- Synthesis of Supported Planar Iron Oxide Nanoparticles and Their Chemo- and Stereoselectivity for Hydrogenation of Alkynes
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Nature uses enzymes to dissociate and transfer H2 by combining Fe2+ and H+ acceptor/donor catalytic active sites. Following a biomimetic approach, it is reported here that very small planar Fe2,3+ oxide nanoparticles (2.0 ± 0.5 nm) supported on slightly acidic inorganic oxides (nanocrystalline TiO2, ZrO2, ZnO) act as bifunctional catalysts to dissociate and transfer H2 to alkynes chemo- and stereoselectively. This catalyst is synthesized by oxidative dispersion of Fe0 nanoparticles at the isoelectronic point of the support. The resulting Fe2+,3+ solid catalyzes not only, in batch, the semihydrogenation of different alkynes with good yields but also the removal of acetylene from ethylene streams with >99.9% conversion and selectivity. These efficient and robust non-noble-metal catalysts, alternative to existing industrial technologies based on Pd, constitute a step forward toward the design of fully sustainable and nontoxic selective hydrogenation solid catalysts.
- Tejeda-Serrano, María,Cabrero-Antonino, Jose R.,Mainar-Ruiz, Virginia,López-Haro, Miguel,Hernández-Garrido, Juan C.,Calvino, José J.,Leyva-Pérez, Antonio,Corma, Avelino
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p. 3721 - 3729
(2017/06/09)
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- Enzymatic Oxidative Tandem Decarboxylation of Dioic Acids to Terminal Dienes
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The biocatalytic oxidative tandem decarboxylation of C7–C18dicarboxylic acids to terminal C5–C16dienes was catalyzed by the P450 monooxygenase OleT with conversions up to 29 % for 1,11-dodecadiene (0.49 g L–1). The sequential nature of the cascade was proven by the fact that decarboxylation of intermediate C6–C11ω-alkenoic acids and heptanedioic acid exclusively gave nonconjugated 1,4-pentadiene; scale-up allowed the isolation of 1,15-hexadecadiene and 1,11-dodecadiene; the system represents a short and green route to terminal dienes from renewable dicarboxylic acids.
- Dennig, Alexander,Kurakin, Sara,Kuhn, Miriam,Dordic, Andela,Hall, Mélanie,Faber, Kurt
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supporting information
p. 3473 - 3477
(2016/07/29)
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- Why is RCM favoured over dimerisation? Predicting and estimating thermodynamic effective molarities by solution experiments and electronic structure calculations
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The thermodynamic effective molarities of a series of simple cycloalkenes, synthesised from α,ω-dienes by reaction with Grubbs' second generation precatalyst, have been evaluated. Effective molarities were measured from a series of small scale metathesis reactions and agreed well with empirical predictions derived from the number of rotors and the product ring strain. The use of electronic structure calculations (at the M06-L/6-311G* level of theory) was explored for predicting thermodynamic effective molarities in ring-closing metathesis. However, it was found that it was necessary to apply a correction to DFT-derived free energies to account for the entropic effects of solvation. Complete control: Can classical theory, developed for ring-closing metathesis (RCM) reactions that involve σ-bond formation, describe the thermodynamics of RCM reactions forming π bonds? Empirical theory and modern electronic structure calculations have been employed to predict the outcome of RCM reactions of simple α,ω-dienes with Grubbs' second generation pre-catalysts, resulting in mixtures of cycloalkenes and oligomers (see scheme). Copyright
- Nelson, David J.,Ashworth, Ian W.,Hillier, Ian H.,Kyne, Sara H.,Pandian, Shanthi,Parkinson, John A.,Percy, Jonathan M.,Rinaudo, Giuseppe,Vincent, Mark A.
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p. 13087 - 13094
(2012/01/02)
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- Regioselective synthesis of vic-halo alcohols and symmetrical or unsymmetrical vic-dihalides from epoxides using triphenylphosphine -N-halo imides
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A simple, novel, and highly regioselective cleavage of epoxides into vicinal halo alcohols and symmetrical or unsymmetrical dihalides is described using different stoichiometries of triphenylphosphine (PPh3) and N-halo succinimide (NXS) or N-halo saccharine (NXSac).
- Iranpoor, Nasser,Firouzabadi, Habib,Azadi, Roya,Ebrahimzadeh, Farzaneh
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- Semivolatile and volatile compounds in combustion of polyethylene
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The evolution of semivolatile and volatile compounds in the combustion of polyethylene (PE) was studied at different operating conditions in a horizontal quartz reactor. Four combustion runs at 500 and 850°C with two different sample mass/air flow ratios and two pyrolytic runs at the same temperatures were carried out. Thermal behavior of different compounds was analyzed and the data obtained were compared with those of literature. It was observed that α,ω-olefins, α-olefins and n-paraffins were formed from the pyrolytic decomposition at low temperatures. On the other hand, oxygenated compounds such as aldehydes were also formed in the presence of oxygen. High yields were obtained of carbon oxides and light hydrocarbons, too. At high temperatures, the formation of polycyclic aromatic hydrocarbons (PAHs) took place. These compounds are harmful and their presence in the combustion processes is related with the evolution of pyrolytic puffs inside the combustion chamber with a poor mixture of semivolatile compounds evolved with oxygen. Altogether, the yields of more than 200 compounds were determined. The collection of the semivolatile compounds was carried out with XAD-2 adsorbent and were analyzed by GC-MS, whereas volatile compounds and gases were collected in a Tedlar bag and analyzed by GC with thermal conductivity and flame ionization detectors.
