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Hydrolysis of carboxylate and phosphate esters using monopyridinium oximes in cationic micellar media
Author(s) -
Singh Namrata,
Ghosh Kallol K.,
Marek Jan,
Kuca Kamil
Publication year - 2011
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.20590
Subject(s) - chemistry , iodide , bromide , cationic polymerization , hydrolysis , micelle , oxime , carboxylate , phosphate , micellar solutions , reaction rate constant , dissociation constant , medicinal chemistry , pulmonary surfactant , organic chemistry , kinetics , aqueous solution , biochemistry , physics , receptor , quantum mechanics
The reactions of p ‐nitrophenyl acetate (PNPA) with a series of monopyridinium oximes, viz. 2‐PAM (2‐hydroxyiminomethyl‐1‐methylpyridinium iodide), 3‐PAM (3‐hydroxyiminomethyl‐1‐methylpyridinium iodide), and 4‐PAM (4‐hydroxyiminomethyl‐1‐methylpyridinium iodide) have been studied in the presence of cationic surfactants of same hydrophobic chain length (C 16 ) within the concentration range of 0.5–6.0 mM at pH 8.0 under the pseudo‐first‐order condition. The observed rate constant ( k obs ) increases with increasing surfactant concentration culminating into a maximum, and this has been analyzed in detail following the concepts of micellar catalysis. The structure–activity relationship of the investigated oximes has been discussed, and 2‐PAM was found to be the most reactive among all the three investigated oximes for the cleavage of PNPA. Esterolytic decomposition of p ‐nitrophenyldiphenyl phosphate with oximate ions (CHNO − ) was followed in cetyltrimethylammonium bromide micelles at pH 9.0, and 4‐PAM was the most reactive oxime for the micellar hydrolysis of phosphate ester. The apparent acid dissociation constants (p K a ) of the investigated oximes have been determined spectrophotometrically. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 569–578, 2011