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Mn(III) complexes of meso-tetra(o,o′-dichlorophenyl)porphyrin, tetra-tert-butyl-tetraazaporphine and 3,5-octanitrophthalocyanine are efficient catalysts of naphthalene oxidation by peracetic acid in acetonitrile solution. The pathways of the reaction and the nature of intermediates and final products depend on the catalyst structure. For meso-tetra(o,o′-dichlorophenyl)porphyrin MnCl and tetra-tert-butyl-tetraazaporphine MnCl the single primary oxidation product is 1-naphthol. For 3,5-octanitrophthalocyanine MnCl, two pathways of naphthalene oxidation yielding 1-naphthol (as the primary product) and 1,4-naphthoquinone are proposed. The pathway of 1,4-naphthoquinone formation in the 3,5-octanitrophthalocyanine MnCl-catalysed reaction seems to involve two intermediates, 1,4-endo-peroxy-1,4-dihydro- and 2,3-epoxy-1,4-endo-peroxy-1,2,3,4-tetrahydronaphthalene.

The kinetics and mechanism of hydrogen absorption in Ti600 alloy were investigated at various temperatures (873K ≤ T ≤ 1123K). The rate of hydrogen absorption and equilibrium hydrogen pressure increased with the increase of temperature. Because hydriding reaction is an exothermic reaction, solubility of hydrogen decreased with increasing temperature. The experiment results were interpreted from the time dependent hydrogen absorption curves using various rate equations to reveal the mechanism of the hydrogen absorption processes. The hydriding reaction rate constants were extracted from the time-dependent hydrogen absorption curves. The mechanism of hydriding reaction in different stages has been analyzed. It was found that the chemical reaction process dominated the hydrogen absorption process at 923K. The chemical reaction process and the three-dimensional diffusion process dominated the hydrogen absorption process at 973K or higher.

As a first step toward the understanding of the aminolysis reaction of β-sultam compounds, the ammonolysis and the effect of a second ammonia on the ammonolysis reactions of N-methyl β-sultam have been studied using Density Functional Theory (DFT) method at the B3LYP/6-31G* level. The exploration of the reaction processes proposed two different mechanisms: concerted and stepwise mechanisms. There is one pathway in concerted mechanism and two pathways in stepwise mechanisms: pathways a and b. The calculations of reaction energy barriers show that the nonconcerted route is the more favored one. Solvent effects were assessed by the PCM method. The results show that the pathway a in channel II is the most favorable in both cases. The presence of solvent disfavors the reaction, and the participation of ammonia in the ammonolysis reaction plays a positive role and reduces the active energy greatly. All transition states in the assisted ammonolysis are 45–65 kJ/mol lower than those for the non-assisted reaction. The results also show that the ammonolysis reaction have a higher energy barrier than the alcoholysis reaction. This low reactivity of amines is also observed in the reactions of N-benzoyl β-sultam and p-nitrophenyl toluene-p-sulfonate where there is a distinct preference towards oxygen nucleophiles.

The reaction mechanisms and kinetics for DMS + O₃ ⇒ DMSO + O₂ in water vapor are studied using density functional theory. A series of reaction pathways are determined with molecular clusters containing the reacting species and up to three water molecules. The results show that the energy barrier, defined as the energy difference between the reactant complex and the transition state, decreases progressively as each water molecule is added to the reacting system. A decreasing energy barrier is attributed to favorable electrostatic interactions between the reacting species and water at the transition state and at the more polar product. Rate constants for the second-order reactions, involving different combinations of hydrated reactants up to three water molecules, are calculated using transition state theory with Eckart tunneling corrections. Effective rate constants for DMS + O₃ ⇒ DMSO + O₂ are obtained using the calculated second-order rate constants and the concentrations of hydrated reactants present in saturated water vapor. The results show that the rate of reaction for DMS + O₃ ⇒ DMSO + O₂ increases dramatically in the presence of water vapor, by up to seven orders of magnitude for reactions involving three water molecules. The study implies that the gas-phase reaction of DMS with ozone is significant in the troposphere and can greatly influence the global climate.

Direct dynamics within the framework of DFT has been used to study the reaction between Boron trichloride and H radical. Two sets of trajectories amounting to a total of 40 were simulated for different collision sites and initial velocities. Two reactive channels have been found. One is a Cl atom abstraction channel and the other is a Cl atom elimination channel. The detailed mechanisms of both reactive channels were depicted by sampling trajectories. For the first channel, the reaction mechanism proposed by ab initio calculations was represented. For the second channel, transition state was mapped out after the dynamics simulation.

