General base catalysis in the decomposition of N‐Cl‐Valine in aqueous solution

Abstract

This article analyzes the kinetics of the decomposition of N-C1-Valine in aqueous solution, which is formed rapidly by chlorination of Valine with sodium hypochlorite. A general-base catalyzed process not yet described is reported. The experimental evidence shows two competitive decomposition paths: an unimolecular concerted fragmentation process (k = (1.8 ? 0.1) .s-l at 298 K) and the other one is an E2 elimination process whose importance increases with pH and depends on the nature and the concentration of the bases present in the medium.

Absolute rate constants for the formation of nitrogen-centred radicals from chloramines/amides and their reactions with antioxidants

“…The calculated values are very similar to molar absorption coefficients that have been determined for other chloramines (ε = 340-370 M Ϫ1 cm Ϫ1 ) using different experimental methods. 30, 31 The molar absorption coefficients for the two cyclic chloramide compounds could not be determined due to interfering absorbances from the parent compounds themselves, and other reaction products.…”

Degradation Mechanisms and Substituent Effects of N-Chloro-α-Amino Acids: A Computational Study

“…Scheme 1 demonstrates that the ΔG ≠ of this step for N-Cl-Gly is approximately 23 kcal/mol with an estimated rate constant k of ∼10 −5 s −1 , and those for N-Cl-Ala and N-Cl-Val are approximately 19−20 kcal/mol with k between 1.5 × 10 −2 and 7.9 × 10 −2 s −1 , as presented in Table 1, which agrees well with the experimental rate constants k of ∼10 −6 for the former and 10 −4 s −1 for the latter. 23,24,26,34 Notably, the Grob fragmentation for N-Cl-Gly is kinetically less feasible than those for N-Cl-Ala and N-Cl-Val, which is attributed to the presence of the alkyl groups increasing the electron density of the C atom.…”

Pressure and pH dependence of the kinetics of decarboxylative dechlorination of N-chloro-l-alanine

“…In order to investigate the applicability of the theory to reaction rates we sought a reaction whose kinetic solvent effects would not be confounded by secondary influences, such as solvent effects on pH. The decomposition of N-chloro-aamino acids in the neutral solution range possesses the following features, very attractive for our purposes: ( I ) the kinetics are first-order, and the reaction is unimolecular; (2) the reaction rate is independent of pH over the approximate range 4 to 13 [5,7,8]; (3) the rate-determining step of the process is not a solvolysis; and (4) the reaction is known to display a sensitivity to solvent composition [8]. In support of the solvent effect work, we have conducted further mechanistic studies, which we report here.…”

“…and it is conventional to take the value of the slope at P = 0 (or P = 1 bar, which is practically the same thing) for use in eq. (7). Since there is no theory relating k to P, many empirical approaches have been described for extracting the desired quantity [27-291.…”