Stochastic Model of Unimolecular Reactions and the RRKM Theory

Theoretical studies on CuCl-catalyzed C-H activation/C-O coupling reactions: oxidant and catalyst effects

Copper-complex catalyzed coupling reactions have been widely applied in the production of many important organic moieties from a synthetic perspective. In this work, a series of density functional theory (DFT) calculations, employing the B3LYP + IDSCRF/DZVP method, have been performed for a typical CuCl-catalyzed C-O cross-coupling reaction. The novel reaction mechanism was reported as four successive processes: oxidative radical generation (ORG) or oxidative addition (OA), hydrogen abstraction (HA), C-H activation/reductive elimination, and separation of product and recycling of catalyst (SP & RC). Our calculations provided a deep understanding on the dissimilar chemical activities associated with varying the oxidants used; detailed energy profile analyses suggested that the first oxidation process could proceed via either of the two competing channels (ORG and OA mechanisms) which is the basis to explain the different experimental yields. In addition, our molecular modelling gave theoretical evidence that Cu(ii) → Cu(i) reduction by solvent DMF (and a water molecule) might serve as a preliminary step to produce some more active Cu(i) species that could subsequently be oxidized into Cu(iii) favorably. In contrast, the Cu(ii) → Cu(iii) direct pathway was estimated to be prohibited from thermodynamics. All the calculation results in this work are parallel with the experimental observations.

Theoretical estimation of kinetic parameters for nucleophilic substitution reactions in solution: an application of a solution translational entropy model

The kinetic parameters, such as activation entropy, activation enthalpy, activation free-energy, and reaction rate constant, for a series of nucleophilic substitution (SN) reactions in solution, are investigated using both a solution-phase translational entropy model and an ideal gas-phase translational entropy model. The results obtained from the solution translational entropy model are in excellent agreement with the experimental values, while the overestimation of activation free-energy from the ideal gas-phase translational entropy model is as large as 6.9 kcal mol(-1). For some of the reactions studied, such as and in methanol, and and in aqueous solution, the explicit + implicit model, namely, a cluster-continuum type model, should be employed to account for the strong solvent-solute interactions. In addition, the explicit + implicit models have also been applied to the DMSO-H2O mixtures, which would open up a door to investigate the reactions in a mixed solvent using density functional theory (DFT) methods.

A DFT kinetic study on 1,3-dipolar cycloaddition reactions in solution

Several popular density functional theory (DFT) methods have been employed to characterize a series of 1,3-dipolar cycloaddition reactions, including the exploration of reaction mechanisms and the calculations of kinetic parameters.

Anharmonic Effect on Unimolecular Reactions with Application to the Photodissociation of Ethylene

The importance of anharmonic effect on dissociation of molecular systems, especially clusters, has been noted. In this paper, we shall present a theoretical approach that can carry out the first principle calculations of anharmonic canonical and microcanonical rate constants of unimolecular reactions within the framework of transition state theory. In the canonical case, it is essential to calculate the partition function of anharmonic oscillators; for convenience, the Morse oscillator potential will be used for demonstration in this paper. In the microcanical case, which involves the calculation of the total number of states for the activated complex and the density of states for the reactant, we make use of the fact that both the total number of states and the density of states can be expressed in the inverse Laplace transformation of the partition functions and that the inverse Laplace transformation can in turn be carried out by using the saddle-point method. We shall also show that using the theoretical approach presented in this paper the total number of states and density of states can be determined from thermodynamic properties and the difference between the method used in this paper and the thermodynamic model used by Krems and Nordholm will be given. To demonstrate the application of our theoretical approach, we chose the photodissociation of ethylene at 157 and 193 nm as an example.