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Abstract: A computational study of the [2+2] cycloaddition reaction pathways for formaldehyde–ketene and formaldehyde–isocyanic acid has been presented by using the DFT(B3LYP) method. These cycloaddition reactions could yield to eight different four-membered molecules. In the two considered reactions, the reactions for the β-propiolactone and oxazetidinone products have the lower barriers of 26.40 and 32.88kcalmol−1 and are exothermic by 27.68 and 4.00kcalmol−1, respectively. The β-propiolactone and oxazetidinone ring compounds have been predicted to be the most stable thermodynamically. Simulation of the solvent environment (toluene, THF, acetone, acetonitrile and water) has been investigated by using polarized continuum model method, yet only small differences have been found to occur in energetics between the studied structures in the gas-phase and in the solvent. [Copyright &y& Elsevier]

Abstract: A theoretical investigation at DFT (B3LYP) level on the cyclopropanation reactions catalyzed by nickel(0) and nickel(II) have been extensively investigated. The computation results show that the active catalytic species formed by a CH2 fragment and the Cl2Ni(PH3)2 is carbenoids (PH3)2Ni(CH2Cl)Cl (IMA) and (PH3)Ni(CH2PH3)Cl2 (IMB), but both the carbenes (Cl2NiCH2 (IMC), (PH3)3NiCH2 (IME) and (PH3)2NiCH2 (IMG)) and carbenoids (ClNiCH2Cl (IMD), Ni(CH2PH3)(PH3)2 (IMF) and Ni(CH2PH3)PH3 (IMH)) are active catalytic species obtained from NiCl2, Ni(PH3)3, Ni(PH3)2 and a CH2 fragment. The cyclopropanation reaction proceeds through either concerted or multistep reaction pathway. The most favor cyclopropanation reactions catalyzed by nickel(II) is multistep pathway for IMD with a barrier of 21.65kcalmol−1 but is endothermic 6.74kcalmol−1, and the most favor nickel(0) catalyzed cyclopropanation reactions is also multistep pathway for IME, IMH and IMG species all with barriers of 21.93kcalmol−1 but the downhill potential energy surface discloses that each step of the cyclopropanation reaction are all irreversible. Thus, nickel(0) catalyzed cyclopropanation reaction proceed easer than nickel(II). [Copyright &y& Elsevier]

Abstract: The mechanism for the ion–molecule reaction of benzene anion with nitrous oxide has been characterized using the second-order Møller–Plesset perturbation theory (MP2). All the stationary points were determined at the MP2/6-31++G(d,p) level of the theory. As a result, our theoretical investigations strongly suggest that the main pathways on the potential energy surface can be pathways 1 and 2 of the Channel 1 which are two reciprocally competitive pathways, the minor ones can be expressed as pathway (Channel 1) 3 and Channel 2, and Channel 3 should be a competitive reactive pathway relative to the main reactive pathways. Theoretical calculated results are basically consistent with the experimental postulate. Furthermore, some specific character of the reaction of with N2O has been educed by the mechanism study. [Copyright &y& Elsevier]

Abstract: The cyclopropanation reaction of ethene with aluminum carbenoid has been studied by means of the B3LYP hybrid density functional method. The reaction goes through two pathways: methylene transfer and carbometalation. In methylene transfer pathway, a quantum-chemical investigation shows that the reactions of the carbenoids X2AlCH2X 1-X, (X=F, Cl, Br, I) with ethene 2 to cyclopropane 3+lX3 profit from a weakening of the C–X bonds by the C–Al bonds in the carbenoids 1-X and in the complex [1-X∗2]. The C–F bond is more affected than the C–I bond. Since in the transition states 3[1-X∗2]‡ AlHal is strongly decomplexed, the cleavage of the C–Hal bond is essential compensated by the formation of the Al–Hal bonds, which leads to almost equal transition state energy for the reactions of 1-X with 2. In contrast with methylene transfer, the cyclopropanation reaction of the carbometalation pathway profit from a weakening of the C–Al bonds by the C–X bonds. [Copyright &y& Elsevier]

Abstract: The gas-phase reactions of fluorocarbon compounds CH4– n F n (n =1–3) with Pt (3D, 1S) have been systematically explored via density functional theory (DFT) in order to investigate the mechanisms of these reactions. The results indicate that a reaction of CH3F with Pt (3D, 1S) experiences a rearrangement process to generate counterintuitive production (CH2F−PtH). CH2F2 and CHF3 activation by Pt (3D, 1S) yields high-oxidation-state complexes with carbon–metal double bonds. Moreover, the attack of platinum atoms on fluorine atoms in different fluorocarbon compounds involves intersystem crossing (ISC) between triplet and singlet state Potential Energy Surfaces (PESs). The crossing points (CPs) have been located by the intrinsic reaction coordinate (IRC) approach used by Yoshizawa et al. and corresponding minimum energy crossing points (MECPs) obtained by the mathematical algorithm proposed by Harvey et al. have also been used. Additionally, possible spin inversion processes are discussed using spin–orbit coupling (SOC) calculations. [ABSTRACT FROM AUTHOR]

