EFFECTS OF MICELLAR HEAD GROUP-STRUCTURE ON THE SPONTANEOUS HYDROLYSIS OF METHYL NAPHTHALENE-2-SULFONATE - THE ROLE OF PERCHLORATE ION

The spontaneous (S(N)2) hydrolysis of methyl naphthalene-2-sulfonate ( MeONs) in water is inhibited by cationic, anionic and zwitterionic mic elles of the following surfactants, CTAOMs, n-C16H33N+Me3MeSO3-; CTPAO Ms, n-C16H33N+Pr3MeSO3-; SDS, C12H25OSO3-Na+; SB3-14, n-C14H29N+Me2(CH 2)(3)SO3-; SBBu3-14, n-C14H29N+Bu2(CH2)(3)SO3-; DMMAO, n-C14H29N+Me2O- ; DPMAO, n-C14H29N+Pr2O-. Rate constants, k(rel), relative to those in water, are in the range 0.55-0.63 for all the cationic and zwitterion ic micelles including the protonated amine oxides, The value of k(rel) in anionic micelles of SDS is 0.22, but NaClO4 sharply decreases k(re l) in SB3-14 from 0.56 to 0.15, These rate effects are not related to variations in substrate binding but depend upon interactions of the he ad groups with the initial and transition states.