14531-53-4Relevant articles and documents
Reactions of He+, Ne+, and Ar+ with CH4, C2H6, SiH4, and Si2H6
Chatham, H.,Hils, D.,Robertson, R.,Gallagher, A. C.
, p. 1301 - 1311 (1983)
The rate coefficients and product-ion distributions for the reactions of He+ and Ar+ with silane and disilane have been measured in a drift tube, typically for collision energies of 0.01-1 eV.The total charge-exchange rate coefficients are found to be roughly independent of E/N, or collision energy, and are about equal to the Langevin values for the reactions of He+ with SiH4 and C2H6 and Ar+ with CH4 and C2H6.The He+ rate coefficients on CH4 and Si2H6, and the Ne+ rate coefficients on SiH4 and Si2H6 are 50percent to 80percent of the Langevin values, while the Ar+ rate coefficients on SiH4 and Si2H6 are much smaller.Product ions tend to be hydrogen poor with very infrequent breaking of the C-C or Si-Si bonds.Furthermore, hydrogen stripping is more severe for the silanes than the alkanes.These product-ion distributions bear no resemblance to the product-ion distributions of either photoionization or electron collisional ionization.
A crossed-beam scattering study of CH4+ and CH3+ formation in charge transfer collisions of Kr+ with CH4 at about 1 eV
Herman, Zdenek,Friedrich, Bretislav
, p. 7017 - 7023 (1995)
The dynamics of CH4+ and CH3+ ion formation in collisions of Kr+(2P3/2'1/2) with thermal CH4 has been investigated in a crossed beam experiment at a hyperthermal collision energy of 1.18 eV.The scattering data show that the CH4+ product is formed in a near-resonant exoergic process in which the most probable energy transferred to the target is practically equal to the recombination energy of the Kr+ projectile (resonant energy transfer); in addition a wide band of internal states of CH4+ up to +/-0.6 eV is populated in inelastic and superelastic collisions.In contrast, the CH3+ product is formed in dissociative charge transfer, with about one-half of the yield due to nonresonant, endoergic collisions of Kr+ (2P3/2).The other half of the CH3+ product is found to originate in near-resonant exoergic collisions of Kr+ (2P1/2).An estimate is given of the distribution of the total energy deposited in methane by the above processes.
Dissociation dynamics of CH4+ core ion in the 2A1 state
Furuya, Kenji,Kimura, Katsumi,Sakai, Yasuhiro,Takayanagi, Toshinobu,Yonekura, Nobuaki
, p. 2720 - 2728 (1994)
Threshold-photoelectron photoion coincidence (TPEPICO) spectra of CH4 have been observed with synchrotron radiation at the excitation to the 2A1 (υ1=0-3) ionic states as well as to the 4pt2 Rydberg (υ1 = 0-4) states.In all the TPEPICO spectra observed, the CH3+ band shape was almost rectangular, which suggests that the translational and internal energy distributions of CH3+ are very narrow.The total kinetic energy releases (KERs) have been estimated from the CH3+ band shape.As a result, it was found that the CH3+ species were in an electronically excited state.There was a narrow distribution of the total KERs and similarity in the TPEPICO CH3+ band shapes between the spectra at the 2A1 ionic state and the 4pt2 Rydberg state excitations, which led to the conclusion that the Rydberg electron is just a spectator and the dissociation of the core ion plays an important role in dissociation through the 4pt2 Rydberg state.Similar results have also been obtained for CH2+ and CH+ productions.However, on the other hand, an H+ fragment has been observed only at the 2A1 state excitation.It showed a band with a long tail in the slower flight time region.The total average KERs and the decay rates have been estimated from band shape simulation.From these results, it has been found that a dissociation limit of the H+ ion exists just below the 2A1 ionic state.The dissociation mechanisms through the 4pt2 Rydberg state have been discussed in detail in comparison with those of the 2A1 ionic state.
Kinetics of the reaction of O2+ with CH4 from 500 to 1400 K: A case for state specific chemistry
Dotan,Viggiano
, p. 6112 - 6118 (2007/10/03)
The temperature dependent rate constants and branching ratios for the reaction of O2+ with CH4 and O2 with CD4 from 500 to 1400 K were determined. By comparing to previous studies, the influence on vibrational excitation in the CH4 reactant was derived.
