14604-48-9Relevant articles and documents
Ion - Molecule Reaction Studies of Hydroxyl Cation and Ionized Water with Ethylene
Fishman, Vyacheslav N.,Grabowski, Joseph J.
, p. 4879 - 4884 (1999)
Rate coefficients and product branching ratios for the ion - molecule reactions of the hydroxyl cation, ionized water, and their deuterated analogues with ethylene have been determined using a selected ion flow tube (SIFT) at room temperature and in 0.5 Torr of helium buffer gas. In all cases, reactions proceed at or near the collision rate. The major product is always charge transfer: 79% for L2O?+and 66% for LO+ and does not depend on the isotopic form of hydrogen present (L = H or D). For the L2O?+ reactions, the remaining 21% of products are from proton or deuteron transfer, with no evidence of an isotope effect on this step even in the HOD?+ reaction. The greater exothermicity of the initial charge transfer in the LO+ reaction is revealed by the observation of additional product channels, forming the vinyl cation and protonated carbon monoxide. Multistep mechanisms that proceed through rate-determining charge-transfer, followed by a product-determining step, are postulated to explain these observations.
Vibrationally resolved inelastic scattering and charge transfer in H+-C2H4 collisions
Aristov, N.,Maring, W.,Niedner-Schatteburg, G.,Toennies, J. P.,Chiu, Y.-N.,Koeppel, H.
, p. 2682 - 2694 (1993)
Differential cross sections and time-of-flight spectra have been measured in a crossed molecular beam apparatus for inelastic scattering and charge transfer in collisions of 30 eV protons with ethylene.High resolution inelastic time-of-flight spectra reveal peaks corresponding to the fundamentals of at least two of the infrared active antisymmetric vibrational modes of ethylene.In the time-of-flight spectra of H atoms resulting from charge transfer energy loss, peaks corresponding to excitation of two electronic states of the ethylene molecular ion are resolved.The H-atom product angular distributions are consistent with a 2.0 eV potential well in the ground state potential energy surface of the charge transfer reaction.The observations for the antisymmetric vibrational modes are explained in terms of an ion-induced dipole mechanism.Excitation of the symmetric modes is attributed to a vibronic coupling mechanism.An appendix provides a detailed account of the vibronic distributions in idealized low energy, high symmetry collisions leading to stable C2H5+ complexes.
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.
Ion-Molecule Reactions of CF3+ with Simple Unsaturated Aliphatic Hydrocarbons at Near-Thermal Energy
Tsuji, Masaharu,Aizawa, Masato,Nishimura, Yukio
, p. 3195 - 3200 (2007/10/02)
Ion-molecule reactions of CF3+ with C2H2, C2H4, and C3H6 have been studied at near-thermal energy (0.05 eV) by using an ion beam apparatus.Initial product ion distributions and reaction rate constants were determined and compared with previous beam and selected ion flow tube (SIFT) data.The CF3+/C2H2 reaction produces exclusively the electrophilic adduct C3H2F3+ ion.For C2H4 and C3H6, hydride abstraction and electrophilic addition followed by HF elimination or fluoride transfer occur in parallel.The branching ratios of the former and latter reactions are 0.29 +/- 0.04:0.71 +/- 0.06 for the CF3+/C2H4 reaction and 0.07 +/- 0.02:0.93 +/- 0.07 for the CF3+/C3H6 reaction.On the basis of theoretical calculations of potential energies for the CF3+/C2H2 and CF3+/C2H4 systems, the lack of the HF elmination channel in the CF3+/C2H2 reaction, whereas the lack of the initial adduct ion in the CF3+/C2H4 reaction, is attributed to the different stability of the intermediate adduct ions for HF elimination.The reaction rate constants were 0.45 x 1E-9, 1.3 x 1E-9, and 1.6 x 1E-9 cm3 s-1 for C2H2, C2H4, and C3H6, respectively, which correspond to 46percent, 120percent, and 130percent of calculated rate constants from Langevin theory or a parametrized trajectory model.Although there are significant discrepancies in the product ion distributions between the present beam experiment and the previous beam data, the product ion distributions and the reaction rate constants obtained here are in reasonable agreement with the previous SIFT data.
