- 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)
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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.
- Kaiser,Lee,Suits
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- Isomerization of Cyclopropene to Allene and Propyne at Elevated Temperatures. Experimental, ab Initio, and Model Calculations
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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.
- Karni, M.,Oref, I.,Barzilai-Gilboa, S.,Lifshitz, A.
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- Ca12InC13- x and Ba12InC18H4: Alkaline-earth indium allenylides synthesized in AE/Li flux (AE = Ca, Ba)
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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.
- Blankenship, Trevor V.,Dickman, Matthew J.,Van De Burgt, Lambertus J.,Latturner, Susan E.
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- THERMAL AND PHOTOCHEMICAL DEAZETATIONS OF FLUORINE-SUBSTITUTED 4-METHYLENEPYRAZOLINES. THE KINETIC BEHAVIOR OF TRIMETHYLENEMETHANES.
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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.
- Dolbier Jr.,Burkholder
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- Propyne Pyrolysis in a Flow Reactor: An Experimental, RRKM, and Detailed Kinetic Modeling Study
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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.
- Davis, Scott G.,Law, Chung K.,Wang, Hai
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- Unsaturated Ketenes: A Study of their Formation and Rearrangement by Tandem Mass Spectrometry and Low-temperature Infrared Spectroscopy
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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.
- Maquestiau, Andre,Pauwels, Pascal,Flammang, Robert,Lorencak, Primoz,Wentrup, Curt
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- On the photodissociation of propadienylidene, l-C3H2
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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
- Gross, Christoph,Noller, Bastian,Fischer, Ingo
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- Single-molecule chemistry and analysis: Mode-specific dehydrogenation of adsorbed propene by inelastic electron tunneling
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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).
- Parschau, Manfred,Rieder, Karl-Heinz,Hug, Hans J.,Ernst, Karl-Heinz
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- Effect of Central Substituents on the Gas-Phase Acidities of Propenes
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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.
- Bartmess, John E.,Burnham, Robert D.
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- Thermal decomposition of 2-bromopropene, and 2-chloropropene
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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) =
- Roy, Karin,Awan, Iftikhar A.,Manion, Jeffrey A.,Tsang, Wing
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- Photoelectron angular distribution parameters of valence shell ionizations of allene and transient ketene and thioketene
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Photoelectron angular distribution parameters for the X2E ionization of allene and, for the first time, for ionizations of reaction intermediates, namely the X2B1 ionization of ketene and the X2B1, A2B2 and B2B1 ionizations of thioketene have been measured using synchrotron radiation up to photon energies of 23.0, 20.0 and 19.5 eV, respectively.The β curves exhibit several structures which could stem from resonance phenomena.Indications of an autoionization resonance were found in the X2E ionization of allene and for a shape resonance in the X2B1 ionization of thioketene.
- Kreile, Jurgen,Kurland, Heinz-Dieter,Seibel, Werner,Schweig, Armin
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- Photochemistry of 3-halopropenes in argon matrices
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The photochemistry of 3-chloropropene, 3-bromopropene and 3-iodopropene in argon matrices was investigated using infrared spectroscopy to determine the major products.The primary product was found to be the allene-hydrogen halide complex, with propyne and cyclopropyl halides being produced by secondary photolysis of the allene.
- Barnes, A. J.,Holroyd, S.
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- Reactions of 2,3-dichloro-1-propene with sulfur and tellurium in the system hydrazine hydrate-KOH
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2,3-Dichloro-1-propene reacts with sulfur dissolved in the system hydrazine hydrate-KOH (with formation of K2S2 or K2S) to afford bis(2-chloro-1-propene-3-yl)sulfide as the main product in both cases. Under similar conditions tellurium induces β-elimination of both chlorine atoms resulting in the formation of allene and complete regeneration of tellurium metal.
- Levanova,Grabel'Nykh,Russavskaya,Klyba,Zhanchipova,Albanov,Tarasova,Korchevin
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- Laser-powered Homogeneous Decomposition of Allyl Chloride
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The continuous wawe CO2 laser powered homogeneous decomposition of allyl chloride sensitized by sulphur hexafluoride was examined in order to determine the course of reaction in the absence of wall effects.The elimination of heterogeneous processes simplifies the reaction scheme and leads to the formation only of propyne, propadiene, benzene, and at higher conversions, acetylene.The total yield of propyne and propadiene is three times higher than that in coventional pyrolysis.
- Pola, Josef
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- The gas-phase pyrolysis of 2,2-dinitropropane: Shock-tube kinetics
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The thermal decomposition of 2,2-dinitropropane (DNP) was studied in a shock tube at 970-1200 K, under high dilution in argon at 4.5-5.5 atm. The decay of DNP and the production of NO2 were followed spectrophotometrically at 280 and 405 nm, respectively. The major products were CO, NO, CO2, acetone, CH3C≡H, CH2=C=CH2, CH3CN, CH3OH, CH4, H2O, and CH2O. The first step in the decomposition was C-NO2 bond fission. However, the temporal profiles of NO2 during the decomposition were different from those recorded during the decompositions of CH3NO2 or 2-nitropropane, thus pointing to distinctive features in the mechanism. A complation of 90 elementary steps was proposed. Sensitivity analysis of the mechanism showed that only 57 steps were essential to describe the overall pyrolysis. H,OH, NO2. HCO, and HNO played critical roles in the decomposition.
- Zhang, Yi-Xue,Bauer
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- Unexpected reaction of 2-chloro-1-propen-3-yl isothiuronium chloride with potassium ditelluride: the first example of vicinal elimination of chlorine and sulfur-bearing moieties
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2-Chloro-1-propen-3-yl isothiuronium chloride reacts with potassium ditelluride in hydrazine hydrate to afford elemental tellurium and allene. The latter is formed due to the vicinal elimination of chlorine and a sulfur-bearing moiety.
