Premium
A mechanistic viewpoint of the reaction between 1‐fluoro‐2,6‐dinitrobenzene and alicyclic amines in the ethyl acetate–chloroform system
Author(s) -
Mancini P. M.,
Fortunato G. G,
Vottero L. R.
Publication year - 2005
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.869
Subject(s) - chemistry , chloroform , ethyl acetate , solvent , piperidine , arrhenius equation , mole fraction , solvent effects , organic chemistry , activation energy
A study was made of the influence of temperature on the reactions between 1‐fluoro‐2,6‐dinitrobenzene and each of the secondary amines pyrrolidine, piperidine and homopiperidine (hexahydro‐1 H ‐azepine), carried out in ethyl acetate–chloroform binary solvent mixtures. It involved the analysis of both global activation parameters and the corresponding Arrhenius plots from the k A values at three amine concentrations. These values were obtained by carrying out the reactions at 5, 15, 25, 40 and 50°C over the whole range of chloroform mole fraction. The analysis of Arrhenius lines allowed us to prove the existence of isokinetic relationships, which were used as a diagnostic tool in order to infer a changeover in the nature of the rate‐determining transition state as a function of solvent composition. The experimental evidence together with theoretical quantum mechanical calculations suggest that the reactions with the secondary amines explored carried out in pure ethyl acetate and ethyl acetate–chloroform solvent mixture at X CHCl 3 = 0.1 and in some cases also at X CHCl 3 = 0.3 proceed via the formation of a six‐membered orientated dipolar aggregate in which the specific base–general acid (SB–GA) mechanism may take place. The reactions carried out in the remaining solvent mixtures evolve towards the classical SB–GA mechanism. Copyright © 2004 John Wiley & Sons, Ltd.