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Abstract: The singlet potential energy surface of the CF3O+NO reaction has been studied at the B3LYP/6-311+G(3df) level of theory. The relative energies were calculated by using the CCSD(T)/aug-cc-pVDZ and the G3B3 methods at the B3LYP/6-311+G(3df) optimized geometries. The study shows that the reaction starts via an exothermic barrierless addition of NO to the CF3O radical to produce cis-CF3ONO, which will isomerize to trans-CF3ONO, followed by trans-CF3ONO dissociating to the products CF2O+FNO. trans-CF3ONO can also rearrange to trans-CF3OON and further isomerize to cis-CF3OON. Once cis-CF3OON is formed, it will finally dissociate to CF2O+FNO. This is another energetically facile reaction route to produce CF2O+FNO. The transition states involved in above reaction pathways all lie below the reactants in energy, thus the present calculations suggest the overall rate coefficient of the title reaction may exhibit a negative temperature dependence, in agreement with most experimental results. Additionally, the enthalpies of formation of CF3NO2, trans-CF3ONO and cis-CF3ONO were computed to be =−160.99kcal/mol, =−176.76kcal/mol and =−173.24kcal/mol, respectively. [Copyright &y& Elsevier]

Abstract: The reaction mechanism of CCN with H2S has been studied by using the method of hybrid density functional B3LYP at the 6-311+G(2d,p) basis set. The transition state of each reaction is verified via the analysis of vibration mode and intrinsic reaction coordinate (IRC). Meanwhile, single-point energy has been calculated at the CCSD(T)/6-311+G(2df,p) and G3B3 level, and the zero-point energy correction has been made to the total energy and reaction energy barrier. For comparison, the reaction of CCN+H2O has also been calculated by the same method. The calculation reveals, for the CCN+H2X (X=S, O), a mechanism of carbyne insertion–dissociation. The most feasible reaction channels are CCN+H2X→H2XCCN (1)→HXC(H)CN (2a)→H+XCHCN (P5) and CCN+H2X→H2XCCN (1)→HXC(H)CN (2a)→HXC(H)CN (2b)→XCH2CN (6)→H+XCHCN (P5), and they both give the dominate products H+XCHCN. [Copyright &y& Elsevier]

Abstract: The reaction pathways of sulfur vapor with ozone on the singlet potential energy surface have been investigated theoretically at CCSD(T)/6-311++G(3df,3pd)//B3LYP/6-311++G(3df,3pd) level of computation. The calculated results show that the reactants are initially associated with the adduct S–O3 through a barrierless process. Subsequently, via a variety of transformations of isomer S–O3, two kinds of products P1(SO+ 3O2) and P2(SO3(D3h)) are obtained. The cleavage and formation of the chemical bonds in the reaction pathways have been discussed using the topological analysis of electronic density. The topological analysis results show that the ring transitional structure region occurs in cis-OSOO→SO3(Cs) and SO3(Cs)→SO3(D3h) reaction pathways. [Copyright &y& Elsevier]

Abstract: The potential energy surface of K+·CO2 and K+·CS2 complexes are determined at high levels of ab initio theory (CCSD), B3LYP, and MP2 using different basis sets. These calculations predict the existence of three minima for K+·CO2 complex; linear, quadrilateral and Y-shape, and two minima for K+·CS2 complex; bent and Y-shape. In addition, the binding energies, and other thermodynamic quantities are calculated at different levels of theories. Our calculations show that the difference in the global minima geometries of both complexes is mainly due to the sign of the quadrupole moment of CO2 and CS2 molecules. [Copyright &y& Elsevier]

Abstract: The detailed singlet potential energy surface (PES) of the [FNO3] system is investigated at B3LYP/6-311+G(2d) and CCSD(T)/6-311+G(2d) (single-point) levels. Six isomers and nine transition states are located. Various possible isomerization and dissociation channels are probed in order to explore the reaction mechanism for FO2 +NO. The calculated results indicate that the initial association between FO2 and NO can lead to the adduct FOONO, followed by the concerted F-shift and cleavage of the ON bond leading to the dominant product FNO+O2. The formation of other products, however, is much less feasible due to energy constraints. The three feasible products and reaction pathways are also analyzed for another reaction, FO+NO2, on the basis of the [FNO3] PES. This study may be helpful in understanding the reaction and chemical behaviors of oxygen fluorides. [Copyright &y& Elsevier]

Abstract: The proton affinities (PAs) and potential energy surfaces (PESs) of hydrochlorofluoromethanes (HCFMs) have been predicted by using Gaussian-3X (G3X) method. The G3X PAs agree with previous G3 predictions, while the large discrepancies between theoretical and experimental PAs persisted for CH2F2, CHF3, and CF3Cl. Protonated HCFMs usually have multiple structures, and structures with protonations at F-atom, [Methyl-FH]+, are the most stable. Transition states connecting different cation structures have been identified as proton exchanges between C–H σ-bonds or between halogen atoms. While the high transition barriers hinder the isomerization between different cation structures, protonated HCFMs from proton transfer reactions of HCFMs with HCFM+/HCO+/HN2 + may have high enough energy to decompose to methyl+ +HF/HCl or isomerize to less stable structures. Under low collision energy condition, reactions of methyl+ and H2/HF/HCl form ion complexes only, except for CH3 + +HCl, where CH2Cl+ +H2 can be formed by crossing over the transition barrier from [CH3–ClH]+ to [CH2Cl–H2]+. [Copyright &y& Elsevier]

Abstract: The structures, energetics, spectroscopies, and stabilities of the doublet Si2PS radical are explored at the density functional theory and ab initio levels. Fifteen minima including the chainlike, three-membered ring, four-membered ring, and cagelike structures are located connected by 24 interconversion transition states. The structures of the stable isomers and their relevant transition states are further optimized at the QCISD/6-311G(2d) level. At the CCSD(T)/6-311+G(2df)//DFT/B3LYP/6-311G(d)+ZPVE level, the global minimum is found to be a four-membered-ring cPSiSSi 10 (0.0kcal/mol) with a 2A′′ electronic state, whereas the cagelike isomer cagePSiSiS 15 (3.5kcal/mol), the three-membered-ring isomers S-cSiPSi 4 (12.1kcal/mol), and P-cSiSiS 5 (27.6kcal/mol) also possess considerable kinetic stabilities (more than 10.0kcal/mol). The bonding natures and structures of the four isomers 4, 5, 10, and 15 are analyzed. The calculated results are compared with those of the analogous molecules C2PS and SiCPS. [Copyright &y& Elsevier]

