Anharmonic effect of the dissociation rate constant of the unimolecular reactions of CH2XCHFO (X = H,F)

This study examines six unimolecular reactions of CH₂XCHFO (X?=?H,?F). The geometries of the reactions are optimized with Gaussian 03. The calculated barrier heights show that bond C–C′ scission, CH₂XCHFO (X?=?H,?F)?→?CH₂X?+?CHFO (R1), dominates the decomposition of CH₂XCHFO. For X?=?H and X?=?F, the barrier heights of (R1) are 13.37 and 9.67?kcal?mol^?1, respectively. The YL (Yao and Lin) method is used to calculate the anharmonic and harmonic rate constants of the unimolecular reactions. The results clearly demonstrate the anharmonic effect of these reactions. In the microcanonical case, for (R1) (X?=?H), the total energy is from 42.78 to 144.84?kcal?mol^?1. The corresponding anharmonic rate constants are from 1.57?×?10¹² to 2.52?×?10^13?s^?1 and the harmonic rate constants are from 1.52?×?10¹² to 2.52?×?10^13?s^?1.     

Computational study on structures,thermochemical properties,and bond energies of disulfide oxygen (S–S–O)‐bridged CH3SSOH and CH3SS(=O)H and radicals

Cleavage of disulfide bonds is a common method used in linking peptides to proteins in biochemical reactions. The structures, internal rotor potentials, bond energies, and thermochemical properties (Δ_fH°, S°, and Cp(T)) of the S–S bridge molecules CH₃SSOH and CH₃SS(=O)H and the radicals CH₃SS?=O and C?H₂SSOH that correspond to H‐atom loss are determined by computational chemistry. Structure and thermochemical parameters (S° and Cp(T)) are determined using density functional Becke, three‐parameter, Lee–Yang–Parr (B3LYP)/6‐31++G (d, p), B3LYP/6‐311++G (3df, 2p). The enthalpies of formation for stable species are calculated using the total energies at B3LYP/6‐31++G (d, p), B3LYP/6‐311++G (3df, 2p), and the higher level composite CBS–QB3 levels with work reactions that are close to isodesmic in most cases. The enthalpies of formation for CH₃SSOH, CH₃SS(=O)H are ?38.3 and ?16.6 kcal mol^?1, respectively, where the difference is in enthalpy RSO–H versus RS(=O)–H bonding. The C–H bond energy of CH₃SSOH is 99.2 kcal mol^?1, and the O–H bond energy is weaker at 76.9 kcal mol^?1. Cleavage of the weak O–H bond in CH₃SSOH results in an electron rearrangement upon loss of the CH₃SSO–H hydrogen atom; the radical rearranges to form the more stable CH₃SS· = O radical structure. Cleavage of the C–H bond in CH₃SS(=O)H results in an unstable [CH₂SS(=O)H]* intermediate, which decomposes exothermically to lower energy CH₂ = S + HSO. The CH₃SS(=O)–H bond energy is quite weak at 54.8 kcal mol^?1 with the H–C bond estimated at between 91 and 98 kcal mol^?1. Disulfide bond energies for CH₃S–SOH and CH3S–S(=O)H are low: 67.1 and 39.2 kcal mol^?1. Copyright © 2011 John Wiley & Sons, Ltd.     

Computational studies on the thermal decomposition of the CH2FOCHFO radical

Theoretical studies have been carried out on the kinetics and thermochemistry of the thermal decomposition of the CH₂FOCHFO radical formed during the photo-oxidation of CH₂FOCH₂F (HFE-152E) using the dual-level method of obtaining the optimised structure at DFT(M06-2X)/6-311++G(d,p) followed by a single-point energy calculation at the G3 level of theory. The rate constant for different reaction channels involved during the decomposition processes of CH₂FOCHFO is evaluated at 298 K and 1 atm using canonical transition-state theory. The results point out that the C–H bond scission is the dominant path involving an energy barrier of 9.5 kcal mol^?1 determined at the G3 level of theory. A potential energy diagram is constructed and the results are compared with the data available from the literature for a structurally similar molecule.     

