- Impact of the Spatial Organization of Bifunctional Metal–Zeolite Catalysts on the Hydroisomerization of Light Alkanes
-
Improving product selectivity by controlling the spatial organization of functional sites at the nanoscale is a critical challenge in bifunctional catalysis. We present a series of composite bifunctional catalysts consisting of one-dimensional zeolites (ZSM-22 and mordenite) and a γ-alumina binder, with platinum particles controllably deposited either on the alumina binder or inside the zeolite crystals. The hydroisomerization of n-heptane demonstrates that the catalysts with platinum particles on the binder, which separates platinum and acid sites at the nanoscale, leads to a higher yield of desired isomers than catalysts with platinum particles inside the zeolite crystals. Platinum particles within the zeolite crystals impose pronounced diffusion limitations on reaction intermediates, which leads to secondary cracking reactions, especially for catalysts with narrow micropores or large zeolite crystals. These findings extend the understanding of the ??intimacy criterion” for the rational design of bifunctional catalysts for the conversion of low-molecular-weight reactants.
- Cheng, Kang,Harmel, Justine,Oenema, Jogchum,Sunley, Glenn,Yoshida, Hideto,Ze?evi?, Jovana,Zhang, Zhaorong,de Jong, Krijn P.,van der Wal, Lars I.
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supporting information
p. 3592 - 3600
(2020/02/05)
-
- Preparation method of branched alkane (by machine translation)
-
The preparation method of the branched alkane disclosed by the invention comprises, the following steps: under. a protective atmosphere condition, mixing the alkyl alcohol intermediate with an: alkyl metal reagent and an, organic solvent, to obtain the branched alkane, and the method disclosed by, the invention is; simple in synthesis route, high in yield and, high in, purity. (by machine translation)
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-
-
- GAS-TO-LIQUID REACTOR AND METHOD OF USING
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A device and a process to propagate molecular growth of hydrocarbons, either straight or branched chain structures, that naturally occur in the gas phase to a molecular size sufficient to shift the natural occurring phase to a liquid or solid state is provided. According to one embodiment, the device includes a grounded reactor vessel having a gas inlet, a liquid outlet, and an electrode within the vessel; a power supply coupled to the electrode for creating an elecirostatic field within the vessel for converting the gas to a liquid and or solid state.
- -
-
Paragraph 0140-0142
(2019/08/15)
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- Conversion of dimethyl ether to 2,2,3-trimethylbutane over a Cu/BEA catalyst: Role of Cu sites in hydrogen incorporation
-
Recently, it has been demonstrated that methanol and/or dimethyl ether can be converted into branched alkanes at low temperatures and pressures over large-pore acidic zeolites such as H-BEA. This process achieves high selectivity to branched C4 (e.g., isobutane) and C7 (e.g., 2,2,3-trimethylbutane) hydrocarbons. However, the direct homologation of methanol or dimethyl ether into alkanes and water is hydrogen-deficient, resulting in the formation of unsaturated alkylated aromatic residues, which reduce yield and can contribute to catalyst deactivation. In this paper we describe a Cu-modified H-BEA catalyst that is able to incorporate hydrogen from gas-phase H2 cofed with dimethyl ether into the desired branched alkane products while maintaining the high C4 and C7 carbon selectivity of the parent H-BEA. This hydrogen incorporation is achieved through the combination of metallic Cu nanoparticles present on the external surface of the zeolite, which perform H2 activation and olefin hydrogenation, and Lewis acidic ion-exchanged cationic Cu present within the H-BEA pores, which promotes hydrogen transfer. With cofed H2, this multifunctional catalyst achieved a 2-fold increase in hydrocarbon productivity in comparison to H-BEA and shifted selectivity toward products favored by the olefin catalytic cycle over the aromatic catalytic cycle.
- Schaidle, Joshua A.,Ruddy, Daniel A.,Habas, Susan E.,Pan, Ming,Zhang, Guanghui,Miller, Jeffrey T.,Hensley, Jesse E.
