Abstract

M. Zakarianezhad¹, S. M. Habibi-Khorassani²*, M. T. Maghsoodlou² and B. Makiabadi³

Kinetic studies have been made for synthesis of stable phosphorus ylids in the presence of different NH-acids, such as Imidazole, 2-Methylimidazole or 4-Methylimidazole (as a protic/nucleophilic reagent). At different temperature range studied, the dependence of the second order rate constant (ln k₂) and (ln k₂/T) on reciprocal temperature was in a good agreement with Arrhenius and Eyring equations. This provided the relevant plots to calculate the activation parameters (Ea, ?H^*, ?S^* and ?G^*) of all reactions. Furthermore, useful information were obtained from studies of the effect of solvent, structure of reactants (dialkyl acetylenedicarboxylates) and also concentration of reactants on the reaction rates. Proposed mechanism was confirmed according to the obtained results and steady state approximation, first and third steps (k₂ and k₃) of all reactions was recognized as a rate determining and fast steps, respectively on the basis of experimental data.

Stable phosphorus ylides; Dialkyl acetylenedicarboxylates; NH-acid; heterocyclic compounds; Kinetic studies

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