Thermochemistry,bond energies and internal rotor barriers of methyl sulfinic acid,methyl sulfinic acid ester and their radicals

Sulfur–Oxygen containing hydrocarbons are formed in oxidation of sulfides and thiols in the atmosphere, on aerosols and in combustion processes. Understanding their thermochemical properties is important to evaluate their formation and transformation paths. Structures, thermochemical properties, bond energies, and internal rotor potentials of methyl sulfinic acid CH₃S(?O)OH, its methyl ester CH₃S(?O)OCH₃ and radicals corresponding to loss of a hydrogen atom have been studied. Gas phase standard enthalpies of formation and bond energies were calculated using B3LYP/6‐311G (2d, p) individual and CBS‐QB3 composite methods employing work reactions to further improve accuracy of the ${\Delta} _{{\bf f}} H_{{\bf 298}}^{{\bf o}} $ . Molecular structures, vibration frequencies, and internal rotor potentials were calculated. Enthalpies of the parent molecules CH₃S(?O)OH and CH₃S(?O)OCH₃ are evaluated as ?77.4 and ?72.7 kcal mol^?1 at the CBS? QB3 level; Enthalpies of radicals C^?H₂? S(?O)? OH, CH₃? S^?(?O)₂, C^?H₂? S(?O)? OCH₃ and CH₃? S(?O)? OC^?H₂ (CBS‐QB3) are ?25.7, ?52.3, ?22.8, and ?26.8 kcal mol^?1, respectively. The CH₃C(?O)O—H bond dissociation energy is of 77.1 kcal mol^?1. Two of the intermediate radicals are unstable and rapidly dissociate. The CH₃S(?O)? O. radical obtained from the parent CH₃? S(?O)? OH dissociates into methyl radical (${\bf CH}_{{\bf 3}}^{{\bf .}} $ ) plus SO₂ with endothermicity (ΔH_rxn) of only 16.2 kcal mol^?1. The CH₃? S(?O)? OC^?H₂ radical dissociates into CH₃? S^?=O and CH₂=O with little or no barrier and an exothermicity of ?19.9 kcal mol^?1. DFT and the Complete Basis Set‐QB3 enthalpy values are in close agreement; this accord is attributed to use of isodesmic work reactions for the analysis and suggests this combination of B3LYP/work reaction approach is acceptable for larger molecules. Copyright © 2010 John Wiley & Sons, Ltd.     

Theoretical studies of ethylene addition to transition metal compounds with carbene and oxo groups LnM(CH2)(O)

Quantum chemical calculations using density functional theory at the B3LYP level in combination with relativistic effective core potentials for the metals and TZ2P valence basis sets have been carried out for elucidating the reaction pathways of ethylene addition to MeReO₂(CH₂) ( C1 ). The results are compared with our previous studies of ethylene addition to OsO₂(CH₂)₂ ( A1 ) and OsO₃(CH₂) ( B1 ). Significant differences have been found between the ethylene additions to the osmium compounds A1 and B1 and the rhenium compound C1 . Seven pathways for the reaction C1 +C₂H₄ were studied, but only the [2+2]_Re,C addition yielding rhenacyclobutane C5 is an exothermic process with a high activation barrier of 48.9 kcal mol^?1. The lowest activation energy (27.7 kcal mol^?1) is calculated for the [2+2]_Re,C addition, which leads to the isomeric form C5 ′. Two further concerted reactions [3+2]_O,C, [3+2]_O,O, and [2+2]_Re,O and the addition/hydrogen migration of ethylene to one oxo ligand are endothermic processes which have rather high activation barriers (>35 kcal mol^?1). Four isomerization processes of C1 have very large activation energies of >65 kcal mol^?1. The ethylene addition to the osmium compounds A1 and B1 are much more exothermic and have lower activation barriers than the C₂H₄ addition to C1 . Copyright © 2007 John Wiley & Sons, Ltd.     

The 1,2-hydrogen shift reaction for monohalogenophosphanes PH2X and HPX (X = F,Cl)

The aim of the present study was to perform a quantum chemical investigation in the 1,2-hydrogen shift reaction for the PH₂X and HPX molecules (X = F,Cl). Several phosphorus–halogen-bearing molecules were studied, including PH₂F, PH₂Cl, HPF, HPCl, HPFH, HPClH, PFH and PClH. The energies of stationary and saddle points on the ground electronic potential energy surface were investigated with post-Hartree–Fock methods [CCSD(T), MP2, QCISD] and different DFT functionals. The PH₂F 1,2-hydrogen shift energy barrier was 75 kcal mol^?1 at the CCSD(T) level and only a small increase in this value was observed for the HPF isomerisation. In contrast, the HPCl 1,2-hydrogen shift barrier is higher than the PH₂Cl one, which presented a barrier height of 69 kcal mol^?1 among CCSD(T) and composite methods. The rate constants of these unimolecular rearrangements varied from 10^?44 to 10^?38 s^?1, and these isomerisation channels exhibited large half-lives. In addition, the heat of formation of each monohalogenophosphane was also calculated. The Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) analysis were also employed to characterise the differences between the phosphorous–halogen bonds.     

