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Paper | Regular issue | Vol 41, No. 2, 1995, pp.315-322
Published online, 1st January, 1970
DOI: 10.3987/COM-94-6940
Effect of Fluorine-Substitution on Basicity of Benzo[h]quinoline, Benzo[f]quinoline and Quinoline

Wei Wu, Ken-ichi Saeki, and Yutaka Kawazoe*

*Faculty of Pharmaceutical Sciences, Nagoya City University, Tanabedori, Mizuho-ku, Nagoya 467, Japan

Abstract

The effect of fluorine-substitution on the acid-dissociation constant was examined using 19 types of mono- and difluorinated derivatives of benzo[h]quinoline, benzo[f]quinoline and quinoline. Decrease in pKa were induced by fluorine substitution and were dependent on the number of bonds between the substituent F atom and the basic N atom, whereas pKa-increases were induced by a substituent F atom spatially interacting with the basic N atom. The spatial interaction between F and N was analyzed by means of a semiempirical molecular orbital method MOPAC PM3.