563-79-1Relevant articles and documents
Kinetics of the thermal isomerization of 1,1,2-trimethylcyclopropane
Lewis, David K.,Hughes, Steven V.,Miller, Justine D.,Schlier, Jessica,Wilkinson, Kevin A.,Wilkinson, Sara R.,Kalra, Bansi L.
, p. 475 - 482 (2006)
The Arrhenius parameters for the gas phase, unimolecular structural isomerizations of 1,1,2-trimethylcyclopropane to three isomeric methylpentenes and two dimethyl-butenes have been determined over a wide range of temperatures, 688-1124 K, using both static and shock tube reactors. For the overall loss of reactant. Ea =63.7 (±0.5) kcal/mol and log10 A= 15.28 (±0.12). These values are higher by 2.6 kcal/mol and 0.7-0.8 than previously reported from experimental work or predicted from thermochemical calculations. Ea for the formation of trans-4-methyl-2-pentene is 1.5 kcal/mol higher than Ea for the formation of the cis isomer, which is identical to the Ea difference previously reported for the formation of trans- and cis-2-butene from methylcyclopropane. Substitution of methyl groups for hydrogen atoms on the cyclopropane ring is expected to weaken the C - C ring bonds, and it has been reported previously that activation energies for structural isomerizations of methylcyclo-propanes do decrease substantially over the series cyclopropane > methylcyclopropane > 1, 1-or 1,2-dimethylcyclopropane. However, the present study shows that the trend does not continue beyond dimethylcyclopropane isomerization. Besides reductions in C - C bond energy, steric interactions may be increasingly important in determining the energy surface and conformational restrictions near the transition state in isomerizations of the more highly substituted methylcyclopropanes.
Rodgers,Wu
, p. 6913,6914, 6915, 6916 (1973)
Cyclopentadienyl(allyl) (butadiene)hafnium compounds. Synthesis, crystal structure, and dynamics of cyclopentadienyl(1,2,3-trimethylallyl)(1,2-dimethylbutadiene)-hafnium and cyclopentadienyl(1,1,2-trimethylallyl)-(2,3-dimethylbutadiene)hafnium
Prins, Thomas J.,Hauger, Bryan E.,Vance, Peter J.,Wemple, Michael E.,Kort, David A.,O'Brien, Jonathan P.,Silver, Michael E.,Huffman, John C.
, p. 979 - 985 (1991)
The reaction of CpHfCl3·2THF with 2 equiv of (1,2,3-Me3allyl)MgBr or (1,1,2-Me3allyl)MgBr yields Cp(1,2,3-Me3allyl)(1,2-Me2butadiene)Hf (3) or Cp(1,1,2-Me3allyl)(2,3-Me2butadiene)Hf (4). X-ray crystallography of 3 shows that both the allyl and butadiene ligands assume a prone orientation with respect to Cp. For 3: cell constants a = 15.109 (5), b = 7.150 (2), c = 15.587 (6) A?, β = 115.41 (1)°; space group P21/c; R = 0.0305, Rw = 0.0347. Variable-temperature 1H NMR studies indicate that compound 3 is static on the NMR time scale whereas 4 exists in two isomeric forms and undergoes three separate dynamic processes involving η3-η1 isomerization at the unsubstituted and substituted ends of the allyl ligand [ΔG? = 39.4 ± 1.0 kJ/mol and 73.4 ± 1.0 kJ/mol, respectively] and butadiene flip [ΔG?(avg) = 49.8 ± 1.0 kJ/mol].
Pulse Radiolysis and E.S.R. Evidence for the Formation of an Alkene Radical Cation in Aqueous Solution
Asmus, Klaus-Dieter,Williams, Peter S.,Gilbert, Bruce C.,Winter, Jeremy N.
, p. 208 - 210 (1987)
Direct pulse radiolysis evidence, complemented by e.s.r. experiments, establishes that the radical cation Me2C=-C.Me2 (λmax ca. 290 nm) is formed by acid-catalysed elimination of OH- from .CMe2CMe2OH; the radica
Turro et al.
, p. 955 (1964)
Radiolytic Generation of Organic Radical Cations in Zeolite Na-Y
Qin, X.-Z.,Trifunac, A. D.
, p. 4751 - 4754 (1990)
Several examples of radiolytically generated organic radical cations in zeolite Na-Y are illustrated.EPR studies of organic radical cations can be carried out in a wide range of temperatures up to room temperature.In every case, monomeric radical cations were observed.Comparison to previous work in freon and xenon matrices is made, illustrating that in the zeolite Na-Y there is considerably weaker radical cation-host interaction.A mechanism of radiolytic generation of radical cations in zeolite Na-Y is proposed.
Highly Active Superbulky Alkaline Earth Metal Amide Catalysts for Hydrogenation of Challenging Alkenes and Aromatic Rings
Eyselein, Jonathan,F?rber, Christian,Grams, Samuel,Harder, Sjoerd,Knüpfer, Christian,Langer, Jens,Martin, Johannes,Thum, Katharina,Wiesinger, Michael
supporting information, p. 9102 - 9112 (2020/03/30)
Two series of bulky alkaline earth (Ae) metal amide complexes have been prepared: Ae[N(TRIP)2]2 (1-Ae) and Ae[N(TRIP)(DIPP)]2 (2-Ae) (Ae=Mg, Ca, Sr, Ba; TRIP=SiiPr3, DIPP=2,6-diisopropylphenyl). While monomeric 1-Ca was already known, the new complexes have been structurally characterized. Monomers 1-Ae are highly linear while the monomers 2-Ae are slightly bent. The bulkier amide complexes 1-Ae are by far the most active catalysts in alkene hydrogenation with activities increasing from Mg to Ba. Catalyst 1-Ba can reduce internal alkenes like cyclohexene or 3-hexene and highly challenging substrates like 1-Me-cyclohexene or tetraphenylethylene. It is also active in arene hydrogenation reducing anthracene and naphthalene (even when substituted with an alkyl) as well as biphenyl. Benzene could be reduced to cyclohexane but full conversion was not reached. The first step in catalytic hydrogenation is formation of an (amide)AeH species, which can form larger aggregates. Increasing the bulk of the amide ligand decreases aggregate size but it is unclear what the true catalyst(s) is (are). DFT calculations suggest that amide bulk also has a noticeable influence on the thermodynamics for formation of the (amide)AeH species. Complex 1-Ba is currently the most powerful Ae metal hydrogenation catalyst. Due to tremendously increased activities in comparison to those of previously reported catalysts, the substrate scope in hydrogenation catalysis could be extended to challenging multi-substituted unactivated alkenes and even to arenes among which benzene.
A smarter approach to catalysts by design: Combining surface organometallic chemistry on oxide and metal gives selective catalysts for dehydrogenation of 2,3-dimethylbutane
Rouge, Pascal,Garron, Anthony,Norsic, Sébastien,Larabi, Cherif,Merle, Nicolas,Delevoye, Laurent,Gauvin, Regis M.,Szeto, Kai C.,Taoufik, Mostafa
, p. 21 - 26 (2019/04/25)
2,3-dimethylbutane is selectively converted into 2,3-dimethylbutenes at 500 °C under hydrogen or at 390 °C under nitrogen in the presence of bimetallic catalysts Pt-Sn/Li-Al2O3. The high stability of the catalyst along the reaction is obtained by selective modification of the Pt/Li-Al2O3 catalyst using Surface Organometallic Chemistry (SOMC).