Dissociative photoionization of CH3SSCH3 in the region of ～8-25 eV
Chiang, Su-Yu
, p. 9056 - 9063 (2007/10/03)
The dissociative photoionization of CH3SSCH3 has been investigated in the photon energy range of ～8-25 eV with a molecular beam/photoionization mass spectrometry/threshold photoelectron spectrometry system using synchrotron radiation as an ionization source. For dissociation above photon energy of 11.5 eV, six fragment ions of CH3+, C2H3+, SH3+, HCS+, S2+, and CH2S2+ were reported for the first time. The photoionization efficiency spectra for the parent ion and for 12 observed fragment ions, CH3+, C2H3+, SH3+, HCS+, CH2S+, CH2SH+, CH3SH+, CH3SH2+, CH3SCH2+, S2+, CH2S2+, and CH2S2H+, were measured; their branching ratios as a function of photon energy were derived. Ionization energy of 8.20±0.04eV for CH3SSCH3 and the appearance energy for each fragment ion were determined from the onsets of the photoionization efficiency spectra. Based on the appearance energy and existing thermochemical data, plausible structures of the fragment ions and their neutral counterparts are proposed. Fragmentation mechanisms that involve H migration and structural rearrangement in the dissociative photoionization processes are discussed.
Thermal energy reactions of CO2+ with chloromethanes
Tsuji, Masaharu,Funatsu, Tsuyoshi,Matsumura, Ken-ichi,Nishimura, Yukio
, p. 4526 - 4532 (2007/10/02)
Rate constants and product ions have been determined for thermal energy reactions of CO2+ with CHnCl4-n (n = 0-3) by using an ion-beam apparatus.Total rate constants are (8.7+/-3.7), (6.7+/-3.1), (9.1+/-4.1), and (4.9+/-1.6)x10-10 cm3 s-1 for CH3Cl, CH2Cl2, CHCl3, and CCl4, respectively.These values amount to 38percent-61percent of the collision rate constants estimated from either the Langevin or averaged dipole oriented theory.Although charge transfer followed by the successive loss of a Cl atom is the major product channel, parent ions are formed from CH3Cl and CH2Cl2 with branching ratios of 33percent+/-5percent and 25percent+/-3percent, respectively.The reaction mechanisms are interpreted in terms of the electronic states of the parent molecular ion accessible in the charge-transfer processes.The lack of formation of parent ions from CHCl3 and CCl4 is explained as due to complete (pre)dissociation of ionic states below 13.78 eV.
Translational Energy-Resolved Collisionally Activated Methyl Cation Transfer from Protonated Methane to Argon, Krypton, and Xenon and from Protonated Fluoromethane to Argon and Molecular Oxygen
Heck, Albert J. R.,Koning, Leo J. de,Nibbering, Nico M. M.
, p. 8870 - 8876 (2007/10/02)
Translational energy-resolved collisionally activated gas-phase reactions of protonated methane with argon, krypton, and xenon and of protonated fluoromethane with argon and molecular oxygen are studied using the method of Fourier transform ion cyclotron resonance mass spectrometry.It appears that translationally activated protonated methane can act as a methyl cation donor if the competing proton transfer is energetically less favored.Translational energy-resolved collisionally activated reactions between protonated methane and argon, krypton, and xenon reveal that the methyl cation transfers resulting in the formation of methylargonium, methylkryptonium, and methylxenium ions all proceed via transition states which are about 0.6 eV higher in energy than the reactants.The results suggest that in these transition states the weakening of the two-electron three-center C-H-H bond in protonated methane is more advanced than the bond formation between the methyl group and the noble gas atom.Similarly, translationally activated protonated fluoromethane can transfer a methyl cation to argon and molecular oxygen via transition states which are about 0.3 and 0.4 eV higher in energy than the reactants, respectively.It is shown that the product ion from the methyl cation transfer from protonated fluoromethane to molecular oxygen has the methylperoxy cation structure.
