Substituent effects on electrophilic catalysis by the carbonyl group: anatomy of the rate acceleration for PLP-catalyzed deprotonation of glycine.

ABSTRACT: First-order rate constants, determined by (1)H NMR, are reported for deuterium exchange between solvent D(2)O and the α-amino carbon of glycine in the presence of increasing concentrations of carbonyl compounds (acetone, benzaldehyde, and salicylaldehyde) and at different pD and buffer concentrations. These rate data were combined with (1)H NMR data that define the position of the equilibrium for formation of imines/iminium ions from addition of glycine to the respective carbonyl compounds, to give second-order rate constants k(DO) for deprotonation of α-imino carbon by DO(-). The assumption that these second-order rate constants lie on linear structure-reactivity correlations between log k(OL) and pK(a) was made in estimating the following pK(a)'s for deprotonation of α-imino carbon: pK(a

SUBMITTER: Crugeiras J 

PROVIDER: S-EPMC3060797 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature