Mechanism investigation of stable phosphorus ylides derived from4-nitro aniline and different dialkyl acetyeledicarbixylates:Akinetic study

Author(s): Mohammad Zakarianejad, Sayyed Mostafa Habibi-Khorassani, Batoul Makiabadi, Hojjat Ghasempour

Kinetic studies were made of the reactions between triphenylphosphine 1, dialkyl acetylenedicarboxylates 2 in the presence of NH-acid, such as 4- nitro aniline (as a protic/nucleophilic reagent) 3. To determine the kinetic parameters of the reactions, theyweremonitored byUVspectrophotometery. The second order fits were automatically drawn and the values of the second order rate constant (k2) were automatically calculated using standard equationswithin the program.All reactions repeated at different temperature range, 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 fromstudies 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, k3) of all reactions was recognized as a rate determining and fast steps, respectively on the basis of experimental data.

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