Photodissociation of Alkyl Nitrites in a Molecular Beam. Primary and Secondary Reactions
Effenhauser, C. S.,Felder, P.,Huber, J. Robert
, p. 296 - 302 (2007/10/02)
The translational energy distributions P(ET) for the 248-nm photodissociation products (NO + RO) of isopropyl nitrite and tert-butyl nitrite have been measured with a molecular beam time-of-flight (TOF) apparatus.Previous experiments with methyl nitrite and ethyl nitrite have been repeated with higher resolution.The average photofragment translation energies of these four alkyl nitrites are in good agreement with those predicted by an impulsive model that treats the NO as a rigid fragment and the alkoxy radical as a soft fragment.Hence, and in contrast to the vibrational predissociation on the S1 potential energy surface, S2 dissociation is direct and involves no significant "vibrational-translational" coupling between the reaction coordinate rO-N and the rN=O coordinate.The width of the experimental P(ET) distributions decreases with increasing size of the alkoxy substituent.This result is discussed in terms of an anticorrelation between the internal energies of a fragment pair.Furthermore, the spontaneous secondary dissociation of isopropoxy and tert-butoxy photofragments was observed which yields CH3 radicals and acetaldehyde or acetone, respectively.The unimolecular decay of these alkoxy radicals confirms their relatively high internal energy as deduced from the primary P(ET) and it is shown that this decay occurs on a submicrosecond time scale.
State selected ion-molecule reactions by a TESICO technique. X. O+(ν) + CH4
Tanaka, Kenichiro,Kato, Tatsuhisa,Koyano, Inosuke
, p. 750 - 755 (2007/10/02)
Vibrational state selected (relative) reaction cross sections have been determined for ν=4-3 of the O2+ ion, for each of the three product channels of the reaction O2+(ν) + CH4, viz.O2+ (ν) + CH4 -> CH3O2+ + H ( 1 ) -> CH3+ + HO2 ( 2 ) -> CH4+ + O2, ( 3 ) using the TESICO (threshold electron-secondary ion coincidence) technique.At a fixed collision energy of 0.27 eV, it has been found that the cross section of exoergic channel ( 1 ) increases most prominently with increasing vibrational quantum number ν in the range ν = 0-2, but decreases sharply in going from ν = 2 to ν = 3.The cross sections of endoergic channels ( 2 ) and ( 3 ) also increase with increasing ν but their rates of increase are much smaller than that of channel ( 1 ) in the range ν = 0-2.When ν is increased to 3, however, charge transfer channel ( 3 ) is enhanced dramatically and the CH4+ ion becomes the most abundant product ion.The cross section of channel ( 2 ) also increases more sharply in going from ν = 2 to ν = 3 than in the range ν = 0-2, but the CH3+ ion still remains the least abundant of the three product ions.As a result of these variations in the individual cross sections, the overall cross section for the O2+ + CH4 reaction increases monotonically with increasing ν throughout the range studied (ν = 4-3) .The results are compared with that of the collision energy dependence as obtained in drift and flow- drift experiments and the implications are discussed in conjunction with the structure of the CH3O2+ ion and the relevant potential energy surfaces.
MAGNITUDE AND ORIGIN OF THE beta -SILICON EFFECT ON CARBENIUM IONS.
Wierschke,Chandrasekhar,Jorgensen
, p. 1496 - 1500 (2007/10/02)
Ab initio molecular orbital calculations have been carried out on alpha - and beta -substituted methyl and vinyl cations to obtain a quantitative measure of the substituent effect of a silyl group relative to a methyl group and hydrogen. Geometries optimized with the 3-21G **(***) basis set were used in calculations at the MP3/6-31G* level. The stabilization energies due to various substituents were determined by means of isodesmic reactions involving the parent methyl and classical vinyl cations. alpha -Methyl substitution of the methyl cation leads to a stabilization energy of 34. 0 kcal/mol compared to 17. 8 kcal/mol obtained through alpha -silyl substitution. The stabilization due to alpha -methyl and alpha -silyl groups is comparable for the vinyl cation (27. 2 and 24. 1 kcal/mol), suggesting that the inductive effect of silicon is more effective in this case.
