Substituent effects on partition coefficients of barbituric acids
Precise partition coefficients in 1-octanol-water at 25°C were determined for three 2-thiobarbituric acids and 14 barbituric acids with a wider range of substituents. The experimental log P values (log P(exp)) 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 (π) were determined for allyl, phenyl, and chloro-substituents, and these emperical π values gave much closer predicted calculated log P (log P(calc)) values when applied to the reported log P(exp) values.
Wong,McKeown
p. 926 - 932
(2007/10/02)
Synthesis and reactions of some N-mono- and N,N'-bis-salicyloyl derivatives of barbituric acid
N,N'-Bis-salicyloyl derivatives unlike the N-mono-salicyloyl derivatives of barbituric acid underwent thermal decomposition. The decomposition products depend on the size of the substituents in the position 5. When one of them is phenyl, salicyloyl radicals are split off without cleavage of the barbituric ring.
Sladowska
p. 447 - 456
(2007/10/02)
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