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Comparative kinetic study of solvent effects in the reactions of 1,2‐dinitrobenzene with butylamine and piperidine
Author(s) -
Chiacchiera S. M.,
Cattana R. I.,
Singh J. O.,
Anunziata J. D.,
Silber J. J.
Publication year - 1989
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.610020806
Subject(s) - chemistry , piperidine , medicinal chemistry , leaving group , solvent effects , nucleophile , photochemistry , chlorobenzene , solvent , nucleophilic substitution , ether , organic chemistry , catalysis
The kinetics of the aromatic nucleophilic substitution ( S N Ar) reactions of 1,2‐dinitrobenzene (1,2‐DNB) with butylamine (BA) and piperidine (PIP) were investigated as a function of the amine concentration and temperature, in chloroform, ethyl acetate, tetrahydrofuran (THF), acetonitrile (ACN), dimethylformamide (DMF), dimethyl sulphoxide (DMSO). benzene, toluene, chlorobenzene and diisopropyl ether. In the set of solvents consisting of ethyl acetate, THF, ACN, DMF and DMSO, neither reaction is catalysed ( k A = k 1 ). The sequence and range of reactivity for BA and PIP are similar in these solvents. These results indicate that reactions in which nitro in the leaving group behave differently from S N Ar reactions with other leaving groups, such as halogens or alkoxy groups, since an intramolecular hydrogen bond may be expected between the leaving nitro group and the ammonium H of the nucleophiles. The correlations of the rate coefficients obtained with Taft and Kamlet's solvatochromic method support these conclusions. On the other hand, these reactions show mild acceleration with relatively non‐polar solvents such as the aromatics and diisopropyl ether. The donor properties of these solvents and experiments with solvent mixtures suggest the formation of electron donor–acceptor complexes between them and 1,2‐DNB. Hence the preferential solvation of 1,2‐DNB by the donor solvent accounts for the mechanism observed.