The E1cb route for ester hydrolysis; volumes of activation as an additional criterion of mechanism
作者:Neil S. Isaacs、Tariq S. Najem
DOI:10.1039/p29880000557
日期:——
of esters which possess an acidic proton at the α or vinylogous position can, in principle, hydrolyse by the E1cb route via a ketenoid intermediate. To the kinetic evidence for such a mechanism in the hydrolyses of 4-hydroxybenzoates, malonates, acetoacetates and fluorenecarboxylates is now added the further criterion of volumes of activation. Values of ΔV‡ for reactions proceeding by the E1cb route
The 2,4-dinitrophenylation of thiol or amino group with 1,2,4-trinitrobenzene proceeded quantitatively at pH 8.5 and 30 °C. The rate of S-dinitrophenylation was ≈104 times faster than that of N-dinitrophenylation. So this reaction can be used for both the determination of thiol even in the presence of large excess amine and the specific modification of thiol in proteins.
硫醇或氨基与 1,2,4-三硝基苯的 2,4-二硝基苯基化反应在 pH 8.5 和 30 °C 下定量进行。 S-二硝基苯基化的速率比N-二硝基苯基化的速率快约104倍。因此,该反应既可用于在存在大量过量胺的情况下测定硫醇,又可用于蛋白质中硫醇的特异性修饰。
Elimination–addition mechanisms of acyl-group transfer reactions: a novel E1cB mechanism in the hydrolysis of 2,4-dinitrophenyl 4-hydroxybenzoate
作者:Sergio Thea、Giuseppe Guanti、Giovanni Petrillo、Andrew Hopkins、Andrew Williams
DOI:10.1039/c39820000577
日期:——
Evidence is offered for the intermediacy of an unprecedented para-oxoketen intermediate in a dissociative mechanism for the hydrolysis of the title ester.