Steric and electronic effects on the mechanism of nucleophilic substitution (SNAr) reactions of some phenyl 2,4,6-trinitrophenyl ethers with aniline and N-methylaniline in acetonitrile and in dimethyl sulfoxide
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Date
2002-10-28
Authors
Isanbor, C
Crampton, M.R
Emokpae, T
Journal Title
Journal ISSN
Volume Title
Publisher
Perkin
Abstract
Rate data are reported for the reactions of a series of 3 - and 4 -substituted phenyl 2,4,6-trinitrophenyl ethers, 4, with
aniline in acetonitrile, leading to 2,4,6-trinitrodiphenylamine. The main reaction flux occurs through a base catalysed
pathway involving formation of a zwitterionic intermediate, equilibrium constant K1, and rate-limiting proton
transfer to base, rate constant kAn. The effects of ring substituents on values of rate and equilibrium constants are
discussed. In contrast the corresponding reactions in DMSO involve both uncatalysed and base catalysed pathways.
Reactions of 4 with N-methylaniline are extremely slow, but values of rate constants for reaction of 4-nitrophenyl
2,4,6-trinitrophenyl ether were measured using 1
H NMR spectroscopy. The value of the parameter K1kAn is lowered
by a factor of 105
for N-methylaniline relative to aniline in both acetonitrile and in DMSO. This reduction is
attributed to increased steric hindrance both in formation of the intermediate and to proton transfer.
Description
Keywords
Research Subject Categories::NATURAL SCIENCES::Chemistry::Physical chemistry::Spectroscopy , DMSO , nucleophilic aromatic substitution
Citation
Isanbor, C., Emokpae, T. A., & Crampton, M. R. (2002). Steric and electronic effects on the mechanism of nucleophilic substitution (SN Ar) reactions of some phenyl 2, 4, 6-trinitrophenyl ethers with aniline and N-methylaniline in acetonitrile and in dimethyl sulfoxide. Journal of the Chemical Society, Perkin Transactions 2, (12), 2019-2024.