The reaction mechanisms of HNCS with CH₂CH radical have been investigated by density functional theory (DFT). The geometries and harmonic frequencies of the reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311++G(d,p) level. The results show that the reaction is very complicated. Nine possible reaction pathways were identified. The results show that the most feasible reaction channel is the hydrogen-transfer pathway CH₂CH + HNCS → IMA1 → TSA1 → CH₂CHH + NCS. The pathway VIC C-S addition channel (CH₂CH + HNCS → TSD5 → IMD4 → TSD9 → CH₂CHS + CNH) can also occur easily. Ethene and radical NCS is the main product of the studied reaction, and product P8 (CH₂CHS and CNH) may also be observed. Compared with our previous study on the reaction HNCS + CH₂CH, the present reaction is easier to proceed.

The reaction mechanism of the activation of ethane by nickel atom has been investigated by density functional theory (DFT). The geometries and vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311 + +G(d, p) level. Two main pathways, C–C bond activation and C–H bond activation, are identified. In former channel, the rate-limiting step is found to be hydrogen-transferring step with a high barrier of 227 kJ · mol^-1. In the C–H bond activation pathway, the second hydrogen-transferring step is the rate-determining step of the whole reaction. The barrier of the step is 71 kJ · mol^-1. Our results show that the studied reaction would undergo along C–H bond activation pathway to form the products H₂ molecule and Ni⋯ethene complex. The present theoretical work indicates that Ni atom is more active than Ni⁺ cation in activating ethane.

Density functional theory has been used to study Rh(I)-catalyzed hydroacylation of ethene or ethyne. All the intermediates and the transition states were optimized completely at the B3LYP/6-311++G(d,p) level (LANL2DZ(d) for Rh, P). Calculation results confirm that Rh(I)-catalyzed hydroacylation of ethene is exothermic and the total released energy is -54 kJ/mol, and that Rh(I)-catalyzed hydroacylation of ethyne is also exothermic and the total released energy is -122 kJ/mol. In Rh(I)-catalyzed hydroacylation, ethene and ethyne have similar reactivity. Rh(I)-catalyzed oxidative addition of aldehyde is the rate-determinating step for the Rh(I)-catalyzed hydroacylation of ethene or ethyne. Hydrogen transfer reaction is prior to the C–C bond-forming reaction for Rh(I)-catalyzed hydroacylation of ethene. Thus hydrogen transfer reaction and the C–C bond-forming reaction may be co-existed for Rh(I)-catalyzed hydroacylation of ethyne. The effect of solvent in the hydroacylation of ethyne is greater than that in the hydroacylation of ethene.

The complex potential energy surface for the self-reaction of CH₂ClO₂ radicals, including 12 intermediates, 33 interconversion transition states, and 21 major dissociation products, was theoretically probed at the CCSD(T)/cc-pVDZ//B3LYP/6-311G(2d,2p) level of theory. The geometries and relative energies for various stationary points were determined. Based on the calculated CCSD(T)/cc-pVDZ potential energy surface, the possible mechanism for the studied system was proposed. It is shown that the most feasible channels are those leading to 2²CH₂ClO + ³O₂, ²CH₂ClO + ²HO₂ + CHClO, ²CH₂ClO + HCl + ²CH(O)O₂, ²CH₂ClO + ³O₂ + ²Cl + CH₂O, and p,s,o-CH₂ClOOOCl + CH₂O with the energy barriers of 5.6, 11.8, 12.4, 12.4, and 13.5 kcal/mol, respectively. Their mechanisms are that CH₂ClO₂ and CH₂ClO₂ form a tetroxide intermediate first, then the intermediate dissociates to yield the productions or through multi-steps reactions to produce the final products.

The reaction of N (⁴S) radical with NCO (X²Π) radical has been studied theoretically using density functional theory and ab initio quantum chemistry method. The triplet electronic state [N₂CO] potential energy surface (PES) is calculated at the G3B3 and CCSD(T)/aug-cc-pVDZ//B3LYP/6-311++G(d,p) levels of theory. All the energies of the transition states and isomers in the pathway RP1 are lower than that of the reactants; the rate of this pathway should be very fast. Thus, the novel reaction N + NCO can proceed effectively even at low temperatures and it is expected to play a role in both combustion and interstellar processes. On the basis of the analysis of the kinetics of all pathways through which the reactions proceed, we expect that the competitive power of reaction pathways may vary with experimental conditions for the title reaction.

