Browsing by Author "Castro, Enrique A."
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Item Reactions of Aryl Acetates with Secondary Alicyclic Amines in Ethanol/Water Mixtures: Effect of the Solvent Composition on the Kinetics and Mechanism(2011) Castro, Enrique A.; Millan, Daniela; Aguayo, Raúl; Campodónico, Paola; Santos, José G.We report a kinetic study on the reactions of secondary alicyclic amines toward 4-nitrophenyl, 2,4-dinitrophenyl, and 2,4,6-trinitrophenyl acetates (1, 2, and 3) in ethanol/water mixtures of different compositions. It is found that (i) the intermediate in the reaction of 1 is stabilized in a mixture of 90 vol% ethanol; (ii) for the reaction of 2, the mechanism is stepwise in water but concerted in the mixtures; (iii) For the reaction of 3, the mechanism is concerted along the whole range of composition; (iv) the effect of -NO(2) outweighs the solvent effect; (v) preferential solvation in the core of reaction can be ruled out. (C) 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 687-693, 2011Item Reactivity of benzohydrazide derivatives towards acetylation reaction. Experimental and theoretical studies(2010) Campodónico, Paola; Aliaga, Margarita E.; Santos, José G.; Castro, Enrique A.; Contreras, RenatoWe herein report an experimental and theoretical study on the acetylation reaction of benzohydrazide derivatives towards p-nitrophenyl acetate (NPA). The kinetic data are consistent with a stepwise mechanism with the nucleophilic attack as the rate determining step. From the theoretical analysis it is found that benzohydrazide derivatives establish intramolecular proton rearrangement. The enol form appears as the active species for nucleophilic attack. A reaction mechanism incorporating keto-enol pre-equilibria is proposed. The study is completed with a local reactivity analysis describing the most reactive centers for nucleophilic attack together with a site activation analysis describing inductive substituent effect