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Kinetics and mechanism for the formation of o ‐carboxy( N ‐methyl)‐benzohydroxamic acid in the cleavage of ethyl N ‐[ o ‐( N ‐methyl‐ N ‐hydroxycarbamoyl)‐benzoyl]carbamate in N ‐methylhydroxylamine, acetate, and phosphate buffers
Author(s) -
Khan M. Niyaz
Publication year - 2003
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.10142
Subject(s) - chemistry , reaction rate constant , medicinal chemistry , benzoic acid , catalysis , methyl acetate , kinetics , cleavage (geology) , buffer solution , stereochemistry , organic chemistry , geotechnical engineering , quantum mechanics , fracture (geology) , engineering , physics
The rate of cleavage of ethyl N ‐[ o ‐( N ‐methyl‐ N ‐hydroxycarbamoyl)benzoyl]‐ carbamate (ENMBC) in the buffer solutions containing N ‐methylhydroxylamine, acetate + N ‐methylhydroxylamine, and phosphate + N ‐methylhydroxylamine followed an irreversible consecutive reaction path: ENMBC where A and B represent N ‐hydroxyl group cyclized product of ENMBC and o ‐( N ‐methyl‐ N ‐hydroxycarbamoyl)benzoic acid, respectively. Both rate constants k 1 obs and k 2 obs showed the presence of buffer catalysis, but buffer catalysis turned out to be weak in the presence N ‐methylhydroxylamine buffer, while it was strong in the presence of acetate and phosphate ones. Buffer‐independent rate constants k 10 and k 20 increased linearly with the increase in a OH with definite intercepts. The values of molar absorption coefficient of A , obtained under varying total buffer concentrations at a constant pH, showed the presence of a fast equilibrium: A + CH 3 NHOH ⇆ C , where C represents N ‐[ o ‐( N ‐methyl‐ N ‐hydroxycarbamoyl)methyl]benzohydroxamic acid. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 427–437, 2003