- Font, Rafael,Aracil, Ignacio,Fullana, Andrés,Conesa, Juan A.
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p. 615 - 627
(2007/10/03)
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- High activity ruthenium or osmium metal carbene complexes for olefin metathesis reactions and synthesis thereof
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A method of preparing a catalyst of the formula comprising:reacting a compound of the formula (XX1MLnL1m)p with a phosphorane of the formula wherein:M is Os or Ru;R and R1 are either the same or different and are(a) hydrogen,(b) a group selected from C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 alkyl, aryl, C1-C20 carboxylate, C2-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl, or C1-C20 alkylsulfinyl, or(c) one of the groups listed in (b) substituted with C1-C5 alkyl, halogen, C1-C5 alkoxy, unsubstituted phenyl, halogen substituted phenyl, C1-C5 alkyl substituted phenyl, or C1-C5 alkoxy substituted phenyl;R4, R5, and R6 are either the same or different and are each unsubstituted or substituted hydrocarbon wherein the hydrocarbon is selected from the group consisting of aryl, C1-C6 alkyl, C1-C6 alkoxy, and phenoxy and the hydrocarbon substitution is selected from the group consisting of halogen, C1-C3 alkyl, C1-C3 alkoxy, unsubstituted phenyl, halogen substituted phenyl, C1-C5 alkyl substituted phenyl, and C1-C5 alkoxy substituted phenyl;X and X1 are either the same or different and are any anionic ligand;L is any neutral electron donor;L1 is a trialkylphosphine ligand where at least one of the alkyl groups is a secondary alkyl or a cycloalkyl;n and m are independently 0-4, provided n+m=2, 3 or 4; andp is an integer equal to or greater than 1.
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- Dilithium tetrachlorocuprate catalyzed coupling of allylmagnesium bromide with α,ω-dihaloalkanes
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Allylmagnesium bromide has been shown to cross-couple with α,ω- dihaloalkanes in the presence of dilithium tetrachlorocuprate to yield, depending on reaction conditions, mono-coupled haloalkenes or di-coupled alkadienes. The order of the reactivity of the dihalides is I > Br >> CI and secondary halides show greater reactivity than primary halides.
- Johnson,Donohoe,Kang
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p. 1557 - 1564
(2007/10/02)
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- On the Pyrolysis of Unsubstituted Cyclanes - Selectivity of the Formation of Reaction Products, Kinetic Parameters, Mechanistic Interpretations
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The thermal decomposition of cyclopentane (1), cyclohexane (2), cycloheptane (3), cyclooctane (4), cyclodecane (5), and cyclododecane (6) was studied in a laboratory-scale metallic tubular reactor at 650 to 850 deg C in the presence of steam.The kinetic parameters for the overall reactions were determined and the gaseous as well as the liquid reaction products were analyzed and identified by gas chromatography or by the coupling of gas chromatography and mass spectrometry, respectively.It could be shown that from all cyclanes the isomeric α-olefines are formed, if the conversion of the starting cyclanes is small.This supports the view that the cyclane - α-olefin isomerization is an important initial reaction in pyrolysis of 1 up to 6.The results also demonstrate that the main pathway of degradation is a radical chain mechanism via cyclanyl radicals with β(C-C) bond scission and 1.4 or 1.5-H-isomerization of alkenyl radicals as the most important reaction steps.
- Zimmermann, G.,Zychlinski, W.,Bach, G.,Rennecke, D.
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- FORMATION OF SOME BICYCLIC SYSTEMS BY RADICAL RING-CLOSURE
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The rates and stereochemistry of ring closure of the radicals (2), (9), (10), and (16) have been determined and rationalised.
- Beckwith, Athelstan L. J.,Phillipou, George,Serelis, Algirdas K.
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p. 2811 - 2814
(2007/10/02)
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- Reaction of Bicycloalkanes (n=3-6) with the Olefin-metathesis Catalysts Tungsten Hexachloride-Tetraphenyltin and Tungsten Hexachloride-Ethylaluminium Dichloride
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The title reaction does not yield the products of a retro-carbene addition reaction.The main products of the reaction of bicyclononane with these catalysts are methylenecyclo-octane and methylcyclo-octenes.
- Uchida, Akira,Hata, Kazuyuki
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p. 1111 - 1114
(2007/10/02)
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- Hydride Eliminations, VIII. - Note on Site-Specific Hydride Abstraction from Carbanions
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Reaction of lithium and magnesium alkyl compounds at -20 to 0 deg C with ethylene in the presence of nickel chloride leads under β-hydride abstraction to completely site-specific olefin formation.In stereochemically relevant cases the formation of the thermodynamically less stable Hofmann product is slightly preferred.
- Reetz, Manfred T.,Stephan, Wilfried
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p. 171 - 173
(2007/10/02)
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