Specific and nonspecific solvent effects on aromatic nucleophilic substitution. Kinetics of the reaction of 1-fluor-2,6-dinitrobenzene and homopiperidine in binary solvent mixtures

P.M. MANCINI, G. FORTUNATO, C. ADAM, L.R. VOTTERO, AND A. TERENZANI

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY

J. Wiley & Sons Ltd

Lugar: Illinois, USA; Año: 2002 vol. 15 p. 258 - 269

0894-3230

This paper presnts a comparative study of the solvent effects on the kinetic of the reactions between 1-fluor-2,6-dinitrobenzene and hexahydro-1H-azepine in ethyl acetate + chloroform or acetonitrile and acetinitrile + chloroform binary solvent mixtures. The propouse was to asses the contributionof each molecular microscopic sovent property to the oeverall sovation effect of the reaction critical state. The influence of the dipolatity/polarizability, hydrogen-bond donor acidity and hydrogen-bond acceptor basicity of the solvent mixtures on the reaction rate was analyzed by the application of the muktiparametric approach of Kamlet, abboud, Taft. The evatualtion of the corrlation coefficients shows that the solvation effects are dominated by the non-specific interactions. Moreover, the incidence of the hydrogen-bond acceptor solvent ability is more important than that correponding to the hydrogen-bond donor character, except for the reactions that manifest kinetic retarding effects. The influence of the solvation effects on the base catalysis was analyzed, describing the response patterns of the partial rate coefficciendts to the mixtures composition and also to each solvent propety. The application of a preferential solvation model to the kinetic results yields information on the preferential solvation of the reaction critical state by anay of the pure solvents, or by the hydrogen-bonded complexed media.