- Levanova, Ekaterina P.,Grabelnykh, Valentina A.,Elaev, Alexander V.,Albanov, Alexander I.,Klyba, Lyudmila V.,Russavskaya, Natalia V.,Tarasova, Olga A.,Rozentsveig, Igor B.,Korchevin, Nikolai A.
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- Effect of the chalcogen nature on the reaction of propane-1,3- dichalcogenolates with 2,3-dichloroprop-1-ene
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The direction of the reaction of propane-1,3-dichalcogenolates with 2,3-dichloroprop-1-ene in the system hydrazine hydrate-KOH depends not only on the conditions but to a greater extent on the chalcogen nature. Dipotassium propane-1,3-dithiolate and propane-1,3-diselenolate give rise to products of substitution of the chlorine atom on the sp 3-carbon atom, which are capable of undergoing further transformations (domino reaction). Dipotassium propane-1,3-ditellurolate promotes elimination of both chlorine atoms with formation of allene.
- Levanova,Grabel'Nykh,Vakhrina,Russavskaya,Albanov,Klyba,Korchevin,Rozentsveig
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- Isomerization and Selective Hydrogenation of Propyne: Screening of Metal-Organic Frameworks Modified by Atomic Layer Deposition
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Various metal oxide clusters upward of 8 atoms (Cu, Cd, Co, Fe, Ga, Mn, Mo, Ni, Sn, W, Zn, In, and Al) were incorporated into the pores of the metal-organic framework (MOF) NU-1000 via atomic layer deposition (ALD) and tested via high-throughput screening
- Hackler, Ryan A.,Pandharkar, Riddhish,Ferrandon, Magali S.,Kim, In Soo,Vermeulen, Nicolaas A.,Gallington, Leighanne C.,Chapman, Karena W.,Farha, Omar K.,Cramer, Christopher J.,Sauer, Joachim,Gagliardi, Laura,Martinson, Alex B. F.,Delferro, Massimiliano
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p. 20380 - 20389
(2020/11/27)
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- Hydroaminoalkylation of Allenes
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The first examples of early-transition-metal-catalyzed hydroaminoalkylation reactions of allenes are reported. Initial studies performed with secondary aminoallenes led to the identification of a suitable titanium catalyst and revealed that under the reaction conditions, the initially formed hydroaminoalkylation products undergo an unexpected titanium-catalyzed rearrangement to form the thermodynamically more stable allylamines. The assumption that this rearrangement involves a reactive allylic cation intermediate provides a simple explanation of the fact that no successful early-transition-metal-catalyzed hydroaminoalkylations of allenes have previously been reported. As a result of the generation of the corresponding cation, the titanium-catalyzed intermolecular hydroaminoalkylation of propa-1,2-diene unexpectedly gives an aminocyclopentane product formed by incorporation of two equivalents of propa-1,2-diene.
- Bielefeld, Jens,Mannhaupt, Steffen,Schmidtmann, Marc,Doye, Sven
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supporting information
p. 967 - 971
(2019/05/10)
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- Cobalt-Iron-Manganese Catalysts for the Conversion of End-of-Life-Tire-Derived Syngas into Light Terminal Olefins
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Co-Fe-Mn/γ-Al2O3 Fischer–Tropsch synthesis (FTS) catalysts were synthesized, characterized and tested for CO hydrogenation, mimicking end-of-life-tire (ELT)-derived syngas. It was found that an increase of C2-C4 olefin selectivities to 49 % could be reached for 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn/γ-Al2O3 with Na at ambient pressure. Furthermore, by using a 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al2O3 catalyst the selectivity towards the fractions of C5+ and CH4 could be reduced, whereas the selectivity towards the fraction of C4 olefins could be improved to 12.6 % at 10 bar. Moreover, the Na/S ratio influences the ratio of terminal to internal olefins observed as products, that is, a high Na loading prevents the isomerization of primary olefins, which is unwanted if 1,3-butadiene is the target product. Thus, by fine-tuning the addition of promoter elements the volume of waste streams that need to be recycled, treated or upgraded during ELT syngas processing could be reduced. The most promising catalyst (5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al2O3) has been investigated using operando transmission X-ray microscopy (TXM) and X-ray diffraction (XRD). It was found that a cobalt-iron alloy was formed, whereas manganese remained in its oxidic phase.
- Falkenhagen, Jan P.,Maisonneuve, Lise,Paalanen, Pasi P.,Coste, Nathalie,Malicki, Nicolas,Weckhuysen, Bert M.
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supporting information
p. 4597 - 4606
(2018/03/06)
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- Palladium-Catalyzed One-Pot Conversion of Aldehydes and Ketones into 4-Substituted Homopropargyl Alcohols and 5-En-3-yn-1-ols ?
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Sequential treatment of 2,3-dichloropropene with magnesium and n-BuLi generated the equivalent of 1,3-dilithiopropyne, which adds regiospecifically to aldehydes and ketones to produce homopropargyl alcohols. The lithium acetylide intermediate formed in this protocol can be further reacted with aromatic and vinyl halides, under palladium catalysis, to produce 4-substituted homopropargyl alcohols and 5-en-3-yn-1-ols, respectively, in one-pot with good overall yields.
- Umana, Christian A.,Cabezas, Jorge A.
