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1.
Michael A. Parkes Jessica F. Lockyear Stephen D. Price 《International journal of mass spectrometry》2009,280(1-3):85
The reaction between Ar2+ and C2H2 has been studied, at centre-of-mass collision energies ranging from 3 to 7 eV, using a position-sensitive coincidence technique to detect the monocation pairs, which are formed. Sixteen different reaction channels generating pairs of monocations have been observed, these channels arise from double-electron-transfer, single-electron-transfer and chemical reactions forming ArC+. Examination of the scattering diagrams and energetic information extracted from the coincidence data indicate that double-electron-transfer is a direct process, which does not involve a collision complex, and the derived energetics point towards a concerted, not stepwise, mechanism for the two-electron-transfer. As is commonly observed, single-electron-transfer from C2H2 to Ar2+ takes place via a direct mechanism, again not involving complexation. Most of the C2H2+ products that are formed in the single-electron-transfer reactions possess significant (12–15 eV) internal energy and fragment rapidly within the electric field of the partner Ar+ ion. The chemical reactions appear to proceed via a direct mechanism involving the initial formation of ArCH+, which subsequently fragments to form ArC+. 相似文献
2.
C2(a 3πu) disappearance rate constants of 1.44, 0.96, 0.0296, 0.0130 and < 10?6(x10?10cm3s?1) are reported for reactions with C2H4, C2H2, O2, C2H6, and CH4, respectively at 298 K. C2(a 3πu) fragments are generated by multiphoton ArF excimer laser photodissociation at C2H2, and monitored by dye laser induced fluorescence. Arguments are presented which favor chemical reactions over the C2(a 3πu) → (X 1σ+g) quenching channel. C2 + C2H2 represents the one possible exception to the reactive channel. 相似文献
3.
Experimental and Theoretical Study of Hydrogen Atom Abstraction from C2H6 and C4H10 by Zirconium Oxide Clusters Anions
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The reactions of anionic zirconium oxide clusters ZrxOy- with C2H6 and C4H10 are investi-gated by a time of flight mass spectrometer coupled with a laser vaporization cluster source.Hydrogen containing products Zr2O5H- and Zr3O7H- are observed after the reaction. Den-sity functional theory calculations indicate that the hydrogen abstraction is favorable in the reaction of Zr2O5- with C2H6, which supports that the observed Zr2O5H- and Zr3O7H- are due to hydrogen atom abstraction from the alkane molecules. This work shows a newpossible pathway in the reaction of zirconium oxide cluster anions with alkane molecules. 相似文献
4.
L. Yu. Ustynyuk E. A. Fushman S. S. Lalayan 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(8):1342-1349
Density functional theory was used to study gas-phase reactions between the Cp2*ZrMe+ cations, where Cp* = C5H5 (1), Me5Cp = C5Me5 (2), and Flu = C13H9 (3), and the ethylene molecule, Cp2*ZrMe+ + C2H4 → Cp2*ZrPr+ → Cp2*ZrAllyl+ + H2. The reactivity of the Cp2*ZrMe+ cations with respect to the ethylene molecule decreased in the series 1 > 3 ≈ 2. Substitution in the Cp ring decreased the reactivity of the Cp2*ZrMe+ cations toward ethylene, in agreement with the experimental data on the comparative reactivities of complexes 1 and 3. The two main energy barriers along the reaction path (the formation of the C-C bond leading to the primary product Cp2*ZrPr+ and hydride shift leading to the secondary product Cp2*Zr(H2)Allyl+) vary in opposite directions in the series of the compounds studied. For Flu (3), these barriers are close to each other, and for the other compounds, the formation of the C-C bond requires the overcoming
of a higher energy barrier. A comparison of the results obtained with the data on the activity of zirconocene catalysts in
real catalytic systems for the polymerization of ethylene led us to conclude that the properties of the catalytic center changed
drastically in the passage from the model reaction in the gas phase to real catalytic systems. 相似文献
5.
Experimental differential cross sections for 40 keV electrons scattered by C2H2, C2H4 and C2H6 molecules were measured using the gas electron diffraction method in the range of the scattering variable s from s = 1 A?1 to s = 30 A?1. The differential cross sections for neon were also measured and compared with calculated differential cross sections to calibrate the diffractograph. Experimental differential cross sections show significant deviations with respect to theoretical differential cross sections calculated from the Debye-Ehrenfest model, mainly in the range of small scattering angles. The observed differences are connected to chemical binding effects. From the experimental data, an estimation of the binding energy was carried out. The deduced values: ?0.58 ± 0.20 au for C2H2, ?0.94 ± 0.30 au for C2H4 and ?1.23 ± 0.40 au for C2H6 are in agreement with those obtained by thermochemical methods. 相似文献
6.
