Effect of different substituents on the one-pot formation of 3,4,5-substituted furan-2(5H)-ones: a kinetics and mechanism study

2016

J. Phys. Org. Chem.

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The effect of different substituents on the kinetics of the reactions between 2‐amino‐benzamide and some of benzaldehyde derivatives have been spectrally investigated in the presence of formic acid. The proposed mechanism were challenged due to the determination of rate‐determining step (RDS) and also, to obtain the general rate law of the reaction. For all substituents, the reactions followed the second‐order kinetics and the partial orders of reactions were recognized with respect to each reactant. Electron withdrawing substituents on benzaldehyde ring increased the rate of reaction. Kinetic values (k and Ea) and associated activation parameters (ΔH‡, ΔG‡ and ΔS‡) of the reactions were determined. Both the Arrhenius and the Eyring equations were used to calculate activation energy. Comparison of magnitude of and T showed that the reactions were enthalpy controlled. Isokinetic plots for the reactions were plotted and linear relationship between and recognized that relative contribution of enthalpy and entropy to the overall free energy was the same in the reactions.

Section: Introductionmentioning

confidence: 99%

An experimental investigation of substituent effects on the formation of 2,3-dihydroquinazolin-4(1H)-ones: a kinetic study

Mostafa

2016

J. Phys. Org. Chem.

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“…The stopped‐flow technique is most commonly used when fast reactions are involved , and in the present work there was a significant proof for determining the fast step of the reaction. Also, the kinetic data regarding the overall reaction was gained using the UV–vis spectrophotometry technique; this technique is generally preferred over IR and NMR spectroscopy because (a) it is more sensitive so more dilute solutions may be used and (b) water and other common solvents present fewer problems with UV–vis than with IR and NMR methods . Moreover, theoretical methods are used for obtaining thermodynamic and kinetic data that are important for the accepting prophecy of the chemical reaction mechanism and also a possible interpretation of experimental findings .…”

Section: Introductionmentioning

confidence: 99%

Experimental and Theoretical Insight into the Kinetics and Mechanism of the Synthesis Reaction of 2,3-Dihydro-2-phenylquinazolin-4(1H)-one Catalyzed in Formic Acid

Ebrahimi

et al. 2017

Int. J. Chem. Kinet.

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An efficient and simple method has been developed for the synthesis of 2,3‐dihydro‐2‐phenylquinazolin‐4(1H)‐one catalyzed in formic acid. Also, the synthesis reaction between benzaldehyde and 2‐aminobenzamid was monitored spectrally. On the basis of the kinetic data obtained by the UV–vis spectrophotometry, both the first and second steps of the speculative five steps mechanism were enabled to be a rate‐determining step and also reaction showed second‐order kinetics. Considering information obtained by the stopped‐flow technique indicated that the first step is certainly a fast step. Moreover, the reaction was energetically and thermodynamically evaluated using theoretical methods and results were profoundly compared with the experimental approaches. Herein, theoretical rate constants were obtained using potential energy surfaces and the transition state theory at the B3LYP/6–311+G** level of theory. The Winger method was also applied to describe the tunneling effects. Calculations showed that the second step was the rate‐determining step in accordance with the experimental data. It is also found that the oxidation step was the fastest step in the proposed mechanism. For all five steps, two possibilities were considered for generating the probable product by using the thermodynamic parameters and kinetic data. Thermodynamic parameters also showed an exothermic reaction.

“…In previous works, we have investigated the kinetics of the syntheses of some new organic compounds such as phosphorus ylides, pyran derivatives, phosphonate esters, and so on, both experimentally and theoretically . Experimental procedures suffer from various constraints, such as trapping the transition states (TSs) or intermediates, in corroborating the pathway through which the reactions proceed.…”

Section: Introductionmentioning

confidence: 99%

Insight into the Reaction Mechanism of α‐Amino Phosphonate Synthesis Using Succinic Acid as a Catalyst: Computational Kinetic Approach

Yaghoubian

2017

J Chinese Chemical Soc

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The reaction mechanism in the synthesis of particular α‐amino phosphonates from 4‐methyl benzaldehyde, aniline, and trimethyl phosphite in the presence of succinic acid is theoretically investigated. The profile of the potential energy surface is constructed at both HF/6‐31 + G(d,p) and B3LYP/6‐31 + G(d,p) levels of theory for evaluating all the steps involved in the reaction mechanism. In order to investigate the effect of the structure on reactivity, some para‐substituted benzaldehydes are subjected to kinetic examination. The overall reaction in the presence of electron‐withdrawing groups is thermodynamically much more favorable than in the presence of the electron‐donating groups; similarly, the reaction is kinetically more favorable and much easier in the presence of electron‐withdrawing groups. Moreover, step 2 (imine formation) is recognized as the rate‐determining step at both levels of theory. Also, step 1 is diffusion‐controlled with both electron‐withdrawing and electron‐donating groups, while the other steps are chemically controlled in the reaction mechanism.