title: A joint experimental and theoretical investigation of kinetics and mechanistic study in a synthesis reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of benzhydrazide.
abstract: Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine (TPP) and dialkyl acetylenedicarboxylates, in the presence of NH-acids, such as benzhydrazide. 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 (k(2)) were 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 compatible with Arrhenius equation. This provided the relevant plots to calculate the activation energy of all reactions. Furthermore, useful information were 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. On the basis of experimental data the proposed mechanism was confirmed according to the obtained results and a steady state approximation and the first step (k(2)) and third (k(3)) steps of the reactions were recognized as the rate determining steps, respectively. In addition, three speculative proposed mechanisms were theoretically investigated using quantum mechanical calculation. The results, arising from the second and third speculative mechanisms, were far from the experimental data. Nevertheless, there was a good agreement between the theoretical kinetic data, emerge from the first speculative mechanism, and experimental kinetic data of proposed mechanism.
authors: Department of Chemistry, University of Sistan and Baluchestan, Zahedan, Iran.
authors: Mohammad Amin
authors: MA
authors: Kazemian
authors: Sayyed Mostafa
authors: SM
authors: Habibi-Khorassani
authors: Ali
authors: A
authors: Ebrahimi
authors: Malek Taher
authors: MT
authors: Maghsoodlou
authors: Peyman Mohammadzadeh
authors: PM
authors: Jahani
authors: Mahbobeh
authors: M
authors: Ghahramaninezhad
mesh_terms: D000465:Algorithms; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry; D006834:Hydrazines / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D009943:Organophosphorus Compounds / Q000737:chemistry*; D010544:Peroxidases / Q000037:antagonists & inhibitors*; D012997:Solvents / Q000737:chemistry; D013386:Succinates / Q000138:chemical synthesis* / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D004791:Enzyme Inhibitors; D006834:Hydrazines; D009943:Organophosphorus Compounds; D012997:Solvents; D013386:Succinates; C061896:triphenylphosphine; D010544:Peroxidases; C006712:benzoylhydrazine