Abstract: Activation of the N–N and N–O bonds by La+ in nitrous oxide has been examined systematically using both DFT and CCSD(T) methods. The calculated results indicate that the reaction of La+ (3F, 1D) with N2O (X 1∑) including several reaction pathways and numerous isomers, leads to oxidation, LaO+ (1∑, 3Δ)+N2 () or nitration, LaN+ (2∑+, 4∑+)+NO (X 1∏). The attack of the La+ on the O-end of N2O involves intersystem crossing (ISC) between singlet and triplet state potential-energy surfaces (PESs). Thus, possible spin-inversion process is discussed by means of spin–orbit coupling (SOC) calculations. The probability values of the single () and double () passes are estimated at MECP are approximately 6.682×10−2 and 0.125, respectively. The calculated results also revealed that the O-transfer reaction is energetically more favorable than the N-transfer reaction on the both spin state PESs. These results are in good agreement with experimental observations. [Copyright &y& Elsevier]

Abstract: A systematic theoretical study of the reaction NO2(2A1)+CO(1∑+)→NO(2∏)+CO2(1∑g +) catalyzed by Ti+ has been investigated by means of UB3LYP/6-311+G(2d) level. Our calculated results sharply reveal that both NO2(2A1)+Ti+(X4F)→NO(2∏)+TiO+(X2Δ) and TiO+(X2Δ)+CO(1∑+)→Ti+(X4F) + CO2(1∑g +) are spin-forbidden reactions. The minimum-energy crossing points (MECPs) that are involved have been characterized at the same level and the possible spin inversion processes are discussed using the intrinsic reaction coordinate (IRC) approach. [Copyright &y& Elsevier]

Abstract: Calculations based on density functional theory (DFT) have been carried out to investigate geometries and bonding characteristics of all the stationary points associated with the gas-phase ion/molecule reactions of YNH+ (1∑+) with propene. The potential energy surface (PES), including six reaction pathways (four dehydrogenation and two demethanation processes), has been explored and analyzed. By contrast, dehydrogenation reaction channels that are associated with two consecutive hydrogen transfers from C atoms of propene fragment to Y atom of YNH+ moiety and then elimination of H2, are energetically favorable, which is in good agreement with the experimental observation. [Copyright &y& Elsevier]

Abstract: The entire reaction mechanism for the gas phase CO–CO2 conversion by FeO+ is discussed by means of the density functional theory and the intrinsic reaction coordinate approach. The calculated results have strongly indicated that the reaction of is a spin-forbidden reaction between the quartet and the sextet potential energy surfaces (PESs). There is a crossing point between the quartet and the sextet potential energy surfaces which may play a significant role in this reaction, by which the activation energy can be decreased from −15.1 to −56.4kJmol−1 at the reaction system. [Copyright &y& Elsevier]

Abstract: The reaction pathway and energies for the gas-phase CO2–CO conversion by W+ are discussed from density functional theory (DFT) UB3LYP calculation at the relativistic effective core potential (ECP) of Stuttgart basis sets with W+ and 6-311+G(2d) with CO2. The reaction mechanism between W+ and CO2 is an insertion–elimination mechanism. The W+ inserts with no energy barrier into a CO bond resulting in an OWCO+ insertion product. The intrinsic reaction coordinate for the insertion process has been defined and the reaction mechanism has been investigated by analyzing various structures along this path. Crossing points (CPs) are localized, and possible spin inversion processes are discussed by means of the intrinsic reaction coordinate (IRC) approach. [Copyright &y& Elsevier]

Abstract: The reaction of La+ with CH3F, which was selected as a representative system of the activation of C–F bond in fluorohydrocarbons by bare lanthanide cations, has been examined using density functional theory (DFT) to explore more integrated reaction pathways and mechanisms on both singlet and triplet potential energy surfaces (PESs). A direct fluorine abstraction mechanism and an insertion–elimination mechanism were revealed, the related thermochemistry data involved in reaction of La++CH3F were determined. The crossing points (CPs) have been found by means of single-point computations as a function of the structural change along the intrinsic reaction coordinate (IRC) in this manuscript. The present results not only support the existing reaction conclusions inferred from early experimental data, but also complement the pathway and mechanism for this reaction, which can act as a guide for further experimental researches and theoretical investigations. [Copyright &y& Elsevier]

Abstract: The mechanisms for the abstraction reactions of germylenes with oxirane and thiirane have been characterized in detail using density functional theory. All the stationary points were determined at the B3LYP/6-311++G (d, p) level of the theory. As a result, our theoretical investigations suggest that, irrespective of deoxygenation and desulfurization, the alkyl-substituted germylene abstractions are much more favorable than those of the π-donor-substituted germylenes. Moreover, for a given germylene, the desulfurization reaction is more exothermic as well as more kinetically favorable. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. A comparison with carbene and silylene also led to the same result and the results obtained allowed a number of predictions to be made. [Copyright &y& Elsevier]

Abstract: The reactivity of X(3P) (X=Ge, Sn, Pb) with N2O(X1Σ) on both singlet and triplet potential energy surfaces have been investigated at the B3LYP level of theory. To accurately evaluate the activation barrier and reaction energy, the coupled cluster single point calculations using the B3LYP structures is performed. The calculated results are in good agreement with experimental observations. The (X=Ge, Sn, and Pb) reactions that Arthur Fontijn has been observed are spin-forbidden for formation of ground state products in the experiments. The present paper is discussed with the aid of the direct abstraction (DA) mechanism (also called the surface crossing model), a correlation argument based on separated fragments X+O+N2 can explain the inefficiency of the (X=Ge, Sn, and Pb) reactions at 298K by the need to switch electron configurations along low-energy adiabatic paths from ground-state reactants to energetically accessible product states. [Copyright &y& Elsevier]