MINDO/3 calculations for singlet and triplet doubly charged benzene [C6H6]2+ are in satisfactory agreement with the experimentally determined values of the vertical double ionization energy of benzene; calculations for straight chain isomeric structures are consistent with the observed kinetic energy release on fragmentation to [C5H3]+ and [CH3]+. Symmetrical doubly charged benzene ions relax to a less symmetrical cyclic structure having sufficient internal energy to fragment by ring opening and hydrogen transfer towards the ends of the carbon chain. Fragmentation of [CH3C4CH3]2+ to [CH3C4]+ and [CH3]+ is a relatively high energy process (A), whereas both (B): [CH3CHC3CH2]2+ to [CHC3CH2]+ and [CH3]+ and (C): [CH3CHCCHCCH]2+ to [CHCCHCCH]+ and [CH3]+ may be exothermic processes from doubly charged benzene. Furthermore, the calculated energy for the reverse of process (A) is less than the experimentally observed kinetic energy released, whereas larger energies for the reverse of processes B and C are predicted. Heats of formation of homologous series [HCn]+, [CH3Cn]+, [CH2Cn?2CH]+, [CH3Cn?2CH2]+ and [CH2?CHCn?3CH2]+ with 1 < n < 6 are calculated to aid prediction of the most stable products of fragmentation of doubly charged cations. The homologous series [CH2Cn?2CH]+ is relatively stable and may account for ready fragmentation of doubly charged ions to [CnH3]+; alternatively the symmetrical [C5H3]+ ion [CHCCHCCH]+ may be formed. Dicoordinate carbon chains appear to be important stabilizing features for both cations and dications. 相似文献
7.
High pressure vapour-liquid equilibrium data for the C2H6 + N2, C2H4 + N2, C3H8 + N2, and C3H6 + N2 systems are presented. The data are obtained isothermally in the range from 200 K to 290 K. For each point of data, temperature, pressure and liquid and vapour phase mole fractions are measured.Values for the vapour phase mole fractions are calculated from the obtained pressure, temperature and liquid phase mole fractions. The calculated values are compared with the experimental results, and it is found that the average mean deviation between calculated and experimental mole fractions is less than 0.009 for the systems considered in this work. 相似文献
8.
V.A. Bhirud P.W. Kletnieks J.F. Haw M.M. Olmstead 《Journal of organometallic chemistry》2007,692(10):2107-2113
We report a new synthesis and characterization of Ir(C2H4)2(C5H7O2) [(acetylacetonato)-bis(η2-ethene)iridium(I)], prepared from (NH4)3IrCl6 · H2O in a yield of about 45%. The compound has been characterized by X-ray diffraction crystallography, infrared, Raman, and NMR spectroscopies and calculations at the level of density functional theory. Ir(C2H4)2(C5H7O2) is isostructural with Rh(C2H4)2(C5H7O2), but there is a substantial difference in the ethylene binding energies, with Ir-ethylene having a stronger interaction than Rh-ethylene; two ethylenes are bound to Ir with a binding energy of 94 kcal/mol and to Rh with a binding energy of 70 kcal/mol. 相似文献
9.
B. Levy 《Chemical physics letters》1973,18(1):59-62
The results of several MC SCF calculations on CH4, C2H4 and C2H6 with minimun bases of Slater type AO's are reported. The computing method is a quadratically convergent process. Better final energies are obtained if localized MO's are used. 相似文献
10.
Ab initio SCF and CEPA PNO calculations have been performed together with MINDO/3 calculations on the system C2H+7. In agreement with experimental assignment, but in contradiction to MINDO/3 results, the ab initio methods show the CC protonated structure to be more stable than the CH protonated structure. The energy difference is 8.5 kcal/mol at the SCF level and 6.3 kcal/mol with inclusion of electron correlation. Additionally, ΔH0300 for the reaction C2H+s + H2 = C2H+7 and the proton affinity of ethane are computed. 相似文献
11.
A. Drelinkiewicz P. Byszewski A. Bielanski 《Reaction Kinetics and Catalysis Letters》1996,59(1):19-27
Catalytic hydrogenation of C60 with H2 or by hydrogen transfer reactions using Pd/SiO2, Rh/Al2O3 and Ru/Al2O3 has been studied. The final products containing partially hydrogenated C60 fullerence C60H42–C60H46 were characterized by FTIR, UV and NMR methods. 相似文献
12.
