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Effects of inert organic and inorganic anions on the rates of intramolecular general base‐catalyzed reactions of ionized phenyl salicylate (PS − ) with piperidine in the presence of cationic micelles
Author(s) -
Khan M. Niyaz,
Yusoff Rapandy
Publication year - 2001
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/1099-1395(200102)14:2<74::aid-poc333>3.0.co;2-5
Subject(s) - chemistry , reaction rate constant , bromide , cationic polymerization , micelle , medicinal chemistry , aqueous solution , piperidine , intramolecular force , base (topology) , catalysis , inorganic chemistry , polymer chemistry , stereochemistry , organic chemistry , kinetics , mathematical analysis , physics , mathematics , quantum mechanics
Pseudo‐first‐order rate constants ( k obs ) for piperidinolysis of PS − follow the relationship k obs − k 0 = k n obs [Pip] T ([Pip] T = total concentration of Pip) at a constant [CTABr] T (total concentration of cetyltrimethylammonium bromide), [MX] (inert salt concentration) and 35 °C. The values of k n obs at different [CTABr] T (ranging from 0.005 to 0.02 M ) and [MX] follow the relationship k n obs = ( k n W + k n W Ψ [MX] + k ns M K N K S 0 [CTABr] T )/( 1 + Ψ [MX] + K S 0 [CTABr] T ), where k n W = k n obs at [CTABr] T = [MX] = 0, Ψ is an empirical parameter and K S 0 is the CTABr micellar binding constant of PS − in the absence of MX. The magnitude of Ψ is attributed to the ability of X − to expel PS − from micellar pseudophase to the aqueous pseudophase. The values of Ψ vary in the order Ψ(sodium cinnamate) > Ψ(sodium 4‐methoxybenzoate) > Ψ(sodium 2‐chlorobenzoate) > Ψ(disodium isophthalate) > Ψ(disodium phthalate) > Ψ(sodium sulfate) > Ψ(disodium fumarate). The values of k ns M K N ( k ns M = k n M / V M , where k n M is the second‐order rate constant for the reaction of Pip with PS − in the micellar pseudophase and V M is the micellar molar volume in M −1 and K N represents CTABr micellar binding constant of Pip) are not significantly affected by the presence of MX into the reaction mixtures. Copyright © 2000 John Wiley & Sons, Ltd.