Home >> Progress in Reaction Kinetics and Mechanism, Volume 34, Number 1

Synthesis of Stable Phosphorus Ylides From 6-Chloro-2-Benzoxazolinone and Kinetic Investigation of the Reactions by UV Spectrophotometry

Authors: Kazemian, Mohammad Amin; Karimi, Pouya; Habibi-Khorassani, Sayyed Mostafa; Ebrahimi, Ali; Maghsoodlou, Malek Taher; Milani, Forough Jalili

Source: Progress in Reaction Kinetics and Mechanism, Volume 34, Number 1, 2009 , pp. 77-96(20)

Publisher: Science Reviews 2000 Ltd

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Abstract:

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1 : 1 : 1 addition reactions between triphenylphosphine and dialkyl acetylenedicarboxylates, in the presence of an NH-acid, such as 6-chlorobenzoxazolinone. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon-carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group. To determine the kinetic parameters of the reactions, they were monitored by UV spectrophotometry. The second order fits were drawn and the values of the second order rate constant (k2) were calculated automatically using standard equations within the program. Over the temperature range studied, the dependence of the second order rate constant (Ln k2) on reciprocal temperature was in a good agreement with the Arrhenius equation, leading to the activation energies of all reactions. Furthermore, useful information was obtained from studies of the effect of solvent, the structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates) and also the concentration of reactants on the rate of reactions. The proposed mechanism is consistent with the results obtained and the steady state approximation, and the first step (k2) of reaction was recognized as the rate-determining step on the basis of experimental data.
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  • Progress in Reaction Kinetics & Mechanism is an international journal for the quarterly publication of both in-depth reviews and research articles.

    In-depth reviews are comprehensive accounts bringing together work from many sources with the aim of providing an article of lasting value that will become established as the reference source in the particular subject. Research articles, on the other hand, normally focus on a relatively new or recently developed field or technique giving a state-of-the-art account of the subject and may well refer to a narrower range of existing work. It covers the fields of kinetics and mechanisms of chemical processes in the gas phase and solution of both simple and complex systems.

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