N.M.M. Nibbering 《Tetrahedron》1973,29(2):385-390
The C6H6O+?ion from phenetole is generated by hydrogen transfer predominantly from the terminal-position, but also to some extent from the position next to oxygen. Deuterium labelling and ion-molecule reactions show that both transfers occur to the oxygen atom and not to the aromatic ring. The C6H6O+?ion is thus formed exclusively in the phenolic structure. 相似文献
13.
C.Q. Jiao J.A. Boatz C.A. DeJoseph Jr. A. Garscadden 《International journal of mass spectrometry》2009,288(1-3):22-35
C4H4+ reacts with pyridine (C5H5N) via the channels of proton transfer, charge transfer and condensation with H-elimination. The condensation reaction is of general interest in terms of basic chemistry and is the focus of the present study. By means of theoretical calculations and Fourier transform mass spectrometer experiments using deuterated pyridine and substituted pyridines, the structure of the product ion and the reaction pathways are investigated. From the experimental results we find that the H atom that is eliminated can originate from either pyridine or C4H4+. The experiments show that elimination of an H atom from C4H4+ is preferred and that there is an observable kinetic isotope effect. By replacing H atoms with methyl groups in ortho positions of pyridine, the experimental results also suggest possible steric blocking to the condensation. Based on the experimental observations and results of theoretical calculations of several possible structures of intermediates, transition states, and final product ions, a possible reaction scheme for the condensation-H-elimination is discussed. 相似文献
14.
Glyn R. John Leon A. P. Kane-Maguire Dwight A. Sweigart 《Journal of organometallic chemistry》1976,120(3)
Phosphonium adduct formation via attack of tri-n-butylphosphine on the cations [(C7H7)M(CO)3]+ (M = Cr, Mo, W) obeys the rate law, Rate = k [complex] [PBu3]. The very similar rate constants for the Cr, Mo and W complexes confirm the similar electrophilicities of the tropylium rings in these cations, and also support the view that there is direct addition to the rings. The related complexes [(C6H7)Fe(CO)3]BF4 and [(C6H6)Mn(CO)3]BF4 also form adducts with PBu3, and the quantitative reactivity order [(C6H7)Fe(CO)3]+ > [(C7H7)Cr(CO)3]+ » [(C6H6)Mn(CO)3]+ (160:60:1) has been established. 相似文献
15.
Three photocatalytic oxidation (PCO) systems: C7H16-O2, SO2-O2 and C7H16-SO2-O2 were carried out with the aid of UV-illuminated TiO2 nanoparticles at room temperature in a batch reactor. In C7H16-O2-TiO2 system, no catalyst deactivation was observed, while for SO2-O2-TiO2 and C7H16-SO2-O2-TiO2 systems, the photocatalytic activity of used TiO2 powder showed decreasing and eventually no activity after used consecutively. The reaction products such as sulfur trioxide or sulfuric acid adsorbed onto the surface of TiO2 catalyst were poisoning species. Photocatalytic activity of the deactivated TiO2 powder could be regenerated by sonicating treatment with water and methanol for the two systems, respectively. 相似文献
16.
M. Guilhaus R. G. Kingston A. G. Brenton J. H. Beynon 《Journal of mass spectrometry : JMS》1985,20(9):565-571
Mass-analysed ion kinetic energy spectra for collisional activation (CA) of [C6H6]+˙ formed via electron capture by [C6H6]2+ ions in collision with neutral benzene molecules have been compared for the C6H6 isomers benzene, 1,5-hexadiyne and 2,4-hexadiyne. Comparisons of fragment abundance and total CA fragment yields were also made for [C6H6]+˙ ions generated by electron ionization (EI). CA conditions of ion velocity and collision gas pressure were identical in these comparisons. In general the fragment abundance patterns for the ions formed by charge exchange were very similar to those for singly charged benzene ions generated by EI. However, significant variations in CA fragment yield (the ratio of the total CA fragment ion abundance to the abundance of the incident unfragmented ions) were observed. It is not clear from the results whether these variations reflect structurally different ions or ions of different internal energies. The CA spectra of [C6H6]+˙ ions derived from charge exchange reactions between the benzene dication and the target gases He, Ne, Ar, Kr and Xe have also been recorded and, once again, very similar fragment abundance patterns were observed along with large variations in total CA fragment yields. Charge exchange efficiency measurements are reported for reactions between the benzene dication and the targets He, Ne, Ar, Kr, Xe and C6H6 (benzene) and also for the doubly charged ions derived from the linear C6H6 isomers. In the latter case Xe and benzene targets were used. The energetics and efficiency measurements for the former reactions suggest that for targets such as He and Ne the processes probably involve excited states of the doubly charged ions. The efficiencies measured for the latter reactions were distinctly different for the three C6H6 isomers and may indicate a strong dependence of charge exchange cross-section on doubly charged ion structure. 相似文献
17.