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p. 9505 - 9514
(2017/09/23)
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- Study of the Formation of the First Aromatic Rings in the Pyrolysis of Cyclopentene
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The thermal decomposition of cyclopentene was studied in a jet-stirred reactor operated at constant pressure and temperature to provide new experimental information about the formation of the first aromatic rings from cyclic C5 species. Experim
- Herbinet, Olivier,Rodriguez, Anne,Husson, Benoit,Battin-Leclerc, Frédérique,Wang, Zhandong,Cheng, Zhanjun,Qi, Fei
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p. 668 - 682
(2016/02/23)
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- An acelylenically of a diene compound and/or method of manufacturing
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Provided is a novel method for producing a compound having acetylene bonds and/or a diene. The method for producing a compound having acetylene bonds and/or a diene is characterized in that at least one selected from the group consisting of ketone compound (I), ketone compound (II), aldehyde compound (III), aldehyde compound (IV), and aldehyde compound (V) is dehydrated in the presence of a catalyst wherein a carrier containing silica supports at least one selected from the group consisting of compounds containing group 1 metal elements, compounds containing group 2 metal elements, group 1 metal elements, and group 2 metal elements.
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Paragraph 0371-0375; 0379
(2017/03/28)
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- Pyrolysis of 3-carene: Experiment, Theory and Modeling
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Thermal decomposition studies of 3-carene, a bio-fuel, have been carried out behind the reflected shock wave in a single pulse shock tube for temperature ranging from 920 K to 1220 K. The observed products in thermal decomposition of 3-carene are acetylene, allene, butadiene, isoprene, cyclopentadiene, hexatriene, benzene, toluene and p-xylene. The overall rate constant for 3-carene decomposition was found to be k / s-1 = 10(9.95 ± 0.54) exp (- 40.88 ± 2.71 kcal mol-1/RT). Ab-initio theoretical calculations were carried out to find the minimum energy pathway that could explain the formation of the observed products in the thermal decomposition experiments. These calculations were carried out at B3LYP/6-311 + G(d,p) and G3 level of theories. A kinetic mechanism explaining the observed products in the thermal decomposition experiments has been derived. It is concluded that the linear hydrocarbons are the primary products in the pyrolysis of 3-carene.
- Sharath,Chakravarty,Reddy,Barhai,Arunan
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p. 2119 - 2135
(2016/01/12)
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- METHOD FOR PRODUCING METHACRYLIC ACID ESTER
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The method for producing a methacrylic acid ester of the present invention comprises a dehydration reaction step of having acetone undergo a dehydration reaction in the presence of a dehydration reaction catalyst to obtain a reaction mixture; a propyne/propadiene separation step of separating a mixture containing propyne and propadiene as main components from the obtained reaction mixture; a propyne purification step of separating the separated mixture containing propyne and propadiene as main components into a liquid, gas, or gas-liquid mixture containing propyne as a main component, and a liquid, gas, or gas-liquid mixture containing propadiene as a main component; and a carbonylation reaction step of bringing the obtained liquid, gas, or gas-liquid mixture containing propyne as a main component into contact with carbon monoxide and an alcohol having 1 to 3 carbon atoms in the presence of a catalyst containing at least one selected from the group consisting of Group 8 metal elements, Group 9 metal elements, and Group 10 metal elements to obtain a methacrylic acid ester. According to the method of the present invention, it is possible to provide a method for producing a methacrylic acid ester, which is less likely to receive location restrictions and is also economically and industrially advantageous.
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Paragraph 0104; 0105; 0109; 0110; 0111
(2016/01/25)
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- METHOD FOR PRODUCING COMPOUND AND/OR DIENE HAVING ACETYLENE BOND
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PROBLEM TO BE SOLVED: To provide a method for producing a compound and/or diene having an acetylene bond at high productivity over a long period. SOLUTION: Provided is a method for producing a compound and/or diene having an acetylene bond characterized in that 1) a ketone compound is brought into dehydration reaction in the presence of a catalyst obtained by carrying (A) at least one kind of element selected from the group consisting of the first group elements and the second group elements and at least one kind of element (B) selected from the group consisting of the third group elements, the fourth group elements and the thirteenth elements into a carrier, and also provided the catalyst. COPYRIGHT: (C)2016,JPOandINPIT
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Paragraph 0136; 0137
(2016/10/07)
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- Direct, nonoxidative conversion of methane to ethylene, aromatics, and hydrogen
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The efficient use of natural gas will require catalysts that can activate the first C-H bond of methane while suppressing complete dehydrogenation and avoiding overoxidation. We report that single iron sites embedded in a silica matrix enable direct, nonoxidative conversion of methane, exclusively to ethylene and aromatics. The reaction is initiated by catalytic generation of methyl radicals, followed by a series of gas-phase reactions. The absence of adjacent iron sites prevents catalytic C-C coupling, further oligomerization, and hence, coke deposition. At 1363 kelvin, methane conversion reached a maximum at 48.1% and ethylene selectivity peaked at 48.4%, whereas the total hydrocarbon selectivity exceeded 99%, representing an atom-economical transformation process of methane. The lattice-confined single iron sites delivered stable performance, with no deactivation observed during a 60-hour test.
