Effect of cationic gemini surfactants on the hydrolysis of carboxylate and phosphate esters using hydroxamate ions
| Autor: | Sunita Bal, Pierluigi Quagliotto, P. R. Dafonte, Manmohan L. Satnami, Sancheeta Kolay, Kallol K. Ghosh |
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| Rok vydání: | 2007 |
| Předmět: |
Ammonium bromide
Polymers and Plastics SPACER CHAIN-LENGTH NUCLEOPHILIC-SUBSTITUTION REACTION P-NITROPHENYL ACETATE MICELLAR MEDIA DEPHOSPHORYLATION ACIDS REACTIVITY CATALYSIS REAGENTS CLEAVAGE Inorganic chemistry Medicinal chemistry Chloride chemistry.chemical_compound Hydrolysis Colloid and Surface Chemistry Reaction rate constant Materials Chemistry medicine Ammonium Carboxylate Physical and Theoretical Chemistry Cationic polymerization chemistry Pyridinium medicine.drug |
| Zdroj: | Colloid and Polymer Science. 286:293-303 |
| ISSN: | 1435-1536 0303-402X |
| Popis: | The kinetics of the hydrolysis of p-nitrophenyl acetate (PNPA) and p-nitrophenyl diphenyl phosphate (PNPDPP) by hydroxamate ions mediated by gemini surfactants with quaternary ammonium bromide (16-n-16,2Br−, n = 3, 4, 6, 12) and pyridinium chloride (12py-n-py12,2Cl−, n = 3, 4) head group have been investigated at 27 °C. The gemini surfactant with the pyridinium head group, 12-py-4-py12,2Cl− (tetramethylene-1,4 bis dodecylpyridinium chloride) shows a large rate acceleration effect than that with an ammonium head group, 16-12-16,2Br−, relative to those in water. The apparent pK a of the hydroxamic acids have been determined in the presence of gemini surfactants. Catalytic system N-phenylbenzohydroxamate/12py-4-py12,2Cl− demonstrated over ~1,590-fold and ~255-fold rate enhancement in the hydrolysis of PNPA and PNPDPP, respectively, for the identical reaction performed in buffer aqueous media at 27 °C. The second order rate constant and binding constants for reactions were determined employing pseudophase model for micellar catalysis. |
| Databáze: | OpenAIRE |
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