- Micellar Head-Group Size and Anion Nucleophilicity in SN2 Reactions
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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) increase with increasing surfactant and hydroxide ion concentrations.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 Langmuir coefficients for OH- decrease in the head-group sequence Me3N > quinuclidinium > Et3N > Pr3N > Bu3N.The second-order rate constants at the micellar surfaces 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.
- Bonan, Cristiana,Germani, Raimondo,Ponti, Pier Paolo,Savelli, Gianfranco,Cerichelli, Giorgio,et al.
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- Monoazo dyes, process for their preparation, and the use thereof
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The invention relates to monoazo dyes of the formula STR1 wherein K is the radical of a coupling component of the benzene, naphthalene or heterocyclic series, and R is hydrogen, halogen, carboxy, a C1 -C6 alkyl, C1 -C6 alkoxy, C2 -C6 alkanoylamino, C1 -C6 alkylsulfonylamino, C1 -C6 alkylsulfonyl, phenyl(C1 -C4)alkylsulfonyl or naphthyl(C1 -C4)alkylsulfonyl or benzoyl radical, which radicals may be further substituted, or is a STR2 group, wherein each of R1 and R2 independently of the other is hydrogen or a C1 -C6 alkyl, C5 -C7 cycloalkyl, phenyl or naphthyl radical, which radicals may be further substituted, and wherein X is hydrogen, halogen or a C1 -C6 alkyl, C1 -C6 alkoxy, C2 -C6 alkanoylamino or C1 -C6 alkylsulfonylamino radical, which radicals may be further substituted. These dyes give dyeings of good light- and wetfastness properties on polyamide material.
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