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Leaving group effects on the mechanism of aromatic nucleophilic substitution ( S N Ar) reactions of some phenyl 2,4,6‐trinitrophenyl ethers with aniline in acetonitrile
Author(s) -
Crampton Michael R.,
Emokpae Thomas A.,
Howard Judith A. K.,
Isanbor Chukwuemeka,
Mondal Raju
Publication year - 2004
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.690
Subject(s) - chemistry , steric effects , deprotonation , aniline , sn2 reaction , acetonitrile , leaving group , nucleophile , nucleophilic substitution , intramolecular force , medicinal chemistry , substitution reaction , nucleophilic aromatic substitution , stereochemistry , organic chemistry , ion , catalysis
Kinetic studies are reported for the reactions with aniline in acetonitrile of a series of X‐phenyl 2,4,6‐trinitrophenyl ethers [X=H, 2‐, 3‐, 4‐CH 3 , 2,4‐, 2,6‐(CH 3 ) 2 , 2‐, 3‐, 4‐NO 2 , 2,4‐, 2,6‐(NO 2 ) 2 ]. X‐ray crystal structures for X=H, 2,6‐(CH 3 ) 2 and 2,6‐(NO 2 ) 2 are reported and provide evidence for steric crowding around the 1‐position of these molecules. Nevertheless, the kinetic data show that increasing substitution does not sterically inhibit nucleophilic attack by aniline and an ‘early’ transition state is likely. In general, the reactions are base catalysed; interpreted as rate‐limiting deprotonation of the zwitterionic intermediates. Only with the dinitro derivatives is an uncatalysed reaction involving intramolecular proton transfer observed and when X=2,6‐(NO 2 ) 2 this pathway takes all the reaction flux. Copyright © 2003 John Wiley & Sons, Ltd. Additional material for this paper is available in Wiley Intersciene