- Deuteration and dimerization of acetylene with a nieuwland catalyst in deuterium oxide
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Efficient deuteration and dimerization of acetylene have been readily attained in deuterium oxide with a Nieuwland catalyst which is practically used for dimerization of acetylene. Copyright
- Tachiyama, Takashi,Yoshida, Makoto,Aoyagi, Tatsuhiro,Fukuzumi, Shunichi
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- Site and isotope effects on the molecular hydrogen elimination from ethylene at 157 nm excitation
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Site and isotope effects on the molecular hydrogen elimination from ethylene have been studied from the photodissociation of ethylene at 157 nm excitation. Experimental results show that there are three different types of molecular elimination processes: 1,1 elimination, 1,2-cis elimination, and 1,2-trans elimination. These elimination processes show significantly different translational energy distributions. Isotope effect on the dynamics of these molecular hydrogen elimination processes has been also investigated carefully.
- Lin, Jim J.,Hwang, Dennis W.,Lee, Yuan T.,Yang, Xueming
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p. 2979 - 2982
(2007/10/03)
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- Photochemistry of Hydrogen Bromide-Acetylene Complexes in Solid Krypton
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Hydrogen-bonded complexes between HBr and acetylene in inert gas matrices were subjected to medium-pressure Hg lamp photolysis at 12 K.For HBr-acetylene, the major product was bromoacetylene, while vinyl bromide was present in trace amounts.When HBr-perdeuterioacetylene and DBr-acetylene complexes were photolyzed, bromoacetylene, deuteriobromoacetylene, and the hydrogen exchange product, DBr(HBr)-C2HD, were the primary products.Partially deuterated vinyl bromides were present in trace amounts.In HBr-perdeuterioacetylene, the only isomer observed was cis-CDBr=CHD.In DBr-acetylene, both cis- and trans-CHBr=CHD were observed.In neither experiment was the 1,1-addition product formed.The results are interpreted in terms of the supramolecule model of complex photochemistry put forth by Abrash and Pimentel.
- Abrash, Samuel A.,Carr, Celia M.,McMahon, Michael T.,Zehner, Robert W.
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p. 11909 - 11917
(2007/10/02)
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- Comparison of bending, C-C stretching, and collision energy effects on the reaction of C2H2+ with D2
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We report the effects of vibrational excitation and collision energy on the cross sections and branching ratios for reaction of acetylene cations with D2, using two different guided-ion-beam instruments.Two major reaction channels are observed, both of which are nearly thermoneutral.Hydrogen atom exchange is slightly exoergic due to zero point energy, and is inhibited by both collision and vibrational energy.Formation of the two isotopic C2H3+ products is enhanced by collision energy and C-C stretching vibration, but not by bending vibration.The branching ratios at low collision energies are consistent with reaction via an intermediate complex, and Rice-Ramsberger-Kassel-Marcus (RRKM) analysis is used to extract further information.At collision energies above 1 eV, D-atom transfer by a direct mechanism is also observed as a route to C2H2D+ production.Comparison of our results using both the Stony Brook and Freiburg instruments is made with the state-selected experiments of Honma, Kato, Tanaka, and Koyano , who previously studied both the C2H2+ + D2 and C2D2+ + H2 isotopic reactants.Our results for C2H2+ + D2 are consistent with their C2D2+ + H2 data for all collision energies and with their C2H2+ + D2 data at 0.2 eV collision energy.We do not reproduce the anomalous vibrational effects they reported for 1 and 2 eV collision energies.
- Chiu, Yu-hui,Yang, Baorui,Fu, Hungshin,Anderson, Scott L.,Schweizer, Martin,Gerlich, Dieter
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p. 5781 - 5788
(2007/10/02)
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- Photodissociation of Methylacetylene at 193 nm
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The photolysis of methylacetylene (MA) at 193 nm was studied using Fourier transform infrared spectroscopy for product analysis.Main primary processes are CH3C2H + h*ν -> CH3C2 + H and CH3C2H + h*ν -> CH2 + C2H2 with a quantum yield of 0.7 +/- 0.1 and 0.11 +/- 0.01, respectively.Cl2 was used as H atom scavenger.The CD3C2H photolysis was used to confirm that acetylene-d1 formed is a primary product and is independent of reactant pressures.The H atom addition to the center carbon atom of CD3C2H produces CD3 + C2H2 with a yield of 0.10 +/- 0.01; C2H2 is reduced to almost zero above 5 Torr of MA.The remaining H atom addition to the end carbon would produce allene and propylene.The photolysis of CD3C2H and Cl2 mixtures produces only HCl and DCl is not found, indicating that H atoms are dissociated immediately from the triple-bonded carbon, although the C-D bond in CD3C2H is much weaker.
- Seki, Kanekazu,Okabe, Hideo
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p. 3345 - 3349
(2007/10/02)
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- Photochemistry of Hydrogen Iodide-Acetylene Complexes in Solid Krypton
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Hydrogen iodide-acetylene complexes in a krypton matrix at 12 K have been photolyzed with a medium-pressure mercury lamp.Infrared spectra identify products vinyl iodide and iodoacetylene.When HI*C2D2 complexes are photolyzed, isotopic exchange occurs to produce DI*HCCD.Growth curves show that all three are primary products.As well, the growth curves show secondary photolysis of vinyl iodide and DI*HCCD, but apparently production and secondary photolysis of vinyl iodide only catalyze isotopic exchange.The growth curves obtained for HCCI and DCCI from HI*C2D2 differ from those obtained from DI*C2H2.Short photolysis of HI*C2D2 gives almost exclusively HD*DCCI whereas short photolysis of DI*C2H2 gives HD*HCCI.Thus the hydrogen atom in the hydrogen iodode always ends up in the molecular hydrogen product.We conclude that photolytic production of iodoacetylene involves hydrogen atom abstraction from acetylene by the energetic hydrogen iodide.