- Guo, Xiaoguang,Fang, Guangzong,Li, Gang,Ma, Hao,Fan, Hongjun,Yu, Liang,Ma, Chao,Wu, Xing,Deng, Dehui,Wei, Mingming,Tan, Dali,Si, Rui,Zhang, Shuo,Li, Jianqi,Sun, Litao,Tang, Zichao,Pan, Xiulian,Bao, Xinhe
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p. 616 - 619
(2014/05/20)
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- Experimental investigation of the low temperature oxidation of the five isomers of hexane
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The low-temperature oxidation of the five hexane isomers (n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethylbutane, and 2,3-dimethylbutane) was studied in a jet-stirred reactor (JSR) at atmospheric pressure under stoichiometric conditions between 550 and 1000 K. The evolution of reactant and product mole fraction profiles were recorded as a function of the temperature using two analytical methods: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Experimental data obtained with both methods were in good agreement for the five fuels. These data were used to compare the reactivity and the nature of the reaction products and their distribution. At low temperature (below 800 K), n-hexane was the most reactive isomer. The two methyl-pentane isomers have about the same reactivity, which was lower than that of n-hexane. 2,2-Dimethylbutane was less reactive than the two methyl-pentane isomers, and 2,3-dimethylbutane was the least reactive isomer. These observations are in good agreement with research octane numbers given in the literature. Cyclic ethers with rings including 3, 4, 5, and 6 atoms have been identified and quantified for the five fuels. While the cyclic ether distribution was notably more detailed than in other literature of JSR studies of branched alkane oxidation, some oxiranes were missing among the cyclic ethers expected from methyl-pentanes. Using SVUV-PIMS, the formation of C 2-C3 monocarboxylic acids, ketohydroperoxides, and species with two carbonyl groups have also been observed, supporting their possible formation from branched reactants. This is in line with what was previously experimentally demonstrated from linear fuels. Possible structures and ways of decomposition of the most probable ketohydroperoxides were discussed. Above 800 K, all five isomers have about the same reactivity, with a larger formation from branched alkanes of some unsaturated species, such as allene and propyne, which are known to be soot precursors.
- Wang, Zhandong,Herbinet, Olivier,Cheng, Zhanjun,Husson, Benoit,Fournet, Rene,Qi, Fei,Battin-Leclerc, Frederique
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p. 5573 - 5594
(2014/08/18)
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- Reaction of diphenyl ditelluride with 2,3-dichloroprop-1-ene in the system hydrazine hydrate-KOH
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Diphenyl ditelluride reacts with 2,3-dichloroprop-1-ene in the system hydrazine hydrate-KOH along several parallel routes. Beside the nucleophilic chlorine substitution at the sp 3-hybridized carbon atom resulting in 2-chloro-3-phenyltellanylprop-1-ene the elimination of both chlorine atoms occurs affording a mixture of allene and methylacetylene. The reasons of the dual elimination reaction paths are considered.
- Levanova,Vakhrina,Grabel'Nykh,Rozentsveig,Russavskaya,Albanov,Korchevin
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p. 175 - 178
(2014/04/17)
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- Ceria in hydrogenation catalysis: High selectivity in the conversion of alkynes to olefins
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Active and selective: Ceria shows a high activity and selectivity in the gas-phase hydrogenation of alkynes to olefins (see picture). This unprecedented behavior has direct impact on the purification of olefin streams and, more importantly, it opens new perspectives for exploring this fascinating oxide as a catalyst for the selective hydrogenation of other functional groups.
- Vilé, Gianvito,Bridier, Blaise,Wichert, Jonas,Pérez-Ramírez, Javier
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experimental part
p. 8620 - 8623
(2012/10/08)
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- Palladium-catalyzed annulation reactions for diastereoselective cyclopentene synthesis
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Palladium-catalyzed annulation reactions of conjugate acceptors and allenyl boronic ester provide substituted cyclopentenes in high yields and, where applicable, diastereoselectivities. This method provides rapid assembly of building blocks for natural product synthesis, including polycyclic lactone and lactam products. Reactions are hypothesized to initiate by conjugate addition of a nucleophilic propargylpalladium complex.
- Kohn, Benjamin L.,Jarvo, Elizabeth R.
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supporting information; experimental part
p. 4858 - 4861
(2011/11/06)
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- UV laser photodeposition of nanomagnetic soot from gaseous benzene and acetonitrile-benzene mixture
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Megawatt KrF laser gas-phase photolysis of benzene and acetonitrile-benzene mixture was studied by using mass spectroscopy-gas-chromatography and Fourier transform infrared spectroscopy for analyses of volatile products, and by Fourier transform infrared, Raman and X-ray photoelectron spectroscopy, electron microscopy and magnetization measurements for analyses of solid products deposited from the gas-phase. The results are consistent with carbonization of benzene and decomposition of non-absorbing acetonitrile in carbonizing benzene through collisions with excited benzene and/or its fragments. The solid products from benzene and acetonitrile-benzene mixture have large surface area and are characterized as nanomagnetic amorphous carbonaceous soot containing unsaturated C centers prone to oxidation. The nanosoot from acetonitrile-benzene mixture incorporates CN groups, confirms reactions of benzene fragments with CN radical and has a potential for modification by reactions at the CN bonds.
- Pola, Josef,Ouchi, Akihiko,Mary?ko,Vorlí?ek,?ubrt, Jan,Bakardjieva,Bastl, Zdeněk
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experimental part
p. 188 - 194
(2012/02/02)
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- Study of the catalytic dehydrochlorination of 1,2-dichloropropane
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Catalytic dehydrochlorination of 1,2-dichloropropane in the presence of γ-Al2O3, CaX, and haydite was studied. A relationship between the catalytic activity and acidity of the catalysts under study was revealed.
- Nadzhafov, Dzh Yu
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scheme or table
p. 1532 - 1540
(2012/01/14)
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- Serendipity strikes again - Efficient preparation of lithium tetramethylcuprate(III) via rapid injection NMR
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Lithium tetramethylcuprate(iii), Me4CuLi, the CuIII analog of the Gilman reagent, has been prepared in high yield from halo-Gilman reagents Me2CuLi·LiX (X = Cl, Br, I) and 2,3-dichloropropene and found to have surprising thermal stability. The cyano-Gilman reagent (X = CN) follows a different pathway.
