463-49-0Relevant articles and documents
Crossed-beam reaction of carbon atoms with hydrocarbon molecules. I. Chemical dynamics of the propargyl radical formation, C3H3 (X2B2), from reaction of C(3Pj) with ethylene, C2H4(X1/Ag)
Kaiser,Lee,Suits
, p. 8705 - 8720 (1996)
The reaction between ground-state carbon atoms, C(3Pj), and ethylene, C2H4(X1Ag), was studied at average collision energies of 17.1 and 38.3 kJmol-1 using the crossed molecular beams technique. Product angular distributions and time-of-flight spectra of m/e=39 were recorded. Forward-convolution fitting of the results yields a maximum energy release as well as angular distributions consistent with the formation of the propargyl radical in its X2B2 state. Reaction dynamics inferred from the experimental data indicate two microchannels, both initiated by attack of the carbon atom to the π-orbital of the ethylene molecule via a loose, reactant like transition state located at the centrifugal barrier. Following Cs symmetry on the ground state 3A″ surface, the initially formed triplet cyclopropylidene complex rotates in a plane roughly perpendicular to the total angular momentum vector around its C-axis, undergoes ring opening to triplet allene, and decomposes via hydrogen emission through a tight transition state to the propargyl radical. The initial and final orbital angular momenta L and L′ are weakly coupled and result in an isotropic center-of-mass angular distribution. A second microchannel arises from A-like rotations of the cyclopropylidene complex, followed by ring opening and H-atom elimination. In this case, a strong L-L′ correlation leads to a forward-scattered center-of-mass angular distribution. The explicit identification of C3H3 under single collision conditions represents a single, one-step mechanism to build up hydrocarbon radicals. Our findings strongly demand incorporation of distinct product isomers of carbon atom-neutral reactions in reaction networks simulating chemistry in combustion processes, the interstellar medium, as well as in outflows of carbon stars, and open the search for the hitherto unobserved interstellar propargyl radical.
Isomerization of Cyclopropene to Allene and Propyne at Elevated Temperatures. Experimental, ab Initio, and Model Calculations
Karni, M.,Oref, I.,Barzilai-Gilboa, S.,Lifshitz, A.
, p. 6924 - 6929 (1988)
Results of an experimental and theoretical investigation of the isomerization of cyclopropene to propyne and allene are reported.Shock tube experiments were carried out over the temperature range 800-1200 K, and ratios of / at different temperatures and pressures were measured.Ab initio calculations were done, from which energy levels and vibrational frequencies of two transition states were evaluated.RRKM and absolute rate theory calculations based on these parameters produced the following high-pressure rate coefficients (at 800 K): k1=1013.42exp(-65.1x103/RT) s-1, k2=1013.85exp(-43.7x103/RT) s-1, k3=1014.03exp(-70.8x103/RT) s-1, and k4=1014.18exp(-50.4x103/RT) s-1, where R is expressed in units of cal/(K mol).RRKM calculated rate coefficients were used to compute ratios of / at different temperatures and pressures and to compare them with the experimental results.A very good agreement between experiment and theory is obtained.
Ca12InC13- x and Ba12InC18H4: Alkaline-earth indium allenylides synthesized in AE/Li flux (AE = Ca, Ba)
Blankenship, Trevor V.,Dickman, Matthew J.,Van De Burgt, Lambertus J.,Latturner, Susan E.
, p. 914 - 921 (2015)
Two new complex main-group metal carbides were synthesized from reactions of indium, carbon, and a metal hydride in metal flux mixtures of an alkaline earth (AE = Ca, Ba) and lithium. Ca12InC13-x and Ba12InC18H4 both crystallize in cubic space group Im3 [a = 9.6055(8) and 11.1447(7) ?, respectively]. Their related structures are both built on a body-centered-cubic array of icosahedral clusters comprised of an indium atom and 12 surrounding alkaline-earth cations; these clusters are connected by bridging monatomic anions (either H- or C4-) and allenylide anions, C34-. The allenylide anions were characterized by Raman spectroscopy and hydrolysis studies. Density of states and crystal orbital Hamilton population calculations confirm that both compounds are metallic.
THERMAL AND PHOTOCHEMICAL DEAZETATIONS OF FLUORINE-SUBSTITUTED 4-METHYLENEPYRAZOLINES. THE KINETIC BEHAVIOR OF TRIMETHYLENEMETHANES.
