Theoretical Study, Kinetics and Mechanism Investigation of the Reactions Between Triphenylphosphine, Dialkyl Acetylenedicarboxilates And NH-Acid Such As 2-Ethylimidazole by UV

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Kinetic studies were made of the reactions between triphenylphosphine, dialkyl acetylenedicarboxylates in the presence of NH-acid, such as 2-ethylimidazole. To determine the kinetic parameters of the reactions, they were monitored by UV spectrophotometery. The second order fits were automatically drawn and the values of the second order rate constant (k2) were calculated using standard equations within the program. At the temperature range studied the dependence of the second order rate constant (Ln k2) on reciprocal temperature was in a good agreement with Arrhenius equation. This provided the relevant plots to calculate the activation energy of all reactions. Furthermore, useful information was obtained from studies of the effect of solvent, structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates) and also concentration of reactants on the rate of reactions. Proposed mechanism was confirmed according to the obtained results and steady state approximation and first step (k2) of reaction was recognized as a rate determining step on the basis of experimental data. In addition, assignment of more stabe isomers (Z or E) was investigated using the AIM theory.

Triphenylphosphine; UV spectrophotometry; Kinetic parameters; Geometrical isomer