6755-54-0Relevant academic research and scientific papers
Reaction Mechanism and Kinetics of Olefin Metathesis by Supported ReOx/Al2O3 Catalysts
Lwin, Soe,Wachs, Israel E.
, p. 272 - 278 (2016/01/12)
The self-metathesis of propylene by heterogeneous supported ReOx/Al2O3 catalysts was investigated with in situ Raman spectroscopy, isotopic switch (D-C3= → H-C3=), temperature-programmed surface reaction (TPSR) spectroscopy, and steady-state kinetic studies. The in situ Raman studies showed that two distinct surface ReO4 sites are present on alumina and that the olefins preferentially interact with surface ReO4 sites anchored at acidic surface sites of alumina (olefin adsorption: C4= > C3= > C2=). The isotopic switch experiments demonstrate that surface Re?CH3 and Re?CHCH3 are present during propylene metathesis, with Re? representing activated surface rhenia sites. At low temperatures (3=][Re?]2. At high temperatures (>100 °C), the rate-determining step is the recombination of two surface propylene molecules (rate ≈ [C3=]2[Re?]). To a lesser extent, the recombination of surface Re?CH3 and Re?CHCH3 intermediates also contributes to self-metathesis of propylene at elevated reaction temperatures.
Metal ions do not play a direct role in the formation of carbon-carbon triple bonds during reduction of trihaloalkyls by CrII or V II
Levy, Ophir,Bino, Avi
supporting information, p. 15944 - 15947 (2013/02/23)
Carbyne radicals: Reactions of trihaloalkyl compounds with Cr2+ or V2+ in aqueous solutions yield alkynes and other products. Stepwise halogen abstractions from the trihaloalkyls form alkyl carbyne triradicals in solution. These radicals undergo coupling reactions, producing triply bonded alkyne molecules (see scheme). This process is not metal-assisted and does not occur in the coordination sphere of the metal ions.
Efficient functionalisation of cubic monovinylsilsesquioxanes via cross-metathesis and silylative coupling with olefins in the presence of ruthenium complexes
Zak, Patrycja,Pietraszuk, Cezary,Marciniec, Bogdan,Spolnik, Brzegorz,Danikiewicz, Witold
body text, p. 2675 - 2682 (2010/04/05)
Monovinylheptaisobutylsilsesquioxane undergoes efficient cross-metathesis and silylative coupling with styrenes. Allyl derivatives were successfully tested in cross-metathesis in the presence of first generation Grubbs' catalyst, while heteroatom-substitu
Coupling reactions in aldehydes adsorbed on V(100) single-crystal surfaces
Shen, Min,Zaera, Francisco
experimental part, p. 8708 - 8713 (2009/10/23)
The thermal chemistry of formaldehyde on vanadium (100) single-crystal surfaces was characterized under ultrahigh vacuum (UHV) conditions by using temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) in combination with isotope-labeling experiments. Particular emphasis was placed on establishing a mechanism for the formation of ethylene, which was observed to desorb in two temperature regimes, at 290 and 540 K. The low-temperature reaction was determined to occur via the coupling of methylene groups formed on the surface upon dissociation of the C-O bond in adsorbed formaldehyde. The high-temperature ethylene, on the other hand, was proven to require the prior formation of a diolate, -OCH2CH2O-, intermediate. This chemistry was shown to be quite general, also occuring in cross-coupling mode between two different coadsorbed aldehydes.
The Yukawa-Tsuno relationship for the β-silicon effect in the solvolysis rates of 2-(aryldimethylsilyl)ethyl chlorides
Fujio, Mizue,Uchida, Mai,Okada, Ayumi,Alam, Md. Ashadul,Fujiyama, Ryoji,Siehl, Hans-Ullrich,Tsuno, Yuho
, p. 1834 - 1842 (2007/10/03)
Solvolysis rates of 2-(aryldimethylsilyl)ethyl chlorides were determined conductimetrically in 60% (v/v) aqueous ethanol. The effects of aryl substituents at the silyl atom on the solvolysis rates at 50°C were correlated with essentially nonresonant σ parameters of r = 0:10 in terms of Yukawa-Tsuno (Y-T) Eq. 1, giving a ρ value of -1:75. Such a high ρ value may be regarded as the effect of aryl ring on the bridged Si in the rate-determining step. The Si-bridging is consistent with the fact that the solvolysis of the unsubstituted substrate with d2-labeled ethylene moiety gave substitution products with label scrambling. The arylsilyl substituent effects were likewise analyzed for several relevant sets of β-silyl systems in order to ascertain significant variations of ρ values from system to system; Y-T Eq. 1 correlated quite excellently with essentially nonresonant sigmas of negligible resonance demand (r ? 0:10), to exhibit significant variations of ρ from -1:75 to -0:95.
