The spontaneous (SN2) hydrolysis of methyl naphthalene-2-sulfonate (MeONs) in water is inhibited by cationic, anionic and zwitterionic micelles of the following surfactants, CTAOMs, n-C16H33N+Me3MeSO3-; CTPAOMs, n-C16H33N+Pr3MeSO3-; SDS, C12H25OSO3-Na+; SB3-14, n-C14H29N+Me2(CH2)3SO3-SBBu3-14,n-C14H29N+Bu2(CH2)3SO3-; DMMAO, n-C14H29N+Me2O-; DPMAO, n-C14H29N+Pr2O-. Rate constants, krel, relative to those in water, are in the range 0.55–0.63 for all the cationic and zwitterionic micelles including the protonated amine oxides. The value of krel in anionic micelles of SDS is 0.22, but NaClO4 sharply decreases krel 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 head groups with the initial and transition states.
Effects of micellar head group structure on the spontaneous hydrolysis of methyl naphtalene-2-sulphonate. The role of perchlorate ion
SPRETI, Nicoletta;
1998-01-01
Abstract
The spontaneous (SN2) hydrolysis of methyl naphthalene-2-sulfonate (MeONs) in water is inhibited by cationic, anionic and zwitterionic micelles of the following surfactants, CTAOMs, n-C16H33N+Me3MeSO3-; CTPAOMs, n-C16H33N+Pr3MeSO3-; SDS, C12H25OSO3-Na+; SB3-14, n-C14H29N+Me2(CH2)3SO3-SBBu3-14,n-C14H29N+Bu2(CH2)3SO3-; DMMAO, n-C14H29N+Me2O-; DPMAO, n-C14H29N+Pr2O-. Rate constants, krel, relative to those in water, are in the range 0.55–0.63 for all the cationic and zwitterionic micelles including the protonated amine oxides. The value of krel in anionic micelles of SDS is 0.22, but NaClO4 sharply decreases krel 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 head groups with the initial and transition states.Pubblicazioni consigliate
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