The reaction mechanism of CuI-catalyzed formation of ethyl 2-phenylacetoacetate by arylation of ethyl acetoacetate has been investigated by density functional theory (DFT) using Becke's three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional (B3LYP). The geometries of the reactants, intermediates, transition states, and products have been optimized and verified by means of vibration frequency calculations. According to our assumption, this reaction can be divided into two stages. The rate-determining step is found to be the 3 → 4-TS procedure, which is the first procedure of stage 1. The low energy barrier of 39.85 kcal/mol indicates that this reaction can be carried out, which is in accordance with the experimental facts. For comparison, we have investigated the reaction mechanism of the same chemical reaction without CuI catalyst, whose energy barrier of rate-determining step is 212.76 kcal/mol higher than that with CuI catalyst. This fact suggests that CuI catalyst accelerates the reaction by remarkably lowering the energy barrier. The solvation effects on the barriers of the reaction are important. But the energetic order in DMSO solvent seems to be almost the same as that in gas-phase, which indicates that our conclusion achieved in gas-phase is believable. Our findings reveal the microscopic catalytic mechanism of CuI and are in agreement with the experimental facts.

Intramolecular amide hydrolysis of N-methylmaleamic acid is revisited at the B3LYP/6-311G(2df, p)//B3LYP/6-31G(d, p) + ZVPE level, including solvent effects at the CPCM-B3LYP/6-311G(2df, p)//Onsager-B3LYP/6-31G(d, p) + ZPVE level. The concerted reaction mechanism is energetically favorable over stepwise reaction mechanisms in both the gas phase and solution. The calculated reaction barriers are significantly lower in solution than in the gas phase. In addition, it is concluded that the substituents of the four N-methylmaleamic acid derivatives considered herein have a significant effect on the gas-phase reaction barriers but a smaller, or little, effect on the barriers in solution.

The mechanism of the reaction CF₃CHFO₂ + NO was investigated using ab initio and density functional theory (DFT). The optimized geometries for all stationary points on the reaction energy surface were calculated using MP2 and B3LYP methods with the aug-cc-pVDZ basis set. Single-point energy calculations were performed using the coupled cluster method with single, double and perturbative triple configurations, CCSD(T). The most important energy minima on the potential energy surface (PES) were found corresponding to two conformers of the peroxynitrite association adducts, cis-CF₃CHFOONO and trans-CF₃CHFOONO, and the nitrate, CF₃CHFONO₂. The radical pairs (CF₃CHFO + NO₂) and the nitrate are formed through the breaking of the peroxy bond of trans-CF₃CHFOONO and the rearrangement of cis-CF₃CHFOONO, respectively. The nitrate can be decomposed to carbonylated species (CF₃CHO or CF₃CFO), nitryl fluoride (NO₂F), nitrous acid (HONO), and radical pairs (CF₃CHFO + NO₂), which are of potential atmospheric importance.

Cysteine dioxygenase (CDO) catalyzes the oxidation of cysteine to cysteine sulfinate, which has crucial roles in the metabolism and bioconversion. The catalyzed reaction mechanism of CDO is currently disputed. Herein, a high-spin "Fe-proximal oxygen" catalytic mechanism of rat CDO is theoretically investigated with an energy barrier of 15.7 kcal⋅mol^-1. In the mechanism, the Fe-proximal oxygen atom firstly attacks the sulfur atom of cysteine by the swing of O(1)–O(2) bond, and this makes the Fe-proximal oxygen atom O(1) accessible to S and Fe-terminal oxygen atom O(2) be closed to Fe. Then the generated seven-membered ring intermediate has smaller tension and could help the reaction take place easily. The reaction ends in the formation of the product cysteine sulfinic acid with the second oxygen atom O(2) transferred to S. This study gives an additional insight of the reaction mechanism of CDO, where the "Fe-proximal oxygen" and "Fe-terminal oxygen" mechanisms are both favorable in the catalytic process.

Stereodynamics of the reaction Li + HF (v = 0,j = 0) → LiF + H and its isotopic variants on the ground electronic state (1²A′) potential energy surface (PES) are studied by employing the quasiclassical trajectory (QCT) method. At a collision energy of 2.2 kcal/mol, product rotational angular momentum distributions, P(θ_r) and P(ϕ_r), are calculated in the center-of-mass (CM) frame. The results demonstrate that the product rotational angular momentum j^′ is not only aligned along the direction perpendicular to the reagent relative velocity vector k, but also oriented along the negative y-axis. The four generalized polarization-dependent differential cross sections (PDDCSs) are also computed. The PDDCS₀₀ distribution shows a sideways scattering for the reaction Li + HF and a strongly backward scattering for the reaction Li + DF. However, it displays both the forward and backward scatterings for the reaction Li + TF. These features demonstrate that the Li + HF and Li + DF reactions proceed predominantly through the direct reaction mechanism. However, the Li + TF reaction undergoes both the direct and indirect reaction mechanisms. The PDDCS_21- distribution indicates that the product angular distributions are anisotropic.