- Bartholomew, Erika R.,Bertz, Steven H.,Cope, Stephen K.,Murphy, Michael D.,Ogle, Craig A.,Thomas, Andy A.
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scheme or table
p. 1253 - 1254
(2010/07/05)
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- Photoisomerization and photochemistry of matrix-isolated 3-furaldehyde
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3-Furaldehyde (3FA) was isolated in an argon matrix at 12 K and studied using FTIR spectroscopy and quantum chemistry. The molecule has two conformers, with trans and cis orientation of the O=C-C=C dihedral angle. At the B3LYP/6-311++G(d,p) level of theory, the trans form was computed to be ca. 4 kJ mol-1 more stable than the cis form. The relative stability of the two conformers was explained using the natural bond orbital (NBO) method. In fair agreement with their calculated relative energies and the high barrier of rotamerization (ca. 34 kJ mol-1 from trans to cis), the trans and cis conformers were trapped in an argon matrix from the compound room temperature gas phase in proportion ～7:1. The experimentally observed vibrational signatures of the two forms are in a good agreement with the theoretically calculated spectra. Broad-band UV-irradiation (λ > 234 nm) of the matrix-isolated compound resulted in partial trans → cis isomerization, which ended at a photostationary state with the trans/cis ratio being ca. 1.85:1. This result was interpreted based on results of time-dependent DFT calculations. Irradiation at higher energies (λ > 200 nm) led to decarbonylation of the compound, yielding furan, cyclopropene-3-carbaldehyde, and two C3H4 isomers: cyclopropene and propadiene.
- Kus, Nihal,Reva, Igor,Fausto, Rui
-
scheme or table
p. 12427 - 12436
(2011/02/28)
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- Rate constants and the H atom branching ratio of the reactions of the methylidyne CH(X2Π) radical with C2H2, C2H4, C3H4 (methylacetylene and allene), C3H6 (
-
The reactions of the CH radical with several unsaturated hydrocarbons C2H2 (acetylene), C2H4 (ethylene), C3H4 (methyl-acetylene and allene), C3H 6 (propene) and C
- Loison, Jean-Christophe,Bergeat, Astrid
-
scheme or table
p. 655 - 664
(2009/05/07)
-
- Cyclic versus linear isomers produced by reaction of the methylidyne radical (CH) with small unsaturated hydrocarbons
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The reactions of the methylidyne radical (CH) with ethylene, acetylene, allene, and methylacety- lene are studied at room temperature using tunable vacuum ultraviolet (VUV) photoionization and time- resolved mass spectrometry. The CH radicals are prepared by 248 nm multiphoton photolysisof CHBr 3 at 298 K and react with the selected hydrocarbon i n a helium gas flow. Analysis of photoionization efficiency versus VUV photon wavelength permits isomer-specific detection of the reaction products and allows estimation of the reaction product branching ratios. The reactions proceed by either CH insertion or addition followed by H atom elimination from the intermediate adduct. In the CH + C 2 H 4 reaction the C 3 H 5 intermediate decays byH atom loss to yield 70(±8)percent allene, 30(±8)percent methylacetylene, and less than 10percent cyclopropene, in agreement with previous RRKM results. In the CH + acetylene reaction, detection of mai nly the cyclic C 3 H 2 isomer is contrary to a previous RRKM calculations that predicted linear triplet propargylene to be 90percent of the total H-atom coproducts. High-level CBS-APNO quantum calculations and RRKM calculations for the CH + C 2 H 2 reaction presented in this manuscript predict a higher contribution of the cyclic C 3 H 2 (27.0percent) versus triplet propargylene (63.5percent) than earlier predictions. Extensive calculations onthe C 3 H 3 and C 3 H 2 D system combined with experimental isotope ratios for the CD + C 2 H2 reaction indicate that H-atom-assisted isomerization in the present experiments is responsible for the remaining discrepancy between the new RRKM calculations and the experimental results. Cyclic isomers are also found to represent 30(±6)percent of the detected products in the case of CH + methylacetylene, together with 33(±6)percent 1,2,3- butatriene and 37(±6)percent vinylacetylene. The CH + allene reaction gives 23(±5)percent 1,2,3-butatriene and 77(±5)percent vinylacetylene, whereas cyclic isomers are produced below the detection limit in this reaction. The reaction exit channels deduced by comparing the product distributions for the aforementioned reactions are discussed in detail.
- Goulay, Fabien,Trevitt, Adam J.,Meloni, Giovanni,Selby, Talitha M.,Osborn, David L.,et al.
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experimental part
p. 993 - 1005
(2009/06/28)
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- Detailed chemical kinetic modeling of pyrolysis of ethylene, acetylene, and propylene at 1073-1373 K with a plug-flow reactor model
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This study examines the predictive capability of our recently proposed reaction mechanism (Norinaga and Deutschmann, Ind Eng Chem Res 2007, 46, 3547) for hydrocarbon pyrolysis at varying temperature. The conventional flow reactor experiments were conducted at 8 kPa, over the temperature range 1073-1373 K, using ethylene, acetylene, and propylene as reactants to validate the mechanism. More than 40 compounds were identified and quantitatively analyzed by on- and off-line gas chromatography. The chemical reaction schemes consisting of 227 species and 827 reactions were coupled with a plug-flow reactor model that incorporated the experimentally measured axial temperature profile of the reactor. Comparisons between the computations and the experiments are presented for more than 30 products including hydrogen and hydrocarbons ranging from methane to coronene as a function of temperature. The model can predict the compositions of major products (mole fractions larger than 10-2) in the pyrolysis of three hydrocarbons with satisfactory accuracies over the whole temperature range considered. Mole fraction profiles of minor compounds including polycyclic aromatic hydrocarbons (PAHs) up to three ring systems, such as phenanthrene, anthracene, and phenylnaphthalene, are also fairly modeled. At temperatures lower than 1273 K, larger PAHs were underpredicted and the deviation became larger with decreasing temperature and increasing molecular mass of PAHs, while better agreements were found at temperatures higher than 1323 K.