Dolbier Jr.,Burkholder
, p. 2139 - 2142 (1984)
4-(Difluoromethylene)-1-pyrazoline and 4-(fluoromethylene)-1-pyrazoline were observed to undergo thermal and photochemical deazetation in the gas phase as well as in solution to form mixtures of methylenecyclopropanes. The gas-phase and solution-phase, thermal, and photochemical results are contrasted, and the observed kinetically controlled product ratios are compared with the very different equilibrium values. As a result, mechanisms involving trimethylenemethane diradicals are proposed for both processes. The photochemical reactions seem to be dominated by 'hot' reactions of vibrationally excited TMMs, while the thermal reactions show interesting selectivity in their cyclization processes.
Propyne Pyrolysis in a Flow Reactor: An Experimental, RRKM, and Detailed Kinetic Modeling Study
Davis, Scott G.,Law, Chung K.,Wang, Hai
, p. 5889 - 5899 (1999)
The pressure-dependent rate coefficients for several reactions relevant to propyne pyrolysis were determined with ab initio quantum mechanical calculations and Rice - Ramsperger - Kassel - Marcus (RRKM) analyses. These reactions include the mutual isomerization of propyne and allene, the chemically activated reactions of propyne and allene with the H atom and of acetylene with methyl on the C3H5 potential energy surface. Propyne pyrolysis was experimentally studied in a flow reactor at 1210 K and 1 atm. A detailed reaction mechanism, employing the current RRKM rate coefficients, is shown to accurately predict the experimental acetylene and methane profiles determined in the flow reactor and literature shock-tube data of propyne and allene pyrolysis up to 1500 K.
Unsaturated Ketenes: A Study of their Formation and Rearrangement by Tandem Mass Spectrometry and Low-temperature Infrared Spectroscopy
Maquestiau, Andre,Pauwels, Pascal,Flammang, Robert,Lorencak, Primoz,Wentrup, Curt
, p. 259 - 266 (1986)
A combination of collisional activation mass spectrometry and low-temperature infrared spectroscopy has been used to monitor the production and isomerization of vinyl- and methylene-ketenes.Vinyl- and 2-propenyl-ketenes were produced by flash vacuum pyrolysis of β,γ-unsaturated acid chlorides.Vinyl(carboxyl)ketenes, vinylketenes and methyleneketenes were obtained from Meldrum's acid derivatives (5-alkylidene-1,3-dioxane-4,6-diones).The formation of methyleneketenes by pyrolysis of α,β-unsaturated acid chlorides is only indicated in the mass spectrometry experiments.Carbonylcyclopropane was obtained by pyrolysis of cyclopropylcarbonyl chloride or the corresponding Meldrum's acid derivative.The methyleneketenes isomerize to vinylketenes in the gas phase, particularly under conditions involving long contact times.Carbonylcyclopropane thermally decarbonylates to allene, not methylacetylene.Molecular ions of vinylketenes are obtained via pyrolysis of either acid chlorides or Meldrum's acid derivatives.Molecular ions of alkylmethyleneketenes are obtained pure only by electron impact induced fragmentation of Meldrum's acid derivatives.
On the photodissociation of propadienylidene, l-C3H2
Gross, Christoph,Noller, Bastian,Fischer, Ingo
, p. 5196 - 5201 (2008)
We investigate the photochemistry and photodissociation dynamics of the linear C3H2 isomer propadienylidene by two-colour photofragment Doppler spectroscopy at excitation wavelengths between 260 and 230 nm, corresponding to excitatio
Single-molecule chemistry and analysis: Mode-specific dehydrogenation of adsorbed propene by inelastic electron tunneling
Parschau, Manfred,Rieder, Karl-Heinz,Hug, Hans J.,Ernst, Karl-Heinz
, p. 5689 - 5691 (2011)
A single propene molecule, located in the junction between the tip of a scanning tunneling microscope (STM) and a Cu(211) surface can be dehydrogenated by inelastic electron tunneling. This reaction requires excitation of the asymmetric C-H stretching vibration of the =CH2 group. The product is then identified by inelastic electron tunneling action spectroscopy (IETAS).
Effect of Central Substituents on the Gas-Phase Acidities of Propenes
Bartmess, John E.,Burnham, Robert D.
, p. 1382 - 1387 (1984)
The gas-phase acidities of a number of 2-substituted propenes have been measured by using ICR spectrometry.The acidities are rationalized in terms of structural effects on both acid and anion forms.MNDO calculations reproduce the acidities to +/-4.2 kcal/mol and provide information on the interaction of the ? orbitals of substituent and acid.
Thermal decomposition of 2-bromopropene, and 2-chloropropene
Roy, Karin,Awan, Iftikhar A.,Manion, Jeffrey A.,Tsang, Wing
, p. 1806 - 1810 (2003)
2-Chloropropene and 2-bromopropene have been decomposed in single pulse shock tube experiments. The only products under all conditions are propyne and allene. The high pressure rate expressions are k(2-BrC3H5 propyne/allene + HBr) =