B. E. Jones L. E. Abbey H. L. Chatham A. W. Hanner L. A. Teleshefsky E. M. Burgess T. F. Moran 《Journal of mass spectrometry : JMS》1982,17(1):10-18
Doubly charged ion mass spectra have been obtained for 15 n-alkane hydrocarbons. Spectra were measured using a Nier-Johnson geometry Hitachi RMU-7L mass spectrometer operated at 1.6kV accelerating voltage. Fragment ions, which resulted from C? C bond rupture and extensive H loss, dominated the spectra. Molecular ions have not been observed. The most intense ions in the doubly charged ion mass spectra of n-alkanes were [C2H4]2+, [C3H2]2+, [C4H3]2+, [C5H2]2+, [C6H6]2+, [C6H8]2+, [C7H6]2+, [C7H8]2+, [C8H6]2+ and [C8H8]2+. Appearance energies for forming the prominent doubly charged fragment ions have been measured and range from 27.5 eV to energies greater than 60eV. A geometry optimized SCF approach has been used to compute the energies and structures of prominent ions in the doubly charged mass spectra. 相似文献
18.
K.M. Harmon 《Journal of Molecular Structure》2002,612(1):65-68
An ab initio molecular orbital study shows that the face hydrogen of the zwitterionic hemiousene [7.111]-nido-(12)-7,8-dicarbahemiousene (C7H6+-B9C2H11−) is in a fluxional double minimum. It is primarily associated with B10 and forms unsymmetrical three-center bridges between B10-B9 or B10-B11. The transition barrier is about 2.5 kcal mol−1. This structure is similar to that of the unsubstituted C2B9H12− ion and demonstrates that the cationic tropyliumyl substituent has little effect on the face. The hypothetical completely symmetrical ion B11H123− does not have a centered face hydrogen. The hydrogen is involved in a short, symmetrical bridge between face borons, and would be presumably fully fluxional in solution. 相似文献
19.
A time-of-flight mass spectrometer has been modified to study directly the time dependence of metastable decay processes by introducing a variable time delay between the ionization and extraction pulses and by providing a set of retarding plates and grids in the flight tube to select a single parent ion species for study and to resolve the peak into parent ion, daughter ion and daughter neutral components. The experimentally determined time dependence of the unimolecular decay process C3H8+ → C3H7+ + H is compared with previously published predictions of the quasiequilibrium theory of mass spectra. 相似文献
20.
A. W. Hanner L. E. Abbey D. E. Bostwick E. M. Burgess T. F. Moran 《Journal of mass spectrometry : JMS》1982,17(1):19-28
Doubly charged ion mass spectra have been obtained for 42 chlorinated and brominated n-alkane (methyl through octyl) hydrocarbons. A double focusing Hitachi RMU-7L mass spectrometer, operated at 1.6kV accelerating voltage, has been used to measure the spectra. Molecular doubly charged ions have not been observed. Intense fragment ions have been produced from extensive H and halogen loss as well as C? C bond rupture of the parent molecule. The most abundant ions in the doubly charged ion spectra observed in this investigation resulted from reactions of [Cl]2+˙, [Br]2+˙, [CCL2]2+, [C2H2Cl]2+˙, [C3H2]2+, [C3HCl]2+, [C3HBr]2+, [C4H3]2+˙, [C4H4]2+, [C4H6Br]2+˙, [C4H8Br]2+˙, [C5H2]2+, [C6H6]2+, [C6H8]2+ and [C7H8]2+. The prominent doubly charged fragment ions formed by electron impact of the smaller halogenated alkanes generally contained halogen, whereas ions of the type [CnHx]2+ were dominant in the spectra of higher molecular weight mono- and dihalogenated alkanes. Appearance energies of several ions have been measured. A geometry optimized quantum mechanical SCF treatment has been used to compute energies, charge densities and structures of doubly charged halogenated alkane ions. 相似文献