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p. 1794 - 1803
(2015/03/14)
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- Synthesis and hydrogenation activity of iron dialkyl complexes with chiral bidentate phosphines
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The activity of bis(phosphine) iron dialkyl complexes for the asymmetric hydrogenation of alkenes has been evaluated. High-throughput experimentation was used to identify suitable iron-phosphine combinations using the displacement of pyridine from py2Fe(CH2SiMe3)2 for precatalyst formation. Preparative-scale synthesis of a family of bis(phosphine) iron dialkyl complexes was also achieved using both ligand substitution and salt metathesis methods. Each of the isolated organometallic iron complexes was established as a tetrahedral and hence high-spin ferrous compound, as determined by M?ssbauer spectroscopy, magnetic measurements, and, in many cases, X-ray diffraction. One example containing a Josiphos-type ligand, (SL-J212-1)Fe(CH2SiMe3)2, proved more active than other isolated iron dialkyl precatalysts. Filtration experiments and the lack of observed enantioselectivity support dissociation of the phosphine ligand upon activation with dihydrogen and formation of catalytically active heterogeneous iron. The larger six-membered chelate is believed to reduce the coordination affinity of the phosphine for the iron center, enabling metal particle formation.
- Hoyt, Jordan M.,Shevlin, Michael,Margulieux, Grant W.,Krska, Shane W.,Tudge, Matthew T.,Chirik, Paul J.
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p. 5781 - 5790
(2015/02/19)
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- Mechanistic details of acid-catalyzed reactions and their role in the selective synthesis of triptane and isobutane from dimethyl ether
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We report here kinetic and isotopic evidence for the elementary steps involved in dimethyl ether (DME) homologation and for their role in the preferential synthesis of 2,2,3-trimethylbutane (triptane) and isobutane. Rates of methylation of alkenes and of hydrogen transfer, isomerization and β-scission reactions of the corresponding alkoxides formed along the homologation path to triptane were measured using mixtures of 13C-labeled dimethyl ether (13C-DME) and unlabeled alkenes on H-BEA. DME-derived C1 species react with these alkenes to form linear butyls from propene, isopentyls from n-butenes, 2,3-dimethylbutyls from isopentenes, and triptyls from 2,3-dimethylbutenes; these kinetic preferences reflect the selective formation of the more highly substituted carbenium ions and the retention of a four-carbon backbone along the path to triptane. Hydrogen transfer reactions terminate chains as alkanes; chain termination probabilities are low for species along the preferred methylation path, but reach a maximum at triptyl species, because tertiary carbenium ions involved in hydrogen transfer are much more stable than those with primary character required for triptene methylation. Alkenes and alkanes act as hydrogen donors and form unsaturated species as precursors to hexamethylbenzene, which forms to provide the hydrogen required for the DME-to-alkanes stoichiometry. Weak allylic C-H bonds in isoalkenes are particularly effective hydrogen donors, as shown by the higher termination probabilities and 12C content in hexamethylbenzene as 12C-2-methyl-2-butene and 12C-2,3-dimethyl-2-butene pressures increased in mixtures with 13C-DME. The resulting dienes and trienes can then undergo Diels-Alder cyclizations to form arenes as stable by-products. Isomerization and β-scission reactions of the alkoxides preferentially formed in methylation of alkenes are much slower than hydrogen transfer or methylation rates, thus preventing molecular disruptions along the path to triptane. Methylation at less preferred positions leads to species with lower termination probabilities, which tend to grow to C8+ molecules; these larger alkoxides undergo facile β-scission to form tert-butoxides that desorb preferentially as isobutane via hydrogen transfer; such pathways resolve methylation "missteps" by recycling the carbon atoms in such chains to the early stages of the homologation chain and account for the prevalence of isobutane among DME homologation products. These findings were motivated by an inquiry into the products formed via C1 homologation, but they provide rigorous insights about how the structure and stability of carbenium ions specifically influence the rates of methylation, hydrogen transfer, β-scission, and isomerization reactions catalyzed by solid acids.
