Dephosphorylation and Aromatic Nucleophilic Substitution in an Alkoxide Functionalized Micelle

Article abstract of DOI:10.1021/j150644a037

Dephosphorylation of p-nitrophenyl diphenyl phosphate (pNPDPP) and aromatic nucleophilic substitution on 2,4-dinitrochlorobenzene and -naphthalene (DNCB and DNCN, respectively) have been examined in aqueous micelles of the functional surfactant hexadecyl(2-hydroxyethyl)dimethylammonium hydroxide, n-C16H33N⁺-Me2CH2CH2OHOH^- (2).The variation of the first-order rate constant, k_ψ, with concentration of 2 and OH^- can be fitted to equations which describe the distributions of substrate and OH^- between aqueous and micellar pseudophase.The first-formed products of aromatic nucleophilic substitution are ethers formed by attack of alkxide zwitterion, n-C16H33N⁺Me2CH2CH2O^- (2a).The ethers react with micellar-bound OH^- giving aryl oxide ion, and the rate constants for these slower reactions in relatively dilute OH^- can be fitted to a model which describes the distribution of OH^- between aqueous and micellar pseudophases.The second-order rate constants for reactions with 2a and OH^- in the micellar pseudophase can be estimated and compared with reactions of OH^- and a model alkoxide zwitterion, Me3N⁺CH2CH2O^-, in water.The rate constants in the micelles are larger than in water for aromatic nucleophlic substitution, but smaller than in water for dephosphorylation.The electrical conductivity of solutions of 2 is consistent with formation of the zwitterion 2a.