Rates of reaction of OH- with methyl naphthalene-2-sulfonate (MeONs) in aqueous cationic surfactants (C16H33NR3OH), R = Me, Et, n-Pr, n-Bu, and cetylquinuclidinium hydroxide) increse with increasing surfactanta and hydoxide ion cocentrations. The variations of rate constants can be fitted to an equation that describes the distribution of both reactants between water and micelles in terms of Langmuir isotherms. The Langmuiur coefficients for OH- decrease in the head-group sequence Me3N > quinuclidinium > Et3N > Pr3N > Bu3N. The second rate constants at the micellar surface are not very sensitive to the bulk of the head group, although they increase at high added OH-Rate constants for attack of water on micellar-bound substrate increase with increasing bulk of the head group.
Micellar Head-Group Size and Anion Nucleophilicity in SN2 Reactions
GERMANI, Raimondo;SAVELLI, Gianfranco;
1990
Abstract
Rates of reaction of OH- with methyl naphthalene-2-sulfonate (MeONs) in aqueous cationic surfactants (C16H33NR3OH), R = Me, Et, n-Pr, n-Bu, and cetylquinuclidinium hydroxide) increse with increasing surfactanta and hydoxide ion cocentrations. The variations of rate constants can be fitted to an equation that describes the distribution of both reactants between water and micelles in terms of Langmuir isotherms. The Langmuiur coefficients for OH- decrease in the head-group sequence Me3N > quinuclidinium > Et3N > Pr3N > Bu3N. The second rate constants at the micellar surface are not very sensitive to the bulk of the head group, although they increase at high added OH-Rate constants for attack of water on micellar-bound substrate increase with increasing bulk of the head group.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