Abstract: The potential energy surface for the reaction of the CF3O radicals with CO was investigated. The geometries and vibrational frequencies of the reactants, transition states, intermediates, and products were calculated at the UB3LYP/6-311+G(2d,p), UB3LYP/6-311+G(3df,2p) and UMP2/6-311+G(2d,p) levels of theory. The energies were improved by using the G2M(CC2) and G3B3 methods. The calculation suggests the reaction proceeds via either the fluorine abstraction of CF3O by CO to produce FCO+CF2O with a high energy barrier or the barrierless association of the reactants to form the trans-CF3OCO intermediate. The trans-CF3OCO is predicted to undergo subsequent isomerization to cis-CF3OCO or dissociate directly to the products FCO+CF2O and CF3 +CO2. The collisional stabilization of trans-CF3OCO is dominant at room temperature, while trans-CF3OCO isomerizing to cis-CF3OCO followed by dissociating to CF3 +CO2 is accessible when temperature rises. The reason for only trans-CF3OCO without cis-CF3OCO observable in Ashen’s experiment [S.V. Ahsen, J. Hufen, H. Willner, J.S. Francisco, Chem. Eur. J. 8 (2002) 1189] is cis-CF3OCO can be produced only via the isomerization of trans-CF3OCO, and its yield is inappreciable at a low experimental temperature. The enthalpies of formation for the two conformations of CF3OCO have been deduced: (trans-CF3OCO)=−196.25kcalmol−1, (trans-CF3OCO)=−197.46kcalmol−1, (cis-CF3OCO)=−193.64kcalmol−1, and (cis-CF3OCO)=−194.90kcalmol−1. [Copyright &y& Elsevier]

Abstract: The potential energy surfaces for the La+CO2 and La+ +CO2 reactions have been theoretically investigated by using the DFT (B3LYP/ECP/6–311+G(2d)) level of theory. To obtain an accurate evaluation of the activation barrier and reaction energy, the QCISD(T) single-point calculations using the B3LYP structures were performed. Both ground and excited state potential energy surfaces are discussed. These results show that the reaction mechanism is insertion mechanism along the C–O bond activation branch. The reaction of La atom with CO2 was shown to occur preferentially on the ground state (doublet) PES throughout the reaction process, and the experimentally observed species, has been explained according to the mechanisms revealed in this work. As for the reaction between La+ cation with CO2, it involves potential energy curve-crossing which dramatically affects reaction mechanism, and the crossing points (CPs) have been localized by the approach suggested by Yoshizawa et al. Due to the intersystem crossing existing in the reaction process of La+ with CO2, the intermediate (OLa(η 2-CO))+ may not form. This mechanism is different from that of La+CO2 system. All our theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction. [Copyright &y& Elsevier]

Abstract: Density functional theory (DFT) calculations have been performed to explore the sextet, quartet, and doublet potential energy surfaces of C–X (X=S, O) bond activation in CS2 and SCO molecules by gas-phase Mo+ cation, in order to better understanding the reaction mechanism of second-row metal cations reacting with SCX (X=S, O). The minimum energy reaction path is found to involve the spin inversion in the different reaction steps. The crossing points (CPs) of the different potential energy surfaces (PESs) have been localized with the approach suggested by Yoshizawa et al. [K. Yoshizawa, Y. Shiota, T. Yamabe, J. Chem. Phys. 111 (1999) 538]. The potential energy curve-crossing dramatically affects reaction mechanism. The present results show that the reaction mechanism is insertion–elimination mechanism both along the C–S and C–O bond activation branches, but the C–S bond activation is much more favorable than the C–O bond activation in energy. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction. [Copyright &y& Elsevier]

Abstract: This study investigates the interaction between C70 and X (X=H and F), and the potential energy surface of C70X radical. Our findings show that there are five distinct isomers of C70X on the surface. The calculations on the structures and energies are further discussed thermodynamically using the density function theory method at the B3LYP/6-31G (d) level. In addition, the transition states, as well as reaction pathways of X (X=H and F) transferring between different key points on C70 representative patch, are given to explore the possible reaction mechanism. Finally, the stability of C70X2 is discussed through the density functional theory. [Copyright &y& Elsevier]

Abstract: The reaction of isocyanato radical, NCO (X2∏) with chlorine atom, Cl (2Pu) is investigated by ab initio quantum chemistry methods. The important triplet potential energy surfaces (PES) are calculated at the CCSD(T)/aug-cc-pVQZ//CCSD/6-311++G∗∗+ZPE levels. On the triplet PES of the title reaction, the most possible pathway is via 3TSR-1 forming the cis isomer 31, and then 31 can lead to the lower trans isomer 32 via transition state 3TS1-2, followed by the transition state 3TS2-P1 to get the important product P1 with larger exothermic. The other reaction pathways are less competitive due to thermodynamical or kinetic factors. The possible singlet–triplet intersystem crossing is also discussed. We expect this contribution can lead us to deeply understand the mechanism of the title reaction and may be helpful for the modeling of isocyanato radical-halogen combustion chemistry. [Copyright &y& Elsevier]

Abstract: The low-energy structures and internal rotation about the C1- bridging bond of rac-6,6′,7,7′-tetramethoxy-1,1′,2,2′,3,3′,4,4′-octahydro-1,1′-bisisoquinoline, its N-alkyl and N-acyl derivatives were studied using the DFT B3LYP method. The global minimum (gauche) of 1,1′-bisisoquinoline was found to be different from the reported crystal structure (trans), which indicated the important of environment on the compound conformation and hence it catalytic potential. Our calculations also indicated that the global minima of 1,1′-bisisoquinoline and its derivatives are dynamically stable along their internal rotation potential energy surface. The stable conformations of the tetrahydroisoquinoline groups of N-acyl derivatives are different from their parent molecule and there is a dependency of their structures on the N-substituents for N-acyl derivative. [Copyright &y& Elsevier]