Selected-ion flow tube studies of reactions of the carbene cation :C4N+ and their implications for interstellar gas cloud chemistry
Bohme, Diethard K.,Wlodek, Stanislaw,Baksit, Asit B.
, p. 1563 - 1567 (2007/10/02)
The carbene cation :C4N+ was generated in a Selected-Ion Flow Tube (SIFT) apparatus from allyl cyanide by electron impact and related at room temperature in helium buffer gas at ca. 0.33 mm Hg with the molecules H2, CO, HCN, CH4, CD4, H2O, HC3N, C2H2, CH3CN, CD3CN, H2S, NH3, ND3, and C4H2.The reactions were observed to exhibit a range in reactivity and a variety of reaction products.The observed products are consistent with expectations based on the carbene caracter of :C4N+.The results have implications for the role of :C4N+ as a reaction intermediate in the chemistry of interstellar gas clouds.Possible synthetic routes indicated by :C4N+ are proposed for the formation of dicyanoacetylene, cyanodiacetylene, and several acyclic as well as cyclic neutral carbenes.
Selected-ion flow tube studies of reactions of the radical cation (HC3N)+. in the interstellar chemical synthesis of cyanoacetylene
Fox, A.,Raksit, A. B.,Dheandhanoo, S.,Bohme, D. K.
, p. 399 - 403 (2007/10/02)
The radical cation (HC3N)+. was produced in a Selcted-Ion Flow Tube (SIFT) apparatus from cyanoacetylene by electron impact and reacted at room temperature in helium buffer gas with a selection of molecules including H2, CO, HCN, CH4, H2O, O2, HC3N, C2H2, OCS, C2H4, and C4H2.The observed reactions exhibited a wide range of reactivity and a variety of pathways including charge transfer, hydrogen atom transfer, proton transfer, and association.Association reactions were observed with CO, O2, HCH and HC3N.With the latter two molecules association was observed to proceed close to the collision limit, which is suggestive of covalent bond formation perhaps involving azine-like N-N bonds.For HC3N an equally rapid association has been observed by Buckley et al. with ICR (Ion Cyclotron Resonance) measurements at low pressures and this is suggestive of radiative association.The hydrogen atom transfer reaction of ionized cyanoacetylene with H2 is slow while similar reactions with CH4 and H2O are fast.The reaction with CO fails to transfer a proton.These results have implications for synthetic schemes for cyanoacetylene as proposed in recent models of the chemistry of interstellar gas clouds.Proton transfer was also observed to be curiously unfavourable with all other molecules having a proton affinity higher than (C3N)..Also, hydrogen-atom transfer was inefficient with the polar molecules HCN and HC3N.These results suggest that informations at close separations may lead to preferential alignment of the reacting ion and molecule which is not suited for proton transfer or hydrogen atom transfer.
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.
The Study of Ion-Molecule Reactions in the Gas Phase using a Triple Quadrupole Mass Spectrometer. Part 1. The Reactions of CH3+, CD3+, and C2H5+ with Simple Olefins
Batey, Jonathan H.,Tedder, John M.
, p. 1263 - 1268 (2007/10/02)
A triple quadrupole mass spectrometer has been used to study the reactions of simple carbocations with low molecular weight olefins in the gas phase at relatively high pressures (1E-3-1E-4 Torr).In each case a high energy 'addition complex' is formed which fragments spontaneously to give daughter ions, the extent of fragmentation depending to some extent on the pressure and on the translational energy of the primary ions.Also formed are 'second generation' ions due to reactions of the predominant daughter ions with the olefin.Ions with the same mass as the high energy 'addition complexes' have been fragmented by collision (C.I.D.) with inert molecules (N2) to yield similar daughter ions to those found from the 'addition complexes'.In the reactions, involving CD3+ ions, deuterium is widely, but not completely randomly, distributed among the daughter ions.