Comparison of the Kinetics of the Exchange Mechanism of the Thallium Ion with 18C6 and with Pentaglyme in Acetonitrile Solutions

Abstract

In acetonitrile solutions, the exchange reaction is bimolecular in the Tl⁺ + 18C6 system, while in the Tl⁺ + pentaglyme system the associative-dissociative and the bimolecular mechanisms coexist at room temperature and the bimolecular exchange reaction dominates at 263° K. For the bimolecular mechanism in the case of Tl⁺ + 18C6 and the associative-dissociative mechanism in the case of Tl⁺ + pentaglyme, the activation energies of the exchange reactions change with temperature. At 298° K, in the Tl⁺ + 18C6 system the activation energy for the bimolecular exchange reaction is ≈ 2 kcal.mol^?1 and exchange rate constant (k₁) is (4.1 ± 0.1) × 10⁷ s^?1mol^?1; in the Tl⁺ + pentaglyme system, the activation energy for the associative-dissociative exchange reaction is ≈ 5 kcal mol^?1 and the decomplexation rate constant (k_?2) is (2.2 ± 0.4) X 10⁵ s^?1. The activation energy for the bimolecular exchange in the Tl⁺ + pentaglyme system was determined to be 3.00 ± 0.05 kcal.mol_?1 and the exchange rate constant (3.0 ± 0.1) X 10⁸ s^?1 mol^?1.     

The kinetics of D2 desorption from Ni(110) (2 × 1)C in the presence of reactive intermediates

A kinetic study of D₂ formation from HCOOD decomposition on Ni(110) (2 × 1)C was performed using the flash desorption technique. The surface structure and surface composition were monitored by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Flash curves were obtained using initial coverage and heating rate variations. D₂ formation exhibited a single second-order rate-determining step. Three different techniques were employed in obtaining the activation energy, two of which did not require the assumption of reaction order. Using an average value of 12.6 kcal/mole for the activation energy the pre-exponential factor was calculated to be 2.7 × 10^?4 cm² molecules^?1 sec^?1. Good agreement was achieved with the theoretically generated second-order flash curves only up to the peak temperature. The discrepancy on the high temperature side was explained using the model proposed by Clavenna and Schmidt utilizing a coverage dependent pre-exponential factor.     

Adsorption,coadsorption, and reactivity of sodium and nitric oxide on Ag(111)

The adsorption, desorption, and surface structural properties of Na and NO on Ag(111), together with their coadsorption and surface reactivity, have been studied by LEED, Auger spectroscopy, and thermal desorption. On the clean surface, non-dissociative adsorption of NO into the a-state occurs at 300 K with an initial sticking probability of ~0.1, saturation occurring at a coverage of $\text{~}\text{1}\text{20}$. Desorption occurs reversibly without decomposition and is characterised by a desorption energy of E_d ~ 103 kJ mol^?1. In the coverage regime 0 < θ_Na < 1, sodium adsorbs in registry with the Ag surface mesh and the desorption spectra show a single peak corresponding to E_d ~ 228 kJ mol^?1. For multilayer coverages (1 < θ _Na < 5) a new low temperature peak appears in the desorption spectra with E_d ~ 187 kJ mol^?1. This is identified with Na desorption from an essentially Na surface, and the desorption energy indicates that Na atoms beyond the first chemisorbed layer are significantly influenced by the presence of the Ag substrate. The LEED results show that Na multilayers grow as a (√7 × √7) R19.2° overlayer, and are interpreted in a way which is consistent with the above conclusion. Coadsorption of Na and NO leads to the appearance of a more strongly bound and reactive chemisorbed state of NO (β-NO) with E_d ~ 121 kJ mol^?1. β-NO appears to undego surface dissociation to yield adsorbed O and N atoms whose subsequent reactions lead to the formation of N₂, N₂O, and O₂ as gaseous products. The reactive behaviour of the system is complicated by the effects of Na and O diffusion into the bulk of the specimen, but certain invariant features permit us to postulate an overall reaction mechanism, and the results obtained here are compared with other relevant work.     

