Kinetic investigation of the reactions between triphenylphosphine, dialkyl acetylenedicarboxylates and NH-acid such as 7-azaindole by the UV spectrophotometry

Abstract

Kinetic studies of the reactions between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of NH-acid, such as 7-azaindole are reported here. Kinetic parameters of the reactions have been monitored by UV spectrophotometery. The second order fits have been automatically drawn and the values of the second order rate constant (k₂) calculated using standard equations within the program. At the temperature range studied, dependence of second order rate constant (Ln k₂) on reciprocal temperature is in agreement with Arrhenius equation. This provides the relevant plots to calculate the activation energy of all reactions. Studies on the effect of solvent, structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates) and also concentration of reactants on the rate of reactions have been made. Proposed mechanism has been confirmed according to the obtained results and steady state approximation and first step (k₂) of reaction recognized as the rate determining step on the basis of experimental data.