Abstract: Ab initio calculations have been carried out for the weakly bound cluster of nitrogen and benzene and for the isoelectronic cluster of acetylene and benzene. With nitrogen and acetylene having quadrupole moments of opposite sign, their energetically preferred orientation with respect to benzene differs, with N2 parallel and acetylene perpendicular to the benzene plane. The interaction surface for the N2–benzene dimer reveals that there is little potential energy change for rotation of N2 about an axis perpendicular to the benzene plane and little change for considerable displacement away from its equilibrium position above the center of the benzene ring. Hence, this unique potential surface is suggestive of free rotation by N2 (a spinning top) along with significant ground vibrational state displacement across the surface of benzene leading to a symmetrically tethered N2. [Copyright &y& Elsevier]

Abstract: A three-dimensional potential energy surface of the electronic ground state HXeI is constructed from more than 4200 ab initio points at the internally contracted multi-reference configuration interaction with the Davidson correction (icMRCI+Q) level employing large basis sets. The calculations indicate that the linear HXeI molecule is metastable with a barrier of 0.365eV in the atomization (HXeI→H+Xe+I) channel and a barrier of 1.306eV in the dissociation (HXeI→HI+Xe) channel. Low-lying vibrational energy levels of both HXeI and DXeI are calculated on the three-dimensional potential energy surface using the Lanczos algorithm, and found to be in good agreement with known experimental band origins. [Copyright &y& Elsevier]

Density functional study of the reaction of Sn(OCH2CH2NMe2)2 (1) with Me3Si–N3 (2) yielding the redistribution product [(N3)SnOCH2CH2NMe2]2 (3) has been performed at the PBE/TZ2P(SBKJC) level. Two possible reaction paths, the formation of [(N3)SnOCH2CH2NMe2]2 (path A) and initially expected imine Me3Si–N=Sn(OCH2CH2NMe2)2 (5) (path B), have been studied. The formation of the imine 5 is thermally more favorable than the formation of dimeric stannylene 3, ΔG0(5) = −6.7 kcal/mol and ΔG0(3) = −5.9 kcal/mol. The reaction proceeds to 3 due to a lower energy barrier, ΔG‡ = 27.8 and 39.5 kcal/mol for 3 and 5, respectively. [Copyright &y& Elsevier]

Abstract: The cycloaddition mechanism of forming a silapolycyclic compound between singlet dimethylmethylenesilylene and acetone has been investigated with MP2/6-31G∗ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated with CCSD(T)/6-31G∗//MP2/6-31G∗ method. From the potential energy profile, we predict that the cycloaddition reaction has two competitive dominant channels of forming a silapolycyclic compound. Both channels consist of four steps: (I) the two reactants first form three-membered ring intermediate and twisted four-membered ring intermediate through a barrier-free exothermic reactions of ΔE =−0.1 and −10.7kJmol−1; (II) the three-membered ring intermediate and twisted four-membered ring intermediate then isomerize to two plane four-membered ring products via transition states with energy barriers of 3.4 and 6.5kJmol−1; (III) the two plane four-membered ring products further react with acetone(R2) and form intermediates, which are also barrier-free exothermic reactions of ΔE =−38.9 and −64.8kJmol−1; (IV) the two intermediates isomerize to silapolycyclic compounds via transition states with energy barriers of 41.8 and 45.9kJmol−1, respectively. [Copyright &y& Elsevier]

Abstract: The structures, energetics, spectral parameters and stability of the singlet SiCP2 isomers are explored at the density functional theory and ab initio levels. Eight isomers connected by ten interconversion transition states are located at the CCSD(T)/6-311G(2d)//B3LYP/6-311G(d)level. The kinetically stable isomers and their relevant interconversion transition states are further refined at CCSD(T)/6-311+G(2df)//QCISD/6-311G(d) level. At QCISD/6-311G(d) level, one four-membered ring isomer cSiPCP and two linear structures PSiCP, SiCPP possess considerable kinetic stability (more than 15kcal/mol). The valence bond structures of three kinetically stable SiCP2 isomers are analyzed. The similarities and discrepancies in structure, energy and stability between SiCP2 and its analogous C2P2, Si2P2, SiCN2 and CSiNP molecules are also discussed. The predicted structures and spectroscopic properties are expected to be informative for the identification of the SiCP2 in the laboratory and space. [Copyright &y& Elsevier]

Abstract: The reaction of CN with HONO is explored theoretically using coupled cluster and Møller–Plesset perturbation theory. Various possible reaction pathways including the H-abstraction reactions and addition–isomerization–elimination reactions are considered. Because the rate-determining barrier in the most feasible pathway lies −4.92/−30.58kcal/mol (ΔE ‡/ΔG ‡) lower than reactants, the reaction is expected to be very rapid. Based on the analysis of the temperature influence of the reaction mechanism, we expect that the actual reaction mechanism may vary with experimental conditions. We expect this contribution can lead us to deeply understand the mechanism of the title reaction. [Copyright &y& Elsevier]

Abstract: The mechanism of the cycloaddition reaction between singlet silylene carbene and formaldehyde has been investigated with MP2/6-31G∗ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6-31G∗ method. From the potential energy profile, it can be predicted that the two competitive dominant reaction pathways of the cycloadditional reaction between singlet silylene carbene and formaldehyde are reaction 4 and reaction 5. Reaction 4 consists of three steps: the two reactants (R1, R2) firstly form a twist four- membered ring intermediate INT4 through a barrier-free exothermic reaction, this intermediate INT4 then isomerizes to a four-membered ring compound P4 via a transition state TS4. subsequently, the compound P4 isomerizes to product P4.2 via a transition state TS4.2, which results from the hydrogen transfer. The process of reaction 5 is as following: on the basis of P4 formed from the reaction 4 between R1 and R2, P4 further reacts with formaldehyde (R2) to form the intermediate INT5 through a barrier-free exothermic reaction, then INT5 isomerizes to a silicic bis-heterocyclic compound P5 via a transition state TS5. [Copyright &y& Elsevier]

Abstract: Mechanisms of cycloaddition reaction between singlet dimethyl methylene carbene and ethylene has been investigated with MP2/6-31G∗ method, including geometry optimization and vibrational analysis. Energies for the involved stationary points on the potential energy surface are corrected by zero-point energy and CCSD(T)//MP2/6-31G∗ single-point calculations. From the potential energy surface obtained with the CCSD(T)//MP2/6-31G∗ method for the cycloaddition reaction between singlet dimethyl methylene carbene and ethylene, it can be predicted that reactions (1) and (3) should be two competitive leading channels of cycloaddition reaction between them. The former consists of two steps: (I) the two reactants firstly form an energy-rich intermediate, INT1, which is a barrier-free exothermic reaction; (II) the intermediate INT1 isomerizes to a three-membered ring product P1 via a transition state TS1. The latter proceeds in three steps: (I) the two reactants firstly form a four-membered ring intermediate, INT2, through a barrier-free exothermic reaction; (II) the intermediate INT2 further reacts with ethylene (R2) to form an intermediate, INT3, which is also a barrier-free exothermic reaction; (III) INT3 isomerizes to a polycyclic product P3 via a transition state TS3. [Copyright &y& Elsevier]

