S. Alunni et al., The Hammett equation applied to the nucleophilic displacement of ions and ion pairs on substituted benzenesulphonates, J PHYS ORG, 14(5), 2001, pp. 265-270
Nucleophilic substitution on meta- and para-substituted methyl benzenesulph
onates was studied with two chloride salts with different structures: NBu4C
l or KCl-Kryptofix 2,2,2. Treating the results with the Acree equation show
s that the reaction proceeds by two reaction paths, one involving the chlor
ide ion and the other, slower one, involving the ion pairs. Treating the re
sults with the Hammett equation gives consistent data, and shows that rho i
s positive and nearly the same for the two reaction paths (rho approximate
to +2). The reactivity of methyl p-nitrobenzenesulphonate was compared with
that of the corresponding ethyl derivative. and it is shown that the methy
l derivative reacts faster than the ethyl derivative in both paths. The res
ults are interpreted based on the assumption that in both paths a negative
charge is developed on the leaving group in the transition state, and that
the activated complex is linear. Copyright (C) 2001 John Wiley and Sons, Lt
d.