Kinetic Investigation of the Reactions Between Triphenylphosphine, Dialkyl Acetylenedicarboxilates and NH-Acid, such as 5,6-Dimethyl Benzimidazole by the UV Spectrophotometry Technique

The work was undertaken to carry out kinetic studies of the reactions between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of NH-acid, such as 5,6-dimethyl benzimidazole. To determine the kinetic parameters of the reactions, they were monitored by UV spectrophotometery. The second order fits were automatically drawn by the software associated with the UV instrument at an appropriate wavelength. The values of the second order rate constant (k_2) were automatically calculated, using standard equations within the program. At the temperature range studied, the dependence of the second order rate constant (ln k_2) on reciprocal temperature was in agreement with the 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, the structure of the reactants (different alkyl groups within the dialkyl acetylenedicarboxylates)and, also, the concentration of the reactants on the rate of the reactions.