Abstract: Rare-gas clusters are usually modeled by Lennard–Jones pairwise potential energy functions. A more realistic representation of the rare-gas pair interaction is given by the benchmark Aziz HFD type potentials, of high computational cost for large scale molecular simulations. Here we compare Lennard–Jones and HFD potentials with that obtained from a generalization of the Lennard–Jones potential, recently presented by Pirani et al. Parameters are given for the two-body interaction for all dimers and structural properties of Ar5 and Ar6 are discussed through a comparison of the Pirani et al. potentials with those of Lennard–Jones. [Copyright &y& Elsevier]

Dehydroamino acids with a methylated N-terminal tertiary amide bond occur in natural small cyclic peptide toxins. To investigate their conformational preferences a systematic theoretical analysis was performed on N′-methylamides of N-acetyl-N-methyldehydroamino acids (Ac-Δ(Me)Xaa-NHMe, where Xaa = (Z)-Abu, (E)-Abu, Val, (Z)-Phe, and (E)-Phe) considering the configuration trans and cis of the tertiary amide bond. The ϕ, ψ potential energy surfaces were calculated at the B3LYP/6-31+G∗∗//HF/3-21G level with inclusion of the solvent (water) effect (SCRF method). The conformers localised were fully optimised at the B3LYP/6-31+G∗∗ in vacuo. The accessible areas of the potential energy surfaces; the number of conformers and the stabilising internal forces were compared for all the studied molecules. The main feature of the studied N-methyldehydroamino acids is their considerable tendency to adopt the configuration cis for the N-terminal tertiary amide bond. It results from the specific ability of these dehydroamino acids to be able to gain stability from the π-electron conjugation between the Cα=Cβ double bond and the neighbouring C-terminal amide group. This stabilising force concomitant with the short N—H⋯N hydrogen bond makes the conformer cis C7eq (φ, ψ ∼ −105°, 8°) the lowest in energy. The data presented hereinto indicates that N-methyldehydroamino acids can potentially be new promoters of trans–cis isomerisation of the amide bond. [Copyright &y& Elsevier]

Abstract: The reaction of OH radical with nitrous acid HONO is investigated by ab initio quantum chemistry methods. The doublet potential energy surfaces are calculated at the CCSD(T)/aug-cc-pVDZ//UMP2/6-311++G(d,p) levels. Various possible reaction pathways are considered. Among them, the most feasible pathway should be the OH radical attacking on the hydrogen of cis-HONO to form a 6-member-ring complex C2 barrierlessly, followed by the indirect hydrogen abstraction transition state TSabsC2-C6I to form a weakly bound complex C6, giving rise to the educts P1 H2O+NO2. Because all of the complexes, transition state, and products involved in the feasible pathway lie below the reactants, the title reaction is expected to be rapid, which in good agreement experiment. The present study may be helpful for probing the mechanisms of the HONO reactions and understanding the atmospheric chemistry. [Copyright &y& Elsevier]

Abstract: The mechanism of the cycloaddition reaction of forming a silapolycyclic compound between singlet methylenesilylene and ethene has been investigated with the MP2/6-31G∗ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by the CCSD(T)//MP2/6-31G∗ method. From the potential energy profile, it can be predicted that, reaction (3) is the dominant channel of cycloaddition reaction between singlet methylenesilylene and ethene. This reaction consists of four steps: (I) the two reactants first form a three-membered ring intermediate INT through a barrier-free exothermic reaction of 13.3kJmol−1; (II) INT then isomerizes to a four-membered ring product P2 via the transition state TS2 with an energy barrier of 32.0kJmol−1; (III) P2 further reacts with ethene(R2) to form a silapolycyclic intermediate INT3, which is also a barrier-free exothermic reaction of 11.8kJmol−1; (IV) INT3 isomerizes to a silapolycyclic compound P3 via the transition state TS3 with an energy barrier of 1.5kJmol−1. This reaction has quite excellent selectivity. [Copyright &y& Elsevier]

Abstract: The qualitative molecular orbital approach based on orbital interactions was used to explore the nature of bonding in cyclic fluorophosphazenes (F2PN) n , where n is 2–6. Besides the classical skeleton of σ-bonds, only two, one radial and one axial, 2n-center two-electron π-bonds significantly participate in the extra stabilization of the (PN) n ring. The π-radial interaction is more effective and comparable by size with the σ ones. Additional slight stabilization of a (PN) n ring is achieved by nonbonding π-radial and π-axial molecular orbitals (MOs) which are mainly localized on nitrogen atoms. The orbital interactions have a hyperconjugation character. The bonding energy decomposition analysis showed that the cyclic interactions are about half covalent and half electrostatic. The covalent bonding is dominated by radial interactions. The aromaticity concept is not appropriate for description of bonding in cyclophosphazenes. The contribution of phosphorus d atomic orbitals to the concept of chemical bonding in phosphazenes is negligible, but the inclusion of d phosphorus functions in a basis set is appropriate for a correct quantitative description of electronic and geometric structure. Extended Hückel (EHT), ab initio and density functional (DFT) calculations provide the same qualitative picture of the bonding. The very flat B3LYP/6-311+G(3df)//B3LYP/6-31G(3df) potential energy surface (PES) with the low energy barrier (∼1.6kJmol−1) indicates the very fast and easy conformational motion of (F2PN)4. The global minimum on this PES is the S 4 conformation. [Copyright &y& Elsevier]

