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The effect of medium on the alpha-effect: Nucleophilic substitution reaction of p-nitrophenyl diphenyl phosphinate with butane-2,3-dione monoximate and substituted phenoxides in cationic micelles

Title
The effect of medium on the alpha-effect: Nucleophilic substitution reaction of p-nitrophenyl diphenyl phosphinate with butane-2,3-dione monoximate and substituted phenoxides in cationic micelles
Authors
Limb, JKJeon, SELee, SEUm, IH
Ewha Authors
엄익환임진경
SCOPUS Author ID
엄익환scopusscopus; 임진경scopus
Issue Date
2002
Journal Title
BULLETIN OF THE KOREAN CHEMICAL SOCIETY
ISSN
0253-2964JCR Link
Citation
vol. 23, no. 9, pp. 1263 - 1266
Keywords
the alpha-effectmicellar effectbasicitynucleophilicityBronsted equation
Publisher
KOREAN CHEMICAL SOC
Indexed
SCI; SCIE; SCOPUS; KCI WOS scopus
Abstract
Pseudo-first-order rate constants (k(obs)) have been determined for the nucleophilic substitution reactions of p-nitrophenyl diphenyl phosphinate (PNPDPP) with substituted phenoxides (XC6H4O-) and butane-2,3-dione monoximate (Ox(-)) in 0.1 M borate buffer (pH = 10.0) at 25.0 +/- 0.1 degreesC. The k(obs) value increases sharply upon addition of cethyltrimethylammonium bromide (CTAB) to the reaction medium up to near 7 x 10(-4) M CTAB and then decreases smoothly upon further addition of CTAB. The rate enhancement upon the addition of CTAB is most significant for the reaction with -O2CC6H4O- and least significant for the one with C6H5O-, indicating that the reactivity of these aryloxides in the presence of CTAB cannot be determined by the basicity alone. The strength of the interaction of these anionic aryloxides with the positively charged micellar aggregates has been suggested to be an important factor to determine the reactivity in the presence of CTAB. The k(obs) value for the reaction with Ox(-) increases also upon the addition of CTAB. However, the increase in the k(obs) value is much more significant for the reaction with Ox(-) than for the one with ClC6H4O-, indicating that Ox(-) is less strongly solvated than ClC6H4O- in H2O. The alpha-effect shown by Ox(-) in H2O has been attributed to the ground-state solvation difference between Ox(-) and ClC6H4O-.
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자연과학대학 > 화학·나노과학전공 > Journal papers
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