The adsorption of CO,H2, H2, CO2 and H2O on carburized and graphitized Ni(110)

A study of the adsorption/desorption behavior of CO, H₂O, CO₂ and H₂ on Ni(110)(4 × 5)-C and Ni(110)-graphite was made in order to assess the importance of desorption as a rate-limiting step for the decomposition of formic acid and to identify available reaction channels for the decomposition. The carbide surface adsorbed CO and H₂O in amounts comparable to the clean surface, whereas this surface, unlike clean Ni(110), did not appreciably adsorb H₂. The binding energy of CO on the carbide was coverage sensitive, decreasing from 21 to 12 $\text{kcal}\text{mol}$ as the CO coverage approached 1.1 × 10¹⁵ molecules cm^?2 at 200K. The initial sticking probability and maximum coverage of CO on the carbide surface were close to that observed for clean Ni(110). The amount of H₂, CO, CO₂ and H₂O adsorbed on the graphitized surface was insignificant relative to the clean surface. The kinetics of adsorption/desorption of the states observed are discussed.     

Quantum chemical studies of the solvation of the hydroxide ion

Abstract

To understand and model the solvation of the hydroxide ion, OH(H₂O)^? _n clusters, n = 1?5, are studied using ab initio quantum chemical techniques, largely at the MP2 level of theory using a double zeta plus polarization functions basis extended by diffuse functions. Energies and vibrational frequencies, together with thermodynamic quantities such as enthalpies, entropies and Gibbs free energies, are computed. This permits comparison with experimental estimates of the successive thermodynamic changes associated with the reaction OH(H₂O)^? _n + H₂O → OH(H₂O)^? _n+1. The theoretical values are in good agreement with experiment. The free energy of hydration of OH^? is modelled by a composite discrete-continuum method where the effects of the first hydration shell (n = 3) are obtained from the gas phase cluster calculation, while the long-range effects are modelled using self consistent reaction field theory, namely by calculating the solvation energy of OH(H₂O)^? _n in a dielectric continuum. The best estimate of the solvation (free) energy at 298 K is ?84·5 kcal mol^?1, compared to the experimental value of ?102·8 kcal mol^?1.     

Investigation of the kinetics of OH∗ and CH∗ chemiluminescence in hydrocarbon oxidation behind reflected shock waves

The temporal variation of chemiluminescence emission from OH^?(A² Σ ⁺) and CH^?(A² Δ) in reacting Ar-diluted H₂/O₂/CH₄, C₂H₂/O₂ and C₂H₂/N₂O mixtures was studied in a shock tube for a wide temperature range at atmospheric pressures and various equivalence ratios. Time-resolved emission measurements were used to evaluate the relative importance of different reaction pathways. The main formation channel for OH^? in hydrocarbon combustion was studied with CH₄ as benchmark fuel. Three reaction pathways leading to CH^? were studied with C₂H₂ as fuel. Based on well-validated ground-state chemistry models from literature, sub-mechanisms for OH^? and CH^? were developed. For the main OH^?-forming reaction CH+O₂=OH^?+CO, a rate coefficient of k ₂=(8.0±2.6)×10¹⁰ cm³?mol^?1?s^?1 was determined. For CH^? formation, best agreement was achieved when incorporating reactions C₂+OH=CH^?+CO (k ₅=2.0×10¹⁴ cm³?mol^?1?s^?1) and C₂H+O=CH^?+CO (k ₆=3.6×10¹²exp(?10.9 kJ?mol^?1/RT) cm³?mol^?1?s^?1) and neglecting the C₂H+O₂=CH^?+CO₂ reaction.     

A high level computational study of the CH4/CF4 dimer: how does it compare with the CH4/CH4 and CF4/CF4 dimers?

