Katritzky, Kucharskn, and Rowe 3093 * The determination was done by potentiometric titration using an E.I.L. model 23A directreading pH meter. Other results were obtained on a Unicam S.P. 500 spectrophotometer with 0 . 1 ~potassium dihydrogen phosphate-dipotassium hydrogen phosphate buffer for proton addition t o 2-phenacylpyridine, and in standard sodium hydroxide for the other compounds.predominates in aqueous solution for all the potentially tautomeric compounds, and that the KT are 220,2,000,000, and 450 for the 2-, 3-, and 4-series, respectively. The phenacylpyridines are all somewhat weaker as bases than pyridine (pK, = 5-21>, reflecting the l

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The tautomerism of 4-hydroxy-and 4-mercapto-cinnolines is re-examined by study of the ultraviolet spectra of these compounds and their 0-, S-, and N-methyl derivatives. 4-Hydroxycinnolines usually undergo predominantly 2-alkylation giving anhydro-base (I), with little, if any, 1 -alkylation to give l-alkyl-lcinnolone (11). These results are attributed to the dominance of steric factors in the alkylation reaction, particularly since 3-substituted 4-hydroxycinnolines give only 1-alkyl-4-cinnolone even when the 3-substituent is electron-donating.An effective process for bromination of 4-hydroxycinnoline is described and the resulting 3-bromo-4-hydroxycinnoline is alkylated to give l-alkyl-3bromo-4-cinnolone. Catalytic hydrogenation then provides l-alkyl-4cinnolone much more efficiently than by direct alkylation of 4-hydroxycinnoline. The cyanoethylation of 3and 4-hydroxycinnolines is discussed.

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