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KMID : 1059519940380100753
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Journal of the Korean Chemical Society
1994 Volume.38 No. 10 p.753 ~ p.762
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Chemical Reactions in Surfactant Solutions (Ⅳ) : Micellar Rate Effect on Reactions of Hydroxide and o-Iodosobenzoate Ions with Organic Phosphinates
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Hong Young-Seuk
Kim Hyun-Muk
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Abstract
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Dephosphorylation of diphenyl- or isopropylphenyl-4-nitrophenylphosphinate (DPNPIN or IPNPIN) mediated by OH- or o-iodosobenzoate ion (IB-) are relatively slow in aqueous solution. The reactions in CTAX micellar solutions are, however, very accelerated, because CTAX micelles can accommodate both reactants in their Stern layer in which they can easily react, while hydrophilic OH-(or IB-) and hydrophobic phosphinates are not mixed in water. Even though the concentrations (> 10-3 M) of OH-(or IB-) in CTAX solutions are much larger amounts than those (6 × 10-6 M) of phosphinates, the rate constants of the dephosphorylations are largely influenced by change of the concentration of the ions, which means that the reactions are not followed by the pseudo first order kinetics. In comparison to effect of the counter ions of CTAX in the reactions, CTACl is more effective on the dephosphorylation of DPNPIN (or IPNPIN) than CTABr due to easier expelling of Cl- ion by OH-(or IB-) ion from the micelle, because of easier solvation Cl- ion by water molecules. The reactivity of IPNPIN with OH-(or IB-) is lower than that of DPNPIN. The reason seems that the 'bulky' isopropyl group of IPNPIN hinders the attack of the nucleophiles. The mechanism of reaction of IPNPIN with IB- ion concluded as 'nucleophilic' instead of 'general basic' by a trapping experiment and a measured kinetic isotope effect.
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KEYWORD
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