Effect of the Composition of the Aqueous Organic Solvent on the Kinetics of N-Acylation of α-Amino Acids with 4-Nitrophenyl 4-Nitrobenzoate

Equations relating the N-acylation rate constants of glycine, L--alanine, DL-threonine, and L-proline with 4-nitrophenyl 4-nitrobenzoate in water-acetonitrile, water-2-propanol, and water-2-methyl-2-propanol solvents to the composition of the medium were obtained, and reaction rate constants in water were calculated.     

Solvation bifunctional catalysis of the hydrolysis of sulfonyl chlorides by hydration complexes of 2-propanol: influence of the substrate structure

The temperature dependence of rate constants for the pseudo-first-order hydrolysis of 2-methylbenzenesulfonyl chloride, 1,5-naphthalenedisulfonyl chloride, and 4-acetamidobenzenesulfonyl chloride in water-2-propanol mixtures is studied in the i-PrOH mole fraction range x₂ = 0–0.10. The concentration dependences of the enthalpy of activation and the entropy contribution ( = 100(–TS)/(G, %) for the hydrolyses of all sulfonyl chlorides are nonmonotonic, depending on the sulfonyl chloride structure and the degree of complementarity of the hydration complexes to the solvent structure. The sulfonyl chlorides are hydrolyzed via two pathways: one of them involves a water dimer as a bifunctional catalyst along with a water molecule as a nucleophile, and the other involves an alcohol hydrate.Translated from Kinetika i Kataliz, Vol. 46, No. 1, 2005, pp. 35–43.Original Russian Text Copyright © 2005 by Ivanov, Mikhailov, Gnedin, Lebedukho, Korolev.     

Solvation Effects in Hydrolysis of 2-Methylbenzenesulfonyl Halides in Binary Solvents H2O-i-PrOH, H2O-t-BuOH, and H2O-1,4-Dioxane with Low Concentration of Organic Component

Activation parameters of hydrolysis of 2-methylbenzenesulfonyl chloride are studied, as influenced by the mole fraction of an alcohol in binary solvents H₂O-i-PrOH and H₂O-t-BuOH. The dependences of the activation parameters on the mole fraction of the second component (X ₂) are strongly nonmonotonic, like those for the previously studied hydrolysis of toluenesulfonyl chloride and bromide in aqueous dioxane. The position of the extrema along the composition axis is controlled by the hydrophobicity of nonelectrolytes. Sharp minima of H and S in the binary system H₂O-i-PrOH at X ₂ 0.03 are caused by specific solvation of the sulfonyl chloride.     

Kinetics of N-Acylation of Glycine and L-Proline with 4-Nitrophenyl 4-Nitrobenzoate in Aqueous-Organic Solutions

Kinetic characteristics (rate constants and activation energies and entropies) are determined for N-acylation of glycine and L-proline with 4-nitrophenyl 4-nitrobenzoate in water-acetonitrile, water-2-propanol, and water-2-methyl-2-propanol systems. With increasing water content in the system, the N-acylation rate constants increase and the activation energy and entropy decrease, which is due to features of solvation of the reagents and activated complex with aqueous-organic solvents.