Kinetic study of the reactions of <i>p</i>‐nitrophenyl acetate and <i>p</i>‐nitrophenyl benzoate with oximate nucleophiles

Tiwari, Shuchi; Kolay, Sancheeta; Ghosh, Kallol K.; Kuča, Kamil; Marek, Jan

doi:10.1002/kin.20363

Cited by 19 publications

(27 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First-order rate constants for the nucleophilic substitution reaction of PNPA with monopyridinium oximes (2-PAM, 3-PAM, and 4-PAM) were determined under pseudo-first-order condition, i.e., nucleophiles were in large excess over the substrates in the presence and absence of surfactants with the same hydrophobic chain length (C 16 ) and varying hydrophilic head groups. Cationic micelles bring reactants closer by hydrophobically binding of substrate and coulombically attracting negatively charged nucleophile.…”

Section: Resultsmentioning

confidence: 99%

“…The rate enhancement in the phosponium-and pyridinium-based cationic surfactants is greater than in alkyl ammonium head groups due to their bulky head group [22,40]. The effect would correspond to a general decrease in the polarity of the head group region that would therefore increase the rate of the nucleophilic substitution [16,41]. Another possible explanation is the steric effects by the phenyl rings in the head group region that would activate the bound substrate toward substitution [33].…”

Section: Kinetic Rate Constants Above the Cmcmentioning

confidence: 93%

See 1 more Smart Citation

Hydrolysis of carboxylate and phosphate esters using monopyridinium oximes in cationic micellar media

Singh

Ghosh

Marek

et al. 2011

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

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 pnitrophenyldiphenyl phosphate with oximate ions ( CH NO − ) 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 (pK a ) of the investigated oximes have been determined spectrophotometrically. C

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Kinetic Rate Constants Above the Cmcmentioning

confidence: 93%

Hydrolysis of carboxylate and phosphate esters using monopyridinium oximes in cationic micellar media

Singh

Ghosh

Marek

et al. 2011

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

show abstract

“…It has been already proved that cationic surfactants accelerate the reaction. According to Buncel et al [26], the electrostatic attraction of the cationic head groups of the surfactants at the micelle surface to the nucleophilic anion counterions leads to augmentation of the local concentration of the nucleophile, whereas incorporation of the substrate in the micelle leads to a higher local concentration of There is little information about the effect of the variation of head groups on the micellar structure [27][28][29].…”

Section: Scheme 1 Nucleophilic Substitution Reaction Of Different Estmentioning

confidence: 98%

Comparative study of nucleophilic efficacy of pralidoxime towards phosphorus, sulfur and thiophosphorus based esters

Tiwari

Ghosh

Marek³

et al. 2009

React Kinet Catal Lett

Self Cite

View full text Add to dashboard Cite

show abstract

“…Hydrolysis and nucleophilic reactions of carboxylate and phosphate esters are involved in many biological processes . The nucleophile‐aided hydrolysis is the most preferred reaction for the detoxification organophosphorus toxic compounds . In this regard, many α‐effect nucleophiles such as o‐ iodosylcarboxylate , peroxides , oximates , hypochlorites , and hydroxamates have been investigated alone or as functionalized surfactants.…”

Section: Introductionmentioning

confidence: 99%

O‐Nucleophilicity of Hydroxamate Ions for Cleavage of Carboxylate and Phosphate Esters in Cationic Micelles

Satnami

Karbhal

Dewangan

2014

Int J of Chemical Kinetics

View full text Add to dashboard Cite

The nucleophilic reactivities of hydroxamate (HA−) ions of the structure RCONHO− [R = CH3 (acetohydroxamate, AHA−), C6H5 (benzohydroxamate, BHA−), 2‐OHC6H4 (salicylhydroxamate, SHA−), and 4‐CH3OC6H4 (4‐methoxbenzohydroxamate, MBHA−)] for the hydrolysis of p‐nitrophenyl benzoate (PNPB), tris(3‐nitrophenyl) phosphate (TRIS), and bis(2,4‐dinitrophenyl) phosphate (BDNPP) have been examined kinetically. Over the pH range of 6.7–11.4, the α‐nucleophile (HA−) accelerates deacylation of PNPB and dephosphorylation of TRIS (in cetyltrimethylammonium bromide (CTAB) micelle, 2.0 × 10−3 M). The salicylhydroxamate ion encountered effective catalysis than AHA−, BHA−, and MBHA− ions. The monoanionic SHA− and dianionic SA2− forms of salicylhydroxamic acid are the reactive species. The hydroxamic acid concentration–dependent critical micelle concentration (cmc) and fractional ionization constant (α) and of CTAB provide qualitative information for the micellar incorporation of the hydroxamate ion. The ab initio calculations performed on the hydroxamate ions at restricted Hartree–Fock using the 6‐311G (d,p) basis set revealed the O‐nucleophilicity of hydroxamate ions toward C=O and P=O centers. On the basis of ab initio calculation, it has been concluded that hydroxamic acids can exist into E‐amide and Z‐amide forms. The large stable amide or imide anions of hydroxamate are strong nucleophilic for the esterolytic cleavage of carboxylate and phosphate esters.

show abstract

Kinetic study of the reactions of p‐nitrophenyl acetate and p‐nitrophenyl benzoate with oximate nucleophiles

Cited by 19 publications

References 35 publications

Hydrolysis of carboxylate and phosphate esters using monopyridinium oximes in cationic micellar media

Hydrolysis of carboxylate and phosphate esters using monopyridinium oximes in cationic micellar media

Comparative study of nucleophilic efficacy of pralidoxime towards phosphorus, sulfur and thiophosphorus based esters

O‐Nucleophilicity of Hydroxamate Ions for Cleavage of Carboxylate and Phosphate Esters in Cationic Micelles

Contact Info

Product

Resources

About