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Rate constants are reported for reaction of 4‐substituted 1‐chloro‐2,6‐dinitrobenzenes 1, 6‐substituted 1‐chloro‐2,4‐dinitrobenzenes 2, and some of the corresponding 1‐phenoxy derivatives, 3 and 4, with n‐butylamine, pyrrolidine and piperidine in acetonitrile as solvent. Values of k1, the rate constant for nucleophilic attack at the 1‐position, increase with increasing ring‐activation but may be reduced by steric repulsion at the reaction centre which increases in the order Cl < OPh, and n‐butylamine < pyrrolidine ≈ piperidine. ortho‐Substituents may also have adverse steric effects, and those of the trifluoromethyl group are particularly serious. X‐ray crystal structures of phenyl 2,4‐dinitro‐6‐trifluoromethylphenyl ether and phenyl 2,6‐dinitro‐4‐trifluoromethylphenyl ether are reported. Base catalysis in the 1‐phenoxy derivatives is attributed to rate‐limiting proton transfer from the zwitterionic intermediates 6 to base. Values of rate constants for this process decrease with increasing steric congestion at the reaction centre and in the order n‐butylamine > pyrrolidine > piperidine. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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‐CH3, 2,4‐, 2,6‐(CH3)2, 2‐, 3‐, 4‐NO2, 2,4‐, 2,6‐(NO2)2]. X‐ray crystal structures for X=H, 2,6‐(CH3)2 and 2,6‐(NO2)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‐(NO2)2 this pathway takes all the reaction flux. Copyright © 2003 John Wiley & Sons, Ltd.Additional material for this paper is available in Wiley Intersciene

Rate constants are reported for the reactions of a series of 1-chloro-, 1-fluoro-and 1-phenoxy-nitrobenzenes activated by CF 3 or CN groups or by ring-nitrogen with n-butylamine, pyrrolidine or piperidine in acetonitrile. The results are compared with results reported previously for more strongly ringactivated compounds. Decreasing ring activation leads to lower values of k 1 for nucleophilic attack although this may be mediated by reduced steric congestion around the reaction centre. Specific steric effects, leading to rate-retardation,

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