- Abrash, Samuel A.,Pimentel, George C.
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p. 5828 - 5834
(2007/10/02)
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- Photochemistry of Diacetylene
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Adsorption coefficients of C4H2 have been measured in the 183-260-nm wavelength region.The photochemistry of diacetylene has been studied at 147.0, 184.9, 228.8, and 253.7 nm.The primary dissociative processes at 147 nm, deduced from the photolysis of C4H2 and D2 mixtures, are, in order of decreasing importance, C4H2 + hν -> C4H + H, C4H2 + hν -> C2H2 + C2, and C4H2 + hν -> 2C2H with quantum yields of 0.2, 0.1, and 0.03, respectively.In addition, the quantum yields of products and of reactant disappearance were measured in neat C4H2 and C4H2 and N2 mixtures.It is concuded that (1) reactions involving metastable excited states, C4H2** + C4H2 -> C8H2 + H2, are the main disappearance processes at three other wavelengths and (2) the C4H2** sates are stable toward collisions with N2.The excited-state reactions may be the predominant photochemical processes of C4H2 in Titan's stratosphere.
- Glicker, S.,Okabe, H.
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p. 437 - 440
(2007/10/02)
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- INTERNAL ROTATION AND FRAMEWORK RELAXATION IN ETHENE THIOL
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New and existing data on the ground and excited CS torsional states of the stable rotamers of ethene thiol have been analysed to give a potential function for internal rotation around the CS bond.The barrier between the syn and anti rotamers is found to be 800 cm-1 and that at the planar anti conformation itself to be 12 cm-1.The syn conformation is 50 cm-1 more stable than the 'quasi-planar' anti conformation.Satisfactory reproduction of the observed trends in rotational constants with torsional excitation has been achieved by introducing extensive relaxation of the CCS angle and the CS bond length during internal rotation.The CCS angle reduces by up to 5 deg whilst the CS bond length increases by up to 0.02 Angstroem during rotation from the syn to anti conformation.The use of ab initio M.O. calculations to provide an indication of the most significant aspects of structure relaxation is described.
- Almond,V.,Permanand, R. R.,Macdonald, J. N.
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p. 337 - 352
(2007/10/02)
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- Structure of the Bromovinyl Radical: a Matrix Isolation Study
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The bromovinyl radical has been prepared by the reaction of bromine atoms with acetylene in an argon matrix at 17 K and its i.r. spectrum has been studied.The spectrum of C2HDBr. shows the presence of two isomers, indicating that the radical has an unsymmetric structure.
- Engdahl, Anders,Nelander, Bengt
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p. 1747 - 1750
(2007/10/02)
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- Photodissociation at 193 nm of Cyclooctatetraene and Styrene into Benzene and Acetylene
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When irradiated in a molecular beam at 193 nm, both cyclooctatetraene and styrene dissociate into benzene and acetylene.The average kinetic energy release is 12percent of the available energy in both cases.So that the mechanism of the dissociation of styrene could be determined the ratio of mass 26 to mass 27 (C2H2/C2HD) was measured for C6H5CDCH2 and C6H5CHCH2 and found to be 1.46 +/- 0.10 and 2.29 +/- 0.10, respectively.These numbers rule out cyclooctatetraene as an intermediate in the dissociation of styrene.A bicycloocta-2,4,7-triene intermediate which can tautomerize by 1,3 hydrogen atom jumps in the smaller ring explains all the experimental results.
- Yu, C. F.,Youngs, F.,Bersohn, R.,Turro, N. J.
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p. 4409 - 4412
(2007/10/02)
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- Catalytic Activities of Organic Polymer-Quinone Complexes. - I. Hydrogen Exchange Reaction between Acetylene and Polyvinylpyridine-Quinone Complexes
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The hydrogen exchange reaction between acetylene (C2D2) and the complexes of various aromatic quinones with organic vinylpolymers was studied.There existed a multiple exchange process and a considerable amount of C2H2 was formed from the beginning of the exchange reaction.Catalytic C2H2-C2D2 exchange reaction was also examined on these complexes and it was concluded that this reaction proceeds through the hydrogen of the complex. - Keywords: Acetylene / Hydrogen / Exchange / Polymer-quinone complexes
- Naito, Shuichi,Tamaru, Kenzi
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p. 243 - 246
(2007/10/02)
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- CO2 LASER-INDUCED DECOMPOSITION OF METHYL IODIDE SENSITIZED BY SULFUR HEXAFLUORIDE
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Gaseous mixtures of methyl iodide and sulfur hexafluoride yield upon irradition by a continuous-wave CO2 laser iodine, methane, ethane, ethylene and acetylene - the products of methyl iodide decomposition.The decomposition rate and the mutual ratio of the products is dependent on the delivered irradiatiion energy, the methyl iodide/sulfur hexafluoride ratio and the energy of the exciting photon.Methyl iodide-d3 in the mixture with SF6 behaves similarly as methyl iodide yielding perdeuterated methane, ethane, ethylene, acetylene and iodine.
- Dathe, Klaus,Engst, Pavel,Pola, Josef,Horak, Milan
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p. 1910 - 1919
(2007/10/02)
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