The interaction within the methane–methane (CH₄/CH₄), perfluoromethane–perfluoromethane (CF₄/CF₄) methane–perfluoromethane dimers (CH₄/CF₄) was calculated using the Hartree–Fock (HF) method, multiple orders of Møller–Plesset perturbation theory [MP2, MP3, MP4(DQ), MP4(SDQ), MP4(SDTQ)], and coupled cluster theory [CCSD, CCSD(T)], as well as the PW91, B97D, and M06-2X density functional theory (DFT) functionals. The basis sets of Dunning and coworkers (aug-cc-pVxZ, x?=?D, T, Q), Krishnan and coworkers [6-311++G(d,p), 6-311++G(2d,2p)], and Tsuzuki and coworkers [aug(df, pd)-6-311G(d,p)] were used. Basis set superposition error (BSSE) was corrected via the counterpoise method in all cases. Interaction energies obtained with the MP2 method do not fit with the experimental finding that the methane–perfluoromethane system phase separates at 94.5?K. It was not until the CCSD(T) method was considered that the interaction energy of the methane–perfluoromethane dimer (?0.69?kcal?mol^?1) was found to be intermediate between the methane (?0.51?kcal?mol^?1) and perfluoromethane (?0.78?kcal?mol^?1) dimers. This suggests that a perfluoromethane molecule interacts preferentially with another perfluoromethane (by about 0.09?kcal?mol^?1) than with a methane molecule. At temperatures much lower than the CH₄/CF₄ critical solution temperature of 94.5?K, this energy difference becomes significant and leads perfluoromethane molecules to associate with themselves, forming a phase separation. The DFT functionals yielded erratic results for the three dimers. Further development of DFT is needed in order to model dispersion interactions in hydrocarbon/perfluorocarbon systems.     

A DFT study on the formation of CH3O on Cu2O(1 1 1) surface by CH3OH decomposition in the absence or presence of oxygen

The formation mechanism of CH₃O by the adsorption and decomposition of CH₃OH on clean and oxygen-precovered Cu₂O(1 1 1) surface has been investigated with density functional theory method together with the periodic slab models. Two possible formation pathways of CH₃O by CH₃OH decomposition on oxygen-precovered (O_pre) Cu₂O(1 1 1) surface were proposed and discussed. One is the O-H bond-cleavage of CH₃OH with H migration to O_pre to form CH₃O; the other is the C-O bond-scission of CH₃OH with CH₃ migration to O_pre leading to CH₃O_pre. The calculated results show that the O-H bond-breaking path has the lowest activation barrier 26.8 kJ mol⁻¹, the presence of oxygen-precovered on Cu₂O(1 1 1) surface exhibits a high surface reactivity toward the formation of CH₃O by the O-H bond-cleavage of CH₃OH, and reduce the activation barrier of O-H bond-cleavage. The C-O bond-breaking path was inhibited by dynamics, suggesting that the O atom of CH₃O is not from the oxygen-precovered, but comes from the O of CH₃OH. Meanwhile, the calculated results give a clear illustration about the formation mechanism of CH₃O in the presence of oxygen and the role of oxygen at the microscopic level.     

Accurate ab initio anharmonic force field and heat of formation for silane

From large basis set coupled cluster calculations and a minor empirical adjustment, an anharmonic force field for silane has been derived that is consistently of spectroscopic quality (±1 cm^?1 on vibrational fundamentals) for all isotopomers of silane studied. Inner-shell polarization functions have an appreciable effect on computed properties and even on anharmonic corrections. From large basis set coupled cluster calculations and extrapolations to the infinite-basis set limit, we obtain TAE₀ = 303.80 ± 0.18 kcal mol^?1, which includes an anharmonic zero-point energy (19.59 kcal mol^?1), inner-shell correlation (—0.36 kcal mol^?1), scalar relativistic corrections (— 0.70 kcal mol^?1) and atomic spin-orbit corrections (—0.43 kcal mol^?1). In combination with the recently revised ΔH ^o _{f, o}[Si(g)], we obtain ΔH ^o _f.o[SiH₄(g)] = 9.9 ± 0.4 kcal mol^?1 in between the two established experimental values.     

A static SIMS/TPD study of the kinetics of methoxy formation and decomposition on O/Pt(111)

