionation of 2CB"•, 2Ag = 9.8 X 106 M"1 s"1. Factors to convert observed yields of photoreduction by hydrazine to yields of ketyl radical leading to pinacol and hydrol were determined from effects of pH on quantum yields of reduction of CB by CBH2. Reduction of CB triplet by neutral hydrazine occurs with kir = 6.8 X 108 M"1 s"1, forming ketyl radical with = 1.0, measured relative to the CBH2 reaction. The reaction with protonated hydrazine is slower, k'ir = 4.4 X 106 M"1 s"1. Computer simulation, using the measured rate constants, pKa and primary yields, and literature constants

Communications to the Editor 1419 product sublimed into a trap cooled by liquid nitrogen and was found to be more than 95% pure by 13C NMR.The structure proof for 1 is based on the mass spectrum1 la (m/e 146 (M+)), the IR spectrum1 la (v 3040 cm-1), the NMR spectrum ((CeDe) 2.36-1.06 (multiplet and two distinctive doublets at 2.12 and 1.08, J = 4 Hz1 lb)), and the 13C NMR spectrum ((C6D6) b 64.4 (d,

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