The effect of substituents at silicon on the cross-metathesis of trisubstituted vinylsilanes with olefins
Pietraszuk, Cezary,Fischer, Helmut,Rogalski, Szymon,Marciniec, Bogdan
, p. 5912 - 5921 (2007/10/03)
Efficient cross-metathesis of vinylsilanes, carrying a large spectrum of different substituents at silicon, with various olefins in the presence of the first and second generation Grubbs catalyst and Hoveyda-Grubbs catalyst is described. On the basis of the results of equimolar reactions of vinylsilanes with ruthenium alkylidene complexes and experiments with deuterium-labelled reagents, a general, metallacarbene mechanism for the cross-metathesis of trisubstituted vinylsilanes with olefins has been suggested. Reaction was proved to be a valuable method for synthesis of unsaturated organosilicon derivatives.
Matrix Isolation Investigation of the Room Temperature and Pyrolytic Reactions of (CH3)2Zn with CH3OH and CH3SH
Bai, Hebi,Ault, Bruce S.
, p. 10492 - 10497 (2007/10/02)
Matrix isolation and cryogenic thin film approaches have been employed for the synthesis, isolation, and characterization of 1:1 and 1:2 complexes of (CH3)2Zn with CH3OH and CH3SH.These complexes were characterized by a shifting of certain sensitive vibrational modes of the acid and base subunits in the complex.The ratio of the 1:1 and 1:2 complexes could be altered by changing the relative amounts of the two reagents employed in a given experiment or by warming the cryogenic thin film from 14 K to as high as 200 K.Merged jet mixtures of (CH3)2Zn with either CH3OH and its isotopomers or CH3SH were also pyrolyzed at temperatures as high as 370 deg C.For the (CH3)2Zn/CH3OH pair, significant production of CH4 and CH2O was observed with minor amounts of C2H4.In the (CH3)2Zn/CH3SH experiments a substantial yield of (CH3)2S and CH4 was obtained.These pyrolytic reactions and products have not been reported previously and may have implications for the chemical vapor deposition of ZnO and ZnS.
Surface Far-Ultraviolet Photochemistry of Ethyl Chloride on GaAs(1000)
Liberman, Vladimir,Nooney, Matthew G.,Amata, Richard J.,Martin, Richard M.
, p. 2261 - 2269 (2007/10/02)
The photoinduced dissociation at 193 nm of monolayer ethyl chloride (EtCl) was studied on the Ga-rich GaAs(100) (8x2)Ga surface at 90 K.Photodepletion of EtCl is efficient, with a cross section of 6 x 10-19 cm2.Sixty percent of the EtCl molecules depleted by irradiation give ethyl groups bonded to the surface.The ethyl groups are stable up to ca. 500 K, which is the onset of thermal desorption of the products.The thermal desorption products are C2H4, C2H5, C2H6, H2 and GaCl.The hydrocarbon product distribution is approximately 70percent C2H4, 20percent C2H6, and 10percent C2H5 radicals.Experiments with CD3CH2Cl provide evidence that ethylene is formed by β-hydride elimination.The zero-coverage first-order kinetic parameters for this reaction are approximately Ea = 100 kJ/mol and A = 4.4 x 107 s-1.Comparison with the gas-phase photodissociation cross section indicates that the photodepletion is primarily due to substrate-mediated processes rather than to direct photodissociation of EtCl.The most probable mechanism involves photogenerated electron transport to the surface followed by electron dissociative attachment to EtCl.
Laser-Powered Decomposition of Spiroalkanes (n = 2-5)
Fajgar, Radek,Pola, Josef
, p. 7709 - 7717 (2007/10/02)
The laser heating of spiroalkanes (n=2-5) and of their 1,1,2,2-tetradeuterated isotopomers reveals dissimilar modes of their thermal decomposition.Spiropentane decomposes into ethene and propadiene via two competing routes: the direct cleavage and the more important cleavage via intermediary methylenecyclobutane.Spirohexane decomposes through two important concurrent pathways which are the expulsions of ethene from the three-membered ring and a more feasible expulsion of ethene from the four-membered ring.Spiroheptane and spirooctane decompose by a radical-chain mechanism and afford complex mixtures of products; upon addition of propene both compounds rearrange into two cycloalkanes wherein the larger ring of the spiroalkane is preserved and substituted with ethylidene and a vinyl group.
The mechanism of the infrared laser induced multiphoton decomposition of ethyl alcohol
Goodale, J. W.,Evans, D. K.,Ivanco, M.,McAlpine, Robert D.
, p. 1437 - 1439 (2007/10/02)
The infrared laser induced multiphoton decomposition of ethyl alcohol has been studied in experiments with iodine as a radical scavenger and the deuterium substituted from CH3CD2OH of the alcohol.These experiments show that the principle product, C2H4, arises from a concerned molecular elimination, as do most of the CH4 and CH3CHO.The C2H6 product results from recombination of nascent methyl radicals formed in the minor bond breaking channel.
