title: Substituent effects on partition coefficients of barbituric acids.
abstract: Precise partition coefficients in 1-octanol-water at 25 degrees C were determined for three 2-thiobarbituric acids and 14 barbituric acids with a wider range of substituents. The experimental log P values (log Pexp) of barbituric acids were correlated with the carbon number and the branching effect of the C5 substituent(s) by linear regression analysis. The carbon number term makes a major contribution to the partition coefficients. The contribution of the polar effect of the C5 substituents was insignificant in contrast to a previous report. Hydrophobic constants (pi) were determined for allyl, phenyl, and chloro-substituents, and these empirical pi values gave much closer predicted calculated log P (log Pcalc) values when applied to the reported log Pexp values.
authors.affiliation: Department of Pharmacy, University of Otago, Dunedin, New Zealand.
authors.forename: O
authors.initials: O
authors.lastname: Wong
authors.forename: R H
authors.initials: RH
authors.lastname: McKeown
mesh_terms: D001463:Barbiturates / Q000032:analysis* / Q000138:chemical synthesis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D012995:Solubility
chemical_list: D001463:Barbiturates