N-ヘテロ芳香族の電子的性状(第31報) : 発ガン性物質4-Nitroquinoline 1-Oxideとニコチン酸アミドとの相互作用

抄録

A spectrophotometric study was made on the interaction of the carcinogen 4-nitroquinoline 1-oxide (4-NQO) with nicotinamide, and formation of a charge-transfer complex, in which n-electron of the ring nitrogen of nicotinamide is transferred tothe π-system of 4-NQO was presumed from the following results : (1) A new absorption band characteristic of chargetransfer complex was exhibited in the vicinity of 402 mμ in the difference spectra of aqueous mixtures of nicotinamide and 4-NQO vs. 4-NQO. (2) Analysis of the new absorption band through the Benesi-Hildebrand's equation revealed that a complex of 1 : 1 molar ratio was formed. (3) Intensity of the absorption band decreased in acid region below pH corresponding to pK_a of nicotinamide. (4) Intensity of absorption band, which was produced around 396 mμ in the difference spectra of mixed system of 1-methylnicotinamide and 4-NQO was not infiuenced by variation of pH. (5) In the case of mixed system of nicotinamide and 4 -nitropyridine 1-oxide, whose electron affinity is smaller than that of 4-NQO, difference band appeared at about 340 mμ, i.e., in the shorter wave length region than that of the NA-4-NQO system. The magnitudes of ε, K, ΔH, and ΔS values were consistent with the above presumption. Examination of solvent effect revealed that the new absorption bands arose from n→π^* transition.