Abstract: The potential energy surface (PES) of CN2H rotation of the encapsulated 1-bicyclo[2.2.1]heptyldiazirine (BHD) inside a molecular container: Cram’s hemicarcerand (CH) was explored using two different DFT involved ONIOM methods: B3LYP/6-31G∗∗//ONIOM(B3LYP/6-31G∗: AM1) and B971/6-31G∗∗//ONIOM(B971/6-31G∗: AM1). The free-state PES of CN2H rotation was also calculated, respectively by B3LYP/6-31G∗∗//B3LYP/6-31G∗ and B971/6-31G∗∗//B971/6-31G∗ methods for comparison. The findings in this study have shown that the PES profiles differ from each other notably in the two states. In the encapsulated state the rotation barrier corresponding to the free-state conversion with the largest rotation barrier increases by about 2kcal/mol, which has exceeded the largest rotation barrier in the free-state. The conformational preference behavior towards certain BHD isomers, which might be in better conformational compatibility with the container, has been demonstrated. [Copyright &y& Elsevier]

Abstract: The reactivity of Ni+ with OCS on both doublet and quartet potential energy surfaces (PES) has been investigated at the B3LYP/6-311+G(d) level. The object of this investigation was the elucidation of the reaction mechanism. The calculated results indicated that both the Ce:glyph name="sbnd" />O bond activations proceed via an insertion–elimination mechanism. Intersystem crossing between the doublet and quartet surfaces may occur along both the Ce:glyph name="sbnd" />O bond activation branches. The ground states of NiS+ and NiO+ were found to be quartets, whereas NiCO+ and NiCS+ have doublet ground states. The Ctivation is energetically much more favorable than the Ctivation. All theoretical results are in line with early experiments. [Copyright &y& Elsevier]

Abstract: In order to study the structural and electronic properties of endohedral fullerene Be@C70, semi-empirical AM1, PM3, and density functional theory at B3LYP level and MP2 method were utilized to optimize the geometry and calculate the potential energy surface, LUMO–HOMO, electron affinity, ionization potential and Mulliken population. The results show that a Be atom is located at the center of a fullerene cage and nearly keeps its electronic configuration, and that the interaction between the Be atom and its fullerene cage was found to be attractive. The calculations also indicate that the central Be atom deforms the C70 fullerene cage slightly, and that the possibilities of both accepting and donating electron of the C70 cage are nearly not affected by the encapsulated Be doping. And also the hybridization between the Be atom and the fullerene cage is slight. [Copyright &y& Elsevier]

Abstract: The radical–molecule reaction between the imino radical (NH(3Σ−)) and C2H4 plays a very important role in atmospheric chemistry. A systematic theoretical study of the reactions of NH(3Σ−) with C2H4 has been carried out. Both the singlet and triplet potential energy surfaces (PESs) for the gas-phase reaction between NH(3Σ−) and C2H4 have been investigated by means of G3B3 and G2M (CC, MP2) levels of theory using the B3LYP/6-31G(d) and B3LYP/6-311++G(3df,2p) geometries, respectively. The minimum energy crossing point (MECP) between the triplet and singlet potential energy surfaces is found with the B3LYP/6-311++G(3df,2p) level. It is revealed that the products of H+CH2CHNH(II) and CH4 +HNC are dominant on the triplet and singlet potential energy surfaces, respectively. [Copyright &y& Elsevier]

Abstract: The complex potential energy surface for the reaction of CH2ClO2 with HO2, including 12 intermediates, 31 interconversion transition states and 16 major dissociation products, was theoretically probed at the G2MP2//B3LYP/6-311G(2d,2p) level of theory. The geometries and relative energies for various stationary points were determined. Based on the calculated G2MP2 potential energy surface, the possible mechanism for the reaction of CH2ClO2 with HO2 was proposed. It is shown that the most feasible channels are those leading to CH2ClOOH+ 3O2, CHClO2 +H2O2, CH2ClOH+O3 and CH2O+ 2Cl+ 2HOOO, with the energy barriers of 17.0, 22.6, 24.5 and 24.5kcal/mol, respectively. Among them, the formations of the first product is a one-step reaction, while the others are produced via CH2ClO2 and HO2 by forming a tetroxide intermediate first, then the intermediate dissociates to yield productions or through multi-steps reactions via several transition states and intermediates to produce the final products. Our results suggest that besides CH2ClOOH+ 3O2, it is also possible for the reaction of CH2ClO2 with HO2 to form the others. In addition, most of the product CH2ClOOH will undergo secondary dissociation to yield HC(O)Cl and H2O via a barrier of 45.9kcal/mol. And the secondary decomposition of the product HOOO gives 2OH and O2 with a small barrier of 3.8kcal/mol. [Copyright &y& Elsevier]

Abstract: In a series of TD-DFT calculations we have investigated the homolytic cleavage of N–Cl and C–Cl bonds in protonated and neutral aliphatic amines on the ground- and excited-state potential energy surfaces. Our focus is to address the possibility of ultrafast bond breakage and the further processes that the resulting N and C based radicals can undergo. The S1 n → σ * states of the N-chloro-amines are repulsive whereas the S1 states of the N-(chloroalkyl)-amines are bound Rydberg states. On the S1 states of the N-chloro-amines the possibility therefore exists for ultrafast formation of N-based radicals. This state is conveniently located for a femtosecond resolved pump-probe study at 266nm. An analysis of the conformers of the resulting radicals shows that – except in the N-protonated δ-alkyl radical – there is no driving force to induce a conformational change in the radicals. The driving force in the N-protonated δ-alkyl radical is most likely an interaction between the N–H bond and the radical site that has been shown to be important in amine radical cations [S. Hammerum, C.B. Nielsen, J. Phys. Chem. A 109 (2005) 12046]. The calculations could be taken to indicate that it is likely for a conformational change to take place in simple aliphatic amines; in this case all of the lowest excited states are Rydberg states and the excited-state amine therefore resembles a ground state radical cation in which the conformational change is believed to occur. [Copyright &y& Elsevier]

Abstract: The Paal–Knorr pyrrole synthesis, which involves the reaction of 1,4-dicarbonyls with amines, is among the most classical methods of heterocyclic pyrrole ring synthesis. The detailed sequence and the nature of the intermediates that occur in the Paal–Knorr reaction mechanism are not well understood. Density functional theory methods have been employed to investigate the nature of the intermediates and transition states in the Paal–Knorr pyrrole mechanism. Two mechanistic pathways for the reaction were examined: hemiaminal cyclization vs. enamine cyclization. Our calculated reaction potential energy surfaces suggest that the hemiaminal cyclization is the preferred pathway for the reaction both in gas phase and in solution. This conclusion is consistent with the experimental results which suggest that the hemiaminal intermediate undergoes cyclization in the rate-limiting step in the Paal–Knorr reaction mechanism. The preferred mechanism for the Paal–Knorr reaction consists of hemiaminal formation, hemiaminal cyclization and a dehydration step to form the pyrrole ring. Water and hydrogen-bonding interactions play a key role in catalyzing the hydrogen-transfer steps of the reaction. [Copyright &y& Elsevier]