- Norinaga, Koyo,Janardhanan, Vinod M.,Deutschmann, Olaf
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p. 199 - 208
(2008/09/18)
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- Azo-coupling and reduction of cyclopropanediazonium ions in the reactions with polyhydroxyarenes and aminophenols
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A reaction of cyclopropanediazonium ion, generated by decomposition of N-cyclopropyl-N-nitrosourea upon treatment with potassium or cesium carbonates, with various poly-hydroxyarenes and aminophenols has been studied. The reaction of azo-coupling proceeds with phloroglucinol, resorcinol, 3-methoxy- and 3-aminophenol giving rise to mono-, bis-, and tris(cyclopropylazo)arenes as the major products. Oxidizable phenols such as hydro-quinone, 2-methoxy-, 4-amino-, and 2-aminophenol give products of radical transformations with participation of cyclopropyl radical.
- Shulishov,Klimenko,Korolev,Kostyuchenko,Okonnishnikova,Tomilov
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experimental part
p. 1703 - 1711
(2011/04/23)
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- Theoretical and experimental studies of the diketene system: Product branching decomposition rate constants and energetics of isomers
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The kinetics and mechanism for the thermal decomposition of diketene have been studied in the temperature range 510-603 K using highly diluted mixtures with Ar as a diluent. The concentrations of diketene, ketene, and CO2 were measured by FTIR spectrometry using calibrated standard mixtures. Two reaction channels were identified. The rate constants for the formation of ketene (k1) and CO2 (k2) have been determined and compared with the values predicted by the Rice-Ramsperger-Kassel-Marcus (RRKM) theory for the branching reaction. The first-order rate constants, k 1 (s-1)= 1015.74±0.72 exp(-49.29 (kcal mol-1) (±1.84)/RT) and k2 (s-1)= 10 14.65±0.87 exp(-49.01 (kcal mol-1) (±2.22)/RT); the bulk of experimental data agree well with predicted results. The heats of formation of ketene, diketene, cyciobuta-1,3dione, and cyclobuta-1,2-dione at 298 K computed from the G2M scheme are -11.1, -45.3, -43,6, and -40,3 kcal mol-1, respectively.
- Bui, Binh,Tsay, Ti Jo,Lin,Melius
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p. 580 - 590
(2008/09/18)
-
- Membrane reactor process for chemical conversions
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Processes for chemical conversion of volatile organic compounds to value added products using multiphasic membrane reactors are described. More particularly the multiphasic materials comprising two or more phases bound to one another which in the form of a solid state membrane demonstrate an ability to selectively convey electrons, hydrogen and oxygen between different gaseous mixtures. Characteristics of such multiphasic materials provide independent, controllable, counter-current transport of hydrogen, electrons and oxygen.
- -
-
Page/Page column 9-10
(2008/06/13)
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- Polyolefin processes with constituent high conversion alkane dehydrogenation in membrane reactors
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Polymerization processes having as constituent parts high conversion membrane reactors, that provide a source of monomer, and subsequent polymerization of the monomer, without passing products of the conversion through an alkane/alkene splitter, are disclosed. Polymers of light alkene hydrocarbons, such as ethylene, propylene and alkenes consisting of up to 6 carbon atoms, are prepared from gaseous feedstreams consisting predominantly of volatile alkane compounds substantially free of dihydrogen and/or dioxygen. Equipment required for separation of alkene products from unreacted alkanes in conventional plants is eliminated because of the high alkane conversions provided in the membrane reactors. Particularly useful are flow reactors comprising dense membranes of multiphasic materials that provide independent, controllable, counter-current transport of hydrogen, electrons and oxygen.
- -
-
Page/Page column 8
(2008/06/13)
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- Ni catalyst, process for making catalysts and selective hydrogenation process
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More selective and efficient Ni hydrotreating catalysts are those which contain more than about 60% of the Ni content on the peripheral surface of porous supports, such as extruded alumina, which may be obtained by spraying an atomized solution of a Ni compound onto the support and drying it at a temperature in the range of from 200 to 600° C. When used, for example, to remove acetylenic compounds from butadiene streams, higher recovery of the desired butadiene with lower acetylenic content and low heavy polymer deposition is obtained than was possible with prior catalysts.
- -
-
Page/Page column 2
(2010/02/14)
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- Stereocontrolled syntheses of the nemorensic acids using 6-diazoheptane-2,5-dione in carbonyl ylide cycloadditions
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Levulinic acid-derived 6-diazoheptane-2,5-dione (9) serves as a common precursor in a formal synthesis of frontalin 19, and in syntheses of cis-nemorensic acid 1, 4-hydroxy-cis-nemorensic acid 2, 3-hydroxy-cis-nemorensic acid 3, and nemorensic acid 4. The key step in these syntheses is the Rh 2(OAc)4-catalyzed tandem carbonyl ylide formation-intermolecular 1,3-dipolar cycloadditions of diazodione 9 with formaldehyde, alkynes or allene, which occur with high regioselectivity. Subsequent oxidative cleavage of the ring originally derived from the cyclic carbonyl ylide intermediate provides a straightforward access to polysubstituted tetrahydrofurans, and in particular an efficient entry to the nemorensic acids. Enantioselective cycloadditions with diazodione 9, using chiral rhodium catalysts, gave cycloadducts in up to 51% ee.
