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Derivatives of squaric acid, 1,2-dihydroxycyclobutenedione (la), have been prepared and studied. 1,2-Dimethoxycyclobutenedione (lb) was prepared from la. It is readily hydrolyzed to 1 -hydroxy-2-methoxycyclobutenedione (Ic): with water kw = 1.2 X -6 M-1 sec-1; with hydroxide kh = 1.2 X 102 sec-1. Ic is further hydrolyzed to la: with water kf ~2 X ICC7 M_1 sec-1; with hydroxide kf ~2 X KC1 M-1 sec-1. Compound lb was also converted to 1,2-diethoxycyclobutenedione (Id), to l-methoxy-2-aminocyclobutenedione (Ie), and to 1,2-diaminocyclobutenedione (If). In this set alkoxy compounds show ,"" ca. 250 µ, hydroxy compounds max ca. 265 µ, and amino compounds Xmax ca. 270 m,u; hydroxy-alkoxy and amino-alkoxy compounds show double maxima. The hydroxyls are strongly acidic, the alkoxyl compounds behave like reactive esters, and the amino compounds behave like high-melting acidic amides.

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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

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