The kinetics and mechanism of the decomposition of methanol (CH₃OD) on oxygen-covered Pt(111) were studied using static secondary ion mass spectrometry (SIMS) and temperature programmed desorption (TPD). The initial sticking coefficient and the saturation first layer coverage of CH₃OD are unity and 0.36 ML, respectively. The maximum amounts decomposed in TPD on O/Pt(111) and clean Pt(111) are 0.19 and 0.047 ML, respectively. At low methanol coverages (< 0.05 ML) on O/Pt(111) the only reaction products were CO₂, H₂O and D₂O, whereas at saturation CO, H₂O, D₂O and H₂ were observed. The decomposed amount did not saturate at or before the onset of molecular methanol desorption, but increeased monotonically until saturation of the first layer. No oxygen exchange was observed between CH₃OD and preadsorbed ¹⁸O. A decomposition mechanism involving methoxy and hydroxyl type species is proposed. Methanol coverages as low as 0.002 ML could be detected with SIMS. The CH₃⁺ ion was the most intense ion in the positive SIMS spectrum of both methanol and methoxy. Larger ion clusters such as (CH₃OD)_n⁺ (n = 2, 3) developed successively at specific multilayer coverages. At low coverages on O/Pt(111), methoxy formation occurs above 125 K and its decomposition becomes detectable above 150 K during temperature programming. In the isothermal mode, the SIMS CH₃⁺ ion was used to follow the kinetics. Over the temperature range 120–145 K, the second order Arrhenius rate parameters for methoxy formation are E = 5.5±0.7 kcal/mol and A = 1.5×10^−7±0.6 cm²/s·molecule for an initial methanol coverage of 0.05 ML. Methoxy decomposition was studied in the temperature range 150–165 K and at an initial coverage of 0.015 ML. The first order kinetic parameters, E = 11.4±0.5 kcal/mol and A = 5.3×10^13±1 s⁻¹ were derived. Advantages and limitations of using SIMS as a tool for kinetic studies are discussed.     

Theoretical investigation of an unusual substituent effect on the dienophilicity of >CP? functionality present in 2‐phosphaindolizines

Effect of the number and positions of the methoxycarbonyl substituents in 2‐phosphaindolizine on the feasibility of its Diels–Alder (DA) reaction with 1,3‐butadiene has been investigated theoretically at the density functional theory (DFT) level. Among the series of four differently substituted 2‐phosphaindolizines, 3‐methoxycarbonyl‐2‐phosphaindolizine does not undergo the DA reaction due to the highest activation barrier (29.49 kcal mol^?1) and endothermicity, whereas the activation barrier of the corresponding reaction of 1,3‐bis(methoxycarbonyl)‐2‐phosphaindolizine is lowest (22.43 kcal mol^?1) with exothermicity making it possible to occur. This reactivity trend is corroborated by FMO energy gaps as well as by global electrophilicity powers of the reactants. Copyright © 2008 John Wiley & Sons, Ltd.     

An insight into the reaction kinetics of CH3 + O2(a1Δg) and its enhancement effect on methane ignition

The reaction between CH₃ and O₂(a¹?_g) is crucial to understand the effects of electronically excited oxygen in plasma-assisted combustion of methane and other hydrocarbons. In the present work, multireference quantum chemical methods were used to investigate the potential energy surface of CH₃ + O₂(a¹?_g). The RRKM/master equation simulation was employed to compute the rate coefficients of various pathways to this reaction over the temperature range of 300–2000 K and a pressure range of 0.1–100 atm. Special attention has been paid to the nonadiabatic transition between the excited state and ground state, which directly leads to a quenching channel from CH₃ + O₂(a¹?_g) to CH₃ + O₂(X³∑_g^?). This quenching reaction has been overlooked by previous theoretical and kinetic modeling studies. We also conducted kinetic modeling to examine the effect of this reaction on the ignition enhancement of methane oxidation. Although the channel of CH₃ + O₂(a¹?_g) quenching to CH₃ + O₂(X³∑_g^?) has nonnegligible rate constants comparing with other reaction channels, modeling result with the inclusion of 5% O₂(a¹?_g) in molecular oxygen shows that the titled reactions shorten the ignition delay time of methane by more than twenty times at 900 K, 1 atm. The ignition enhancement is mainly from the chain branching channels to CH₂O + OH and CH₃O + O which has been greatly promoted by excess energy from O₂(a¹?_g). The present study uncovers the kinetic mechanism of this nonadiabatic reaction and provides reasonable rate coefficients for further kinetic modeling of plasma-assisted combustion of methane and other hydrocarbons.     

Characterization of the adsorption and decomposition of methanol on Ni(110)

The chemisorption, condensation, desorption, and decomposition of methanol, both CH₃OH and CH₃OD, on a clean Ni(110) surface have been characterized using high resolution electron energy loss spectroscopy, temperature programmed reaction spectroscopy, and low energy electron diffraction. The vibrational spectrum of the saturated chemisorbed layer, 7.4 × 10¹⁴ molecules cm^?2, is almost identical to the infrared spectrum of liquid or solid methanol. Condensation of multilayers of methanol is facile at 80 K. The only quasi-stable intermediate isolated during the decomposition is a methoxy species, CH₃O, which decomposes thermally to CO and H. The evolution of both CO and H₂ occurs in desorption limited processes.