Micellar effects upon the reaction of betaine esters with hydroxide ion

Hamad Al-Lohedan, Clifford A. Bunton, Laurence S. Romsted

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63 Scopus citations


The reaction of hydroxide ion with methyl N,N,N-trimethylglycinate (1a) is inhibited by cationic micelles of C14H29NMe3Cl and C16H33NMe3Cl (MTACl and CTACl) because the substrate is largely in the aqueous pseudophase which is depleted in OH- by the cationic micelles. Added Cl- displaces OH- from the micelles and decreases micellar inhibition. The corresponding reaction of methyl N-dodecyl-N,N-dimethylglycinate (1b) is catalyzed by both MTACl and CTACl which bind both reactants, but this catalysis is reduced by NaCl. Self-micellization of methyl N-hexadecyl-N,N-dimethylglycinate (1c) speeds reactions with OH-, and the rate constants reach plateau values with increasing substrate concentration and are independent of OH-. But addition of either CTACl or NaCl slows reaction because Cl- displaces OH- from the micelle. These diverse rate effects can be accounted for quantitatively in terms of the pseudophase ion-exchange model, which considers reactions in both the aqueous and micellar pseudophases and the distribution of both reactants between the pseudophases.

Original languageEnglish (US)
Pages (from-to)2123-2129
Number of pages7
JournalJournal of physical chemistry
Issue number14
StatePublished - 1981
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physical and Theoretical Chemistry


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