Abstract: The reactivity of Cu+ with OCS on both singlet and triplet potential energy surfaces (PES) has been investigated at the UB3LYP/6-311+G(d) level. The object of this investigation was the elucidation of the reaction mechanism. The calculated results indicated that both the C–S and C–O bond activations proceed via an insertion–elimination mechanism. Intersystem crossing between the singlet and triplet surfaces may occur along both the C–S and C–O bond activation branches. The ground states of CuS+ and CuO+ were found to be triplets, whereas CuCO+ and CuCS+ have singlet ground states. The C–S bond activation is energetically much more favorable than the C–O bond activation. All theoretical results are in line with early experiments. [Copyright &y& Elsevier]

Abstract: The quartet and doublet potential energy surfaces for the reaction of Ti+ +SCO have been calculated at the UQCISD(T)/6-311+G*//UB3LYP/6-311+G* level of theory. The present results show that the reaction mechanism is insertion–elimination mechanism both along the C–S and C–O bond activation branches, but the C–S bond activation is much more favorable than the C–O bond activation in energy. The minimum energy reaction path is found to involve the spin inversion in the reaction steps. Specifically, the reaction is most likely to proceed through the following steps: 4Ti+ +SCO→ 4IM1→CP1→ 2IM2→ 2TiS+ +CO. The overall reaction is calculated to be exothermic by 98.2kJ/mol, which is in good agreement with the available experimental results. [Copyright &y& Elsevier]

Abstract: In this work, the stable conformation and thermal isomerization of p-aminoazobenzene (AAB) were investigated by using ab initial MP2/6-31+G∗ and DFT-B3LYP/6-31+G∗ calculations. For comparison reason, corresponding results of azobenzene (AB) were also obtained by the same theoretical methods. Compared with AB, the MP2 optimized geometries of AAB show little variation in the NN bond length and most bond angles, but show obvious variations in the CN bond length and CCNN dihedral angle that link with the NH2-substituted phenyl ring. Phenyl ring twist of both AB and AAB show two equivalent nonplanar minima in the potential energy surface (PES) of the NNCC dihedral angles, but the potential energy barriers at 0° (the planar structure) are low. For AAB, the energy barrier is even lower for CCNN dihedral angle of the NH2-substituted phenyl ring. The S0 PES of AB obtained by DFT method shows that the energy barrier for CNN inversion is lower than that for CNNC rotation. On the contrary, the energy barriers for AAB along both rotation and inversion pathways are almost equal. Calculation indicates that the molecular structures at the highest points on the PESs of CNNC rotation and CNN inversion of the unsubstituted phenyl ring are identical. On the basis of the calculation, it is believed that even the relative stability of trans- and cis-isomers is not obviously affected by the donor substitution, the thermal isomerization of AAB can go through both the inversion and rotation pathways. [Copyright &y& Elsevier]

Abstract: In an attempt to understand the mechanism of the reaction of azide radical with nitrogen dioxide, the singlet and triplet potential energy surfaces (PESs) for the gas-phase reaction between N3 and NO2 have been investigated by means of G3B3, CBS-QB3, and G2M(CC, MP2) levels of theory. All the pathways on the singlet PES consist of the barrierless formation of a complex as the first reaction step, followed by isomerization and dissociation to the products. Furthermore, the minimum energy crossing point (MECP) between the singlet and triplet potential energy surfaces is found with the B3LYP/6-311++G(d,p) level. The products 2NO+N2 are found to be major and predominant on both the singlet energy surface and the triplet energy surface, whereas 2N2O are expected to be minor products. [Copyright &y& Elsevier]

Abstract: In order to elucidate the mechanism of reaction M+ +SCO, both triplet and singlet potential energy surfaces (PESs) for the reaction of Sc+ +SCO have been theoretically investigated using the DFT (B3LYP/6-311+G*) level of theory. The geometries for reactants, intermediates, transition states and products were completely optimized. All the transition states were verified by the vibrational analysis and the intrinsic reaction coordinate calculations. The involving potential energy curve-crossing dramatically affects reaction mechanism, reaction rate has been discussed, and the crossing points (CPs) have been localized by the approach suggested by Yoshizawa et al. The present results show that the reaction mechanism are insertion–elimination mechanism both along the C–S and C–O bond activation branches, but the C–S bond activation is much more favorable in energy than the C–O bond activation. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction. [Copyright &y& Elsevier]

Abstract: A systematic theoretical analysis was performed on N-acetyl-l-alanine N′-methylamide (Ac-l-Ala-NHMe) and the analogues methylated on the N-terminus (Ac-l-(Me)Ala-NHMe), C-terminus (Ac-l-Ala-NMe2), and both N/C-termini (Ac-l-(Me)Ala-NMe2), to evaluate the influence of methylation of the amide group on the conformational properties of the affected residues. The ϕ, ψ potential energy surfaces were calculated at the B3LYP/6-31+G**//HF/3-21G level of theory with inclusion of the solvent (water) effect (SCRF method). The conformers localised were fully optimised at the B3LYP/6-31+G** in vacuo. The accessible areas of the potential energy surfaces; the number of conformers and the stabilising internal forces were compared for all the studied molecules. For comparison, data drawn from the Cambridge Crystallographic Data Centre has been presented. The conformational freedom of residue methylated either on the N-terminal (trans and cis) or C-terminal amide group is reduced, in contrast to residue methylated on both the N/C-terminal amide groups. For all the studied molecules the lowest energy conformers have the methylated amide bond in the trans configuration. NO hydrogen bonds stabilise the lowest conformers of Ac-l-Ala-NMe2 and all the conformers of trans-Ac-l-(Me)Ala-NHMe, but not those of cis-Ac-l-(Me)Ala-NHMe where NN operates. For all the methylated residues studied, the weaker CO hydrogen bonds and the carbonyl C⋯◀Cions seem to play an important role. [Copyright &y& Elsevier]