- Hodgson, David M.,Le Strat, Frederic,Avery, Thomas D.,Donohue, Andrew C.,Brueckl, Tobias
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p. 8796 - 8803
(2007/10/03)
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- The thermal decomposition of 5-membered rings: A laser pyrolysis study
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The mechanisms of pyrolysis of cyclopentadiene, furan, pyrrole and thiophene have been investigated using a combination of IR laser powered homogeneous pyrolysis, chemical and physical trapping of radical intermediates, and use of precursors specifically designed to generate selected radical intermediates. The results confirm the central role played by free radicals in the cases of cyclopentadiene and thiophene, and the dominant step of 1,2-H shifts in the cases of furan and pyrrole. The experimental results may be interpreted according to the high level ab initio calculations recently reported in the literature.
- Hore, Nathan R.,Russell, Douglas K.
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p. 606 - 613
(2007/10/03)
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- Production of olefins
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A process for the catalytic cracking of an olefin-containing feedstock which is selective towards light olefins in the effluent, the process comprising contacting a hydrocarbon feedstock containing at least one olefin with a MFI-type crystalline silicate catalyst having a silicon/aluminum atomic ratio of at least about 180, which has been obtained by pretreating so as to increase the silicon/aluminum atomic ratio thereof by heating the catalyst in steam and de-aluminating the catalyst by treating the catalyst with a complexing agent for aluminum, at an inlet temperature of from 500 to 600° C. and at an olefin partial pressure of from 0.1 to 2 bars to produce an effluent with an olefin content of lower molecular weight than that of the feedstock.
- -
-
Page/Page column 14-15
(2008/06/13)
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- Crossed beam investigations of the reaction dynamics of O(3P) with allyl radical, C3H5
-
The nascent rovibrational distributions of the OH product from the newly observed exothermic reaction of O(3P)+C3H5→ C3H4+OH were studied. The atom-radical reaction dynamics was first probed through t
- Kwon, Han-Cheol,Park, Jong-Ho,Lee, Hohjai,Kim, Hee-Kyung,Choi, Young-Sang,Choi, Jong-Ho
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p. 2675 - 2679
(2007/10/03)
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- Laser powered homogeneous pyrolysis of ethyne, propyne, and propadiene initiated by methyl radicals: Formation and degradation of hydrocarbons at 800-950 K
-
Applying laser heating by fast vibrational-translational energy transfer in a quasi-wall-free reactor the pyrolysis of ethyne (C2H2), propyne (p-C3H4), and propadiene (a-C3H4) was studied experimentally at 0.13 bar in the medium temperature range of 800-950 K with respect to the degradation and formation of hydrocarbons. The radical/hydrocarbon chemistry was chemically induced via CH3 radicals produced by the fast thermal dissociation of di-tert-butyl-peroxide DTBP ((tert-C4H9O)2 → 2 CH3 + 2 CH3COCH3). Complete analysis of the product yields was achieved by means of GC-MS with special attention to isomeric product and benzene formation. The product distribution, the temperature dependence and the underlying reaction schemes were analyzed by kinetic models developed for high temperature alkane oxidation/pyrolysis and aromatic formation in premixed ethene and ethyne flames. The primary attack of the unsaturated hydrocarbons by CH3 radicals in the studied temperature range occurs via the addition to the double/triple bond and via hydrogen atom abstraction, leading to different classes of radicals. For the reaction system C2H2 + CH3 high yields of C6H6 with a marked negative temperature dependence were observed. A semi-quantitative description of the C6H6 yield was obtained by a reaction sequence of successive addition of C2H2 to the radicals C2H3 (from C2H2 + H) and C4H5, being consistent with recent discussed reaction networks. For the reaction systems p-C3H4 + CH3 and a-C3H4 + CH3 only qualitative agreement between measured and modelled product yields was found, pointing to a lack of reliable data of the reactions of p-C3H4/a-C3H4/C3H 3/H. Modified mechanisms are presented for the radical rich reaction systems C2H2 + CH3, p-C3H4 + CH3, and a-C3H4 + CH3 experimentally studied.
- Goos, Elke,Hippler, Horst,Hoyermann, Karlheinz,Juerges, Bettina
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p. 2011 - 2018
(2007/10/03)
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- Electrosynthesis of Allene (propadiene) and of propyne (methylacetylene) through the anodic decarboxylation reaction (part 2)
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The anodic decarboxylation reaction is a general reaction that can be applied with success to several suitable precursors. This work presents the electrochemical synthesis of allene by anodic oxidation of potassium itaconate. It is also shown that the anodic oxidation of potassium citraconate produces propyne. In both cases, unsaturated hydrocarbons were formed together with CO and CO2. The electrooxidation of potassium crotonate leads to a simultaneous formation of propyne and allene (the latter in considerably smaller amounts than the former). Also in this case, formation of the unsaturated hydrocarbons is accompanied by the formation of CO and CO2.
- Cataldo, Franco
-
-
- Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
-
Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
- Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
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p. 402 - 415
(2007/10/03)
-
- Spin chemistry of organometallic compounds: Part 1. Interaction of N-bromohexamethyldisilazane with allyltriethylstannane
-
It has been shown, on the basis of the analysis of CIDNP effects, that allene and (Me3Si)2NH - major products of the photoinduced reaction of Et3SnCH2CH=CH2 and (Me3Si)2NBr - result from a radical pair comprised of ·CH2CHBrCH2SnEt3 and ·N(SiMe3)2 free radicals. Allene is formed through the β-cleavage of the short-lived homolytic substitution product Et3SnCH2CBr=CH2.