The reaction mechanism of SiHF radical with HNCO has been investigated by the B3LYP method of density functional theory (DFT), while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311++G** level. To obtain more precise energy result, stationary point energies were calculated at the CCSD(T)/6-311++G**//B3LYP/6-311++G** level. In temperature range of 100 K to 1900 K, the statistical thermodynamics and Eyring transition state theory with Winger correction are used to study the thermodynamic and kinetic characters of the channel with low energy barrier at 1.0 Atm. SiHF + HNCO → IM8 → TS8 → SiFNHCHO(P3) was the main channel with low potential energy in the singlet state, SiFNHCHO was the main product. The analyses for the combining interaction between SiHF radical and HNCO with the atom-in-molecules (AIM) theory have been performed. There are three reaction channels in the triplet.

Calculations based on density functional theory (DFT) have been carried out for the gas-phase ion-molecule reactions of CS₂ with CHX^•- (X = F, Cl, and Br) to investigate the effect of the halogen-substituent on the reaction mechanism. The doublet potential energy surfaces (PESs), involving two striking reaction patterns named by the middle-C attack and the end-S attack in terms of anion attack on the C and S atoms of CS₂, have been explored and characterized in detail. Compared with the results of the end-S attack, reaction with the middle-C attack pattern displays more efficiency on PES. For a given reaction pattern, the reactions of CHCl^•- and CHBr^•- occur with similar efficiencies and reactivity trends. The CHF^•- anion displays remarkably different reactivity, which is traced to its lower electron binding energy and the effect of the electronegative fluorine substituent. This is in good agreement with the experimental observation. According to the property of the product branching ratios in experiment, dynamical effect is used to evaluate the reason that the end-S attack with less energetically favorable obtained in our theoretical studies is comparable to the middle-C attack.

The catalytic coupling reaction mechanism for the transformation from p-aminothiophenol (PATP) to 4,4′-dimercaptoazobenzene (4,4′-DMAB) on silver cluster was studied by the density functional theory. All the reactants, intermediates, transition states and products were optimized with B3LYP method at 6-311+G (d, p) basis set (the LanL2DZ basis set was used for Ag atom). Transition states and intermediates have been confirmed by the corresponding vibration analysis and intrinsic reactions coordinate (IRC). In addition, nature bond orbital (NBO) and atoms in molecules (AIM) theories have been used to analyze orbital interactions and bond natures. Consistent with the conclusions reported in the literature, the core of obtaining the production of azobenzene according to the coupling reaction of PATP absorbed on Ag₅ clusters is the elimination of two H atoms. Meanwhile, we find that the effect of illumination in that reaction matters a lot. We also found in PATP molecular that the synergistic catalytic effect of S end absorbed on the catalyzer draws dramatically evident under no illumination conditions, while it draws less obvious under light. According to the paper's conclusion, PATP absorbed on the surface of Ag₅ tends to generate azobenzene easily.

Chlorine-containing organic compounds have been of major interest since such compounds would serve as temporary reservoirs for HO_X, RO_X and ClO_X radicals. Moreover, it would transport chlorine species to the atmosphere and stratosphere. However, limited studies have been performed on the 2-chlorinated ethyl hydroperoxide. In this work, the mechanism of unimolecular dissociation of 2-chlorinated ethyl hydroperoxide is theoretically studied. The equilibrium structures are optimized at the Boese–Martin for kinetics (BMK) level. And the energies are further refined at the Balanced multi-coefficient correlation-coupled cluster theory with single and double excitations (BMC-CCSD) level on the basis of the optimized geometries. Fifteen reaction channels are finally confirmed including the direct C–O, O–O, O–H, and C–C bond cleavage or the H₂-, H₂O-, H₂O₂-, and CH₃Cl-elimination.

DFT calculations have been carried out to study the detailed mechanisms of the carboxylative cyclization reaction between propargylic alcohols and CO₂ catalyzed by N-Heterocyclic Olefins (NHO), as well as the molecular orbital theory. Results indicated that this type of reaction prefers a three steps mechanism controlled by free NHO rather than to be catalyzed by the NHO–CO₂ adducts. For the first step, CO₂ promotes the hydrogen transfer from alkynol to NHO to form the carboxylate, in which propargylic alcohols was deprotonated by the free NHO acted as the catalyst precursor to form the alkynol anion; meanwhile, alkynol anion captures carbon dioxide to form the carboxylate. We found this CO₂ promoting Hydrogen abstraction mechanism would decrease the reaction energy barrier and increase releasing heat of this reaction. Secondly, a five-membered-ring intermediate is easily formed to generate carboxylate via an intramolecular ring-closing reaction. Finally, the production generated through a protonating process.