The structural, spectroscopic and kinetic properties of small molecules composed of second-row elements such as Si and P are vital to understanding the growing process of relevant semiconductors and functional films as well as to predicting new species to be detected in space. In this paper, a detailed computational study is performed on the singlet and triplet [C,Si,N,P] potential energy surfaces at the DFT/B3LYP, QCISD and CCSD(T) (single-point) levels. A total of 38 (15 for singlet and 23 for triplet) minimum isomers and 37 (19 for singlet and 18 for triplet) interconversion transition states are located. Generally, the triplet species lie energetically higher than the singlet ones. At the CCSD(T)/6-311G(2df)//B3LYP/6-311G(d) + ZPVE level, the lowest-lying isomer is SiNCP(1Σ) 11 (0.0 kcal/mol) followed by NCPSi(1A′) 12 (8.9), NCSiP(1Σ) 13 (19.7), PCNSi(1A′) 14 (19.8), CNSiP(1Σ) 15 (26.5), SiCNP 16(1Σ) (31.1) and CNPSi(1A′) 17 (32.2). Except for the isomer 14 with very low isomerization barrier, the remaining six ones have reasonable kinetic stabilities. In addition, although the linear isomers NSiCP 18 (63.8) and SiCPN 110 (73.5) are energetically very high-lying, they contain very large isomerization barriers to allow for existence either in laboratory or in space. By means of structural and bonding analysis, the interesting Si- or P-related triple-bonding are revealed among species like 11 (C≡P), 13 (Si≡P), 15 (Si≡P), 16 (Si≡C, N≡P). Since up to now, stable typical Si≡P and Si≡N triply-bonded species are still experimentally unknown, isomers 11, 13, 15 and 16 may represent such good examples. Moreover, the intramolecular donor–acceptor mechanism from the exocyclic π-bonding to the vacant orbital of one ring-atom is proposed to account for the unique three-membered ring-like structure of the chainlike isomers 12, 14 and 17. Finally, the similarities and discrepancies of CSiNP molecule are compared to the analogous 18-valence-electrons species AA′BB′ (A, A′ are group IV elements and B, B′ are group V elements) such as C2N2, C2NP, CSiN2, Si2N2, Si2NP, and Si2P2. [Copyright &y& Elsevier]

Abstract: The mechanism of the cycloaddition reaction of forming a silapolycyclic compound between singlet silylidene and formaldehyde has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the cycloaddition reaction process of forming the silapolycyclic compound (P2) for this reaction consists of four steps: (I) the two reactants first form a semi-cyclic intermediate INT1a through a barrier-free exothermic reaction of 32.5kJmol−1; (II) this intermediate then isomerizes to an active four-membered ring intermediate INT1 via a transition state TS1a with an energy barrier of 30.8kJmol−1; (III) INT1 further reacts with formaldehyde to form an intermediate INT2, which is also a barrier-free exothermic reaction of 30.1kJmol−1; (IV) INT2 isomerizes to a silapolycyclic compound P2 via a transition state TS2 with a barrier of 50.6kJmol−1. Comparing this reaction path with other competitive reaction paths, we can see that this cycloaddition reaction has an excellent selectivity. [Copyright &y& Elsevier]

Abstract: The potential energy surface and the kinetics for the stepwise hydrogenation reaction of BN–barrelene have been studied theoretically. The geometries of the stationary points are optimized at B3LYP/cc-pVTZ level of theory. The intrinsic reaction coordinate (IRC) curve of reactions have been calculated by using the same level. The corrected barrier at the B3LYP/cc-pVTZ+ZEP level is 43.18, 40.17 and 41.12kcal/mol for the stepwise hydrogenation reactions of BN–barrelene, respectively. The rate constants are calculated with the conventional transition-state theory (TST) and RRKM theorey with the Eckart tunnel correction. The kinetics data indicates that BN–barrelene series compounds might be potential hydrogen-storage compounds. [Copyright &y& Elsevier]

Abstract: Although the rate constants of the C3H5+NO reaction were determined more than 20 years ago, no theoretical investigations have been reported up to now. In present paper, we performed a detailed mechanistic study on this reaction by constructing a singlet potential energy surface [C3H5NO] at the CCSD(T)/6-311G(d,p) //B3LYP/6-311G(d,p) level. The most favorable entrance channel is the direct radical–radical combination to form isomer H2CCHCH2NO m1 (−23.44kcal/mol). The calculated zero barrier is consistent with the determined high rate constant at room temperature. Except dissociation back to the reactants, the further conversion of m1 needs to overcome the transition states with energies being at least 23kcal/mol higher than the reactant. This is indicative of a distinct pressure dependence of the rate constants, which is also consistent with the experimental finding. The energetically very low-lying products P 1 CH2CHCN+H2O (−71.36kcal/mol), P 2 CH3CHO+HCN (−72.61kcal/mol) and P 3 CH3CHO+HNC (−57.55kcal/mol), however, cannot be reached kinetically. [Copyright &y& Elsevier]

Abstract: An extensive quantum chemical study of the potential energy surface (PES) for all possible isomerization and dissociation reactions of CH2CO with NCO is reported at the DFT (B3LYP/6-311++G(d,p)) and CCSD(T)/cc-pVDZ//B3LYP/6-311++G(d,p) levels of theory. For the CH2CO+NCO reaction, the formation of CO+CH2NCO via an addition–elimination mechanism is the dominant channel on the doublet surface. While the formation of CO+CH2OCN via bimolecular substitution reaction is in the secondary. Meanwhile, the isomerization and dissociation reactions of the products, CH2NCO and CH2OCN, also have been investigated using the same theoretical approach. It can be concluded that these reaction channels are not feasible kinetically at low or fairly high temperatures. On the basis of the ab initio data, the total rate constants for the CH2CO+NCO reaction in the T=296–560K range have been computed using conventional transition state theory with Wigner tunneling correction and fitted by a rate expression as k=2.14×10−12 (cm3 molecule−1 s−1) exp(654.29/T). The calculated total rate constants with Wigner tunneling correction for the CH2CO+NCO reaction are in good agreement with the available experimental values. [Copyright &y& Elsevier]