- Taraban, Marc B.,Kruppa, Alexander I.,Rakhlin, Vladimir I.,Grigor'Ev, Stanislav I.,Volkova, Olga S.,Mirskov, Rudolph G.,Leshina, Tatyana V.
-
-
- Palladium catalysed tandem cyclisation-anion capture. Part 8: Cascade hydrostannylation-cyclisation-anion capture and cascade hydroboration-cyclisation-anion capture on solid phase
-
Up to four bonds and five stereocentres are created, in five component processes (five point diversity), utilising resin bound aryl iodides by hydroboration or hydrostannylation of alkynes, followed by cyclisation-anion capture involving Suzuki or Stille reactions. Three small libraries were prepared to validate the chemistry.
- Grigg, Ronald,MacLachlan, William S,MacPherson, David T,Sridharan, Visuvanathar,Suganthan, Selvaratnam
-
p. 10335 - 10345
(2007/10/03)
-
- The gas-phase pyrolysis of nitrocyclobutanes: A shock-tube investigation supplemented with DFT calculations of their thermochemical and structural parameters
-
Mono- and 1,1-dinitrocyclobutanes (highly diluted in Ar) were pyrolyzed at temperatures 860-1300 K in reflected shocks. Activation energies for their initial fragmentations were derived from measurements of relative rates of species loss, compared to cyclobutyl chloride and isopropyl bromide: kuni(NCB) = 9.66 × 1012 exp(-25264/T), s-1, kuni(DNCB) = 6.26 × 1012exp(-21 087/T),s-1 The production and decay of NO2 was monitored in real time via its absorption at 405 nm. The identity and amounts of the species produced during 1.3ms residence time were determined by FTIR and GC analysis of samples extracted from the tube terminus, after being quenched by an expansion wave. Plausible mechanisms that account for the observed product distributions are proposed. In a computational Appendix, the results of density functional theory (DFT) calculations are presented for enthalpies and entropies of several mono-substituted cyclobutanes and for 1,1-dinitrocyclobutane, as well as for selected fragmentation products. by Oldenbourg Wissenschaftsverlag, Muenchen.
- Zhang, Yi-Xue,Wilcox,Bauer
-
p. 1165 - 1192
(2007/10/03)
-
- Ion chemistry in XH4/allene (X = Ge, Si) gaseous mixtures - Formation of X-C bonds
-
The gas-phase ion chemistry of germane/allene and silane/allene mixtures has been studied, with the aim of obtaining information on the experimental conditions leading to the formation of clusters of increasing size containing Ge or Si bonded to carbon atoms. Mechanisms of ion/molecule reactions have been elucidated by ion-trap mass spectrometry using single and multiple isolation steps. Rate constants for the most important reactions have been determined experimentally and compared with collisional rate constants. The germane/allene mixtures display a low reactivity and the most abundant germanium and carbon containing ion is GeCH3/+. However, chain propagation proceeds after the first nucleation step, even if rather slowly, with the formation of large clusters such as Ge4C3H3/+ at low abundance. In contrast, the silane/allene mixtures are very reactive and many different processes are observed, with the formation of several silicon and carbon containing ions with appreciable efficiency. Chain propagation proceeds mainly through reactions of silicon-containing ions with allene molecules and the subsequent formation of large clusters such as Si3C3H5/+ and Si4C3H7/+.
- Benzi, Paola,Operti, Lorenza,Rabezzana, Roberto
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p. 505 - 512
(2007/10/03)
-
- Flash vacuum pyrolysis and photolysis of 3,3,5,5-tetramethylpyrazolin-4- one - A matrix isolation study
-
The flash vacuum pyrolysis of 3,3,5,5-tetramethylpyrazolin-4-one (4) with subsequent trapping of the products in argon at 10 K results in the formation of a complex product mixture with tetramethylcyclopropanone (5) as one of the minor constituents. The 193 nm photochemistry of matrix-isolated 4 is much cleaner, yielding cyclopropanone 5 and allene oxide 9 as the major products. The reaction of tetramethylallene 13 with oxygen atoms yields the same product mixture of 5 and 9 and thus provides an independent route to these species. The experimental IR spectra of 5 and 9 are in good agreement with the results from DFT calculations.
- Sander, Wolfram,Wrobel, Roman,Komnick, Peter,Rademacher, Paul,Muchall, Heidi M.,Quast, Helmut
-
-
- Solid xenon: A medium for unusual photoreactions
-
Can propane be fragmented photolytically with light of wavelength greater than 170 nm [Eq. (1)]? One might think: No! By photolysis in a xenon matrix, in fact, three variants are available to reach this goal.
- Maier, Guenther,Lautz, Christian
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p. 2038 - 2041
(2007/10/03)
-
- A novel acid stable/base labile carbamate linker for N-acyliminium ion reactions on solid support
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The development of a novel carbamate linker optimized for solid phase N- acyliminium ion chemistry is reported. Some 2- and 2,4-substituted pyrrolidines were synthesized via addition of several carbon nucleophiles to immobilized N-acyliminium ions. A β-sulfonylethyl carbamate linker appeared especially useful; readily synthesized, stable towards Lewis acids and easily cleavable.
- Veerman, Johan J. N.,Rutjes, Floris P. J. T.,Van Maarseveen, Jan H.,Hiemstra, Henk
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p. 6079 - 6082
(2007/10/03)
-
