Nucleophilic Heteroaromatic Substitution: Kinetics of the Reactions of Nitropyridines with Aliphatic Amines in Non-polar Aprotic Solvents.
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Journal of Scientific Research and Development
Rate data are reported for the reactions of a series of 2-phenoxy-3-nitrobenzenes, 4 and 2-phenoxy-5-nitrobenzenes 5 with n-butylamine, pyrrolidine or piperidine in toluene. The results are compared with results reported previously for reactions of the same substrates and nucleophile in acetonitrile and DMSO. While the reaction of 4 with n-butylamine in toluene is base catalysed the reaction in both acetonitrile and DMSO is not base catalysed. The reactions of 4 and 5 with pyrrolidine and piperidine in toluene and acetonitrile are base catalysed though with a_ slight difference in kinetic pattern as the plot of the overall second order rate constant, ka vs. [Am] for the reactions is linear with small negative intercept in toluene while that in acetonitrile is curvilinear with no intercept. Values of the microscopic rate constants obtained in foluene were lower compared to values in acetonitrile and in DMSO. The small negative intercepts indicates the presence of a third order term but this was found to make very little contribution to the overall reaction flux. Mechanism for the overall substitution process have been rationalised in terms of the proton transfer mechanism.
Research Subject Categories::NATURAL SCIENCES::Chemistry::Physical chemistry::Kinetics , Nucleophilic heteroaromatic substitution , Aliphatic amines , Base catalysis , solvent effects , substituent effects
Isanbor, C. (2011). Nucleophilic Heteroaromatic Substitution: Kinetics of the Reactions of Nitropyridines with Aliphatic Amines in Non-polar Aprotic Solvents. Journal of Scientific Research and Development (JSRD), 13(1).