Abstract: Hydrogen and fluorine addition reactions with C28(T d ) have been investigated by the density function theory method at B3LYP/6-31G level. The interaction potential between C28(T d ) and atom X (X=H and F) shows that there are three possible stable isomers of C28(T d )X (X=H and F) and the average binding energy calculations suggest that C28(T d )H4 is the most stable hydrogen adduct among C28(T d )H n (n=1–28). Furthermore, by comparisons of the energy between C28(T d )H and C28(C s )H we found that the former are more stable than the later, and the structural and energy analysis further indicate that C28(C s )H is only with a small distortion of C28(T d )H symmetry. In addition, the transition states, as well as reaction pathways of X transfer reactions between different key points on C28(T d ) representative patch are given to explore the possible reaction mechanism. [Copyright &y& Elsevier]

Abstract: The structures, energetics, spectroscopies, and stabilities of the doublet PC2S radical are explored at density functional theory and ab initio levels. Seven minimum isomers are located connected by 20 interconversion transition states. At the CCSD(T)/6-311+G(2df)//QCISD/6-311G(d)+ZPVE level, the lowest-lying isomer is a linear form PCCS 1 whose structure mainly resonates between and with the former bearing somewhat more weight. The species 1 is predicted to possess great kinetic stability about 50kcal/mol. Additionally, two high-lying isomers, i.e. bent CCPS 2 (52.0) and bent CCPS 2′ (54.9), are also stabilized by the considerable barriers of 21.0 and 18.1kcal/mol, respectively. Interestingly, the isomers 2 and 2′ can be easily converted to each other, both of them could coexist. All the three isomers should be experimentally or astrophysically observable. The bonding natures of the isomers 1, 2, and 2′ are analyzed. Their molecular properties including adiabatic ionization potentials and adiabatic electronic affinities are determined at the higher levels G3//B3LYP and G3(MP2)//B3LYP. The calculated results are compared with those of the analogues NC2S and NC2O. Possible formation strategies of the isomers 1, 2, and 2′ in laboratory and in space are also discussed. The present PC2S work represents the first detailed potential energy survey of the PC n S (n>1) series and can provide useful information for future laboratory and interstellar identification of various PC2S isomers. [Copyright &y& Elsevier]

Abstract: Mechanisms of cycloaddition reaction between singlet vinylidene and acetone have been investigated with MP2/6-31G* method. Energies for the involved conformations are further improved using CCSD(T)//MP2/6-31G* and MP2/6-311G**//6-31G* for the geometries optimized with MP2/6-31G* method. On the basis of the potential energy surface profile, it can be predicted that the dominant reaction pathway for the reaction consists of three steps: (1) the two reactants firstly form an active four-membered ring intermediate, INT2, which is a barrier-free exothermic reaction, ΔE=−81.6kJ/mol (−95.0kJ/mol, MP2/6-311G**//6-31G*); (2) the intermediate INT2 further reacts with acetone to form a polycyclic intermediate, INT3, through a barrier-free exothermic reaction, ΔE=−31.0kJ/mol (−32.3kJ/mol, MP2/6-311G**//6-31G*); (3) INT3 isomerizes to a polycyclic product P3 via a transition state TS3 with an energy barrier of 25.1kJ/mol (21.2kJ/mol, MP2/6-311G**//6-31G*). [Copyright &y& Elsevier]

Abstract: The reaction of linear form carbon cluster C3 molecules in their 1Σ ground state with NO (X2Π) radicals is explored theoretically to investigate the formation of hitherto undetected NCCCO molecules in the interstellar medium via a neutral-neutral reaction. The doublet potential energy surface is worked out by the ab initio MO calculations at the CCSD(T)/cc-pVTZ//B3LYP/6-311G(d,p)+ZPE level of theory. It is shown that the main pathway of the C3(1Σ)+NO(X2Π) reaction involves the N-atom of NO attacking the side C-atom of the 1C3 molecule first to form the adduct CCCNO, followed by the N-shift to give I6 CCNCO, and then to the main products P1 (CCN+CO). Alternatively, I6 can be converted via the N-shift again to I9 (CN)CCO, and then it leads to the minor products P2 (CNC+CO) and P3 NCCCO. Since the three pathways have zero threshold energy and proceed via strongly bound energized complexes, they should possess the character of negative temperature dependence, and might be quite rapid even at very low temperature. The reaction represents facile neutral-neutral pathways to produce hitherto undetected CCN, CNC and NCCCO molecules in interstellar environments. [Copyright &y& Elsevier]

Abstract: The reaction for N(4S)+C2H5 has been studied by DFT method. The geometries of the reactants, the intermediates, the transition states and the products are optimized at the B3LYP/6-311G(d,p) level. The corresponding vibration frequencies are calculated at the same level. The single-point calculations for all the stationary points are carried out at the QCISD(T)/6-311+G(d,p) level using the B3LYP/6-311G(d,p) optimized geometries. The all energies were refined at the G3B3 level. The results of the theoretical study indicate that the major products are the C2H4+3NH and H2CN+CH3 in the reaction. The majority of the products C2H4+3NH are formed via a direct hydrogen abstraction pathway c1: (R)→TS1→(C). While the products H2CN+CH3 are produced via an addition/elimination pathway a: (R)→IM1→TS2→(A). In addition, the CH3CHN+H are found to be the possible products. Furthermore, the products CH3CHN and H2CN can undergo dissociation into the products HCN and CH3CN at higher temperatures. [Copyright &y& Elsevier]

Abstract: The doublet potential energy surface for the reactions 3NCN+NO, 3CNN+NO, 1NNO+CN and 2N3+CO is studied at the B3LYP/6-311G(d) and G2M(cc3) (single-point) levels of theory. For the reaction 3NCN+NO, the pathways 3NCN+NO⇌1 trans-ONNCN→2 cis-ONNCN→1NNO+CN and 3NCN+NO⇌2 cis-ONNCN→1NNO+CN are the major pathways. For the reaction 3CNN+NO, the pathway 3CNN+NO⇌3 trans-ONCNN→N2+2CNO is the major pathway. For the reaction 1NNO+CN, the pathways 1NNO+CN⇌2 cis-ONNCN→3NCN+NO and 1NNO+CN⇌2 cis-ONNCN→1 trans-ONNCN→3NCN+NO are the major pathways. For the reaction 2N3+CO, the pathways 2N3+CO⇌7 trans-OCNNN→N2+2NCO and 2N3+CO⇌7 trans-OCNNN→8 cis-OCNNN→N2+2NCO are the major pathways. In addition, the quartet potential energy surface for these reactions is also considered, but no favorable pathways can be found on it. [Copyright &y& Elsevier]