- Simonetti, Dante A.,Ahn, John H.,Iglesia, Enrique
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experimental part
p. 173 - 195
(2011/03/17)
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- PROCESS FOR THE PRODUCTION OF A HYDROCARBON
-
A method of alkane homologation is provided, comprising contacting: a reactive alkane; a methylating agent; an optional diamondoid modifier; and an activating catalyst, thereby generating a hydrocarbon product having a greater number of carbon atoms than the reactive alkane.
- -
-
Page/Page column 21-23
(2009/06/27)
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- Selective methylative homologation: An alternate route to alkane upgrading
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InI3 catalyzes the reaction of branched alkanes with methanol to produce heavier and more highly branched alkanes, which are more valuable fuels. The reaction of 2,3-dimethylbutane with methanol in the presence of InI3 at 180-200°C affords the maximally branched C7 alkane, 2,2,3-trimethylbutane (triptane). With the addition of catalytic amounts of adamantane the selectivity of this transformation can be increased up to 60%. The lighter branched alkanes isobutane and isopentane also react with methanol to generate triptane, while 2-methylpentane is converted into 2,3-dimethylpentane and other more highly branched species. Observations implicate a chain mechanism in which InI3 activates branched alkanes to produce tertiary carbocations which are in equilibrium with olefins. The latter react with a methylating species generated from methanol and InI 3 to give the next-higher carbocation, which accepts a hydride from the starting alkane to form the homologated alkane and regenerate the original carbocation. Adamantane functions as a hydride transfer agent and thus helps to minimize competing side reactions, such as isomerization and cracking, that are detrimental to selectivity.
- Bercaw, John E.,Hazari, Nilay,Labinger, Jay A.,Scott, Valerie J.,Sunley, Glenn J.
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scheme or table
p. 11988 - 11995
(2009/02/05)
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- Hydrocarbon separation
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Process for the separation of close boiling compounds comprising distilling a hydrocarbon mixture of said compounds in the presence of a high boiling diluent liquid and a solid adsorbent. The high boiling diluent is withdrawn from the bottom of the distillation column and recycled to the column. The process is particularly suitable for the separation of straight-chain isomers from isomerate mixtures, the separation of benzene from hydrocarbon mixtures and the separation of paraffins from olefins.
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-
Page/Page column 11
(2008/12/06)
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- PROCESS FOR THE PRODUCTION OF A HYDROCARBON
-
A process for the production of a hydrocarbon which comprises contacting, in a reactor, methanol and/or dimethyl ether with a catalyst comprising a metal halide, such as a zinc halide, in which the methanol and/or dimethyl ether is contacted with the catalyst in the presence of at least one phosphorus compound having at least one P-H bond.
- -
-
Page/Page column 24-26
(2008/06/13)
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- Process for the preparation of a paraffin isomerization catalyst
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A process for preparation of a paraffin isomerization catalyst comprising a mixture of a Group IVB metal oxide, a Group VIB metal oxide, a Group IIIA metal oxide and a Group VIII metal. The process includes the steps of: a) contacting a hydroxide of the Group IVB metal with an aqueous solution of an oxyanion of the Group VIB metal to provide a mixture, (b) drying the mixture to provide a dry powder, (c) kneading the powder with a Group IIIA hydroxide gel and a polymeric cellulose ether compound to form a paste, (d) shaping the paste to form a shaped material, (e) calcining the shaped material to form a calcined material, (f) impregnating the calcined material with an aqueous solution of a Group VIII metal salt to provide the catalyst, and (g) calcining the catalyst.
- -
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Page/Page column 4-5
(2008/06/13)
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- Isomerization of N-heptane in naphtha cuts
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A process for the isomerization of normal heptane contained within a naphtha stream, such as a C6-C8 naphtha, in which the naphtha stream is fractionated into a fraction substantially free of normal heptane and a fraction containing normal heptane. The fraction containing normal heptane is contacted with an isomerization catalyst in an isomerization zone operated as a singe pass fixed bed reactor having a single effluent to isomerize a portion of said normal heptane to branched heptane. The effluent is recovered from said isomerization zone and the effluent is fractionated to recover said branched heptane. The unconverted normal heptane is recovered and returned to the isomerization since it can be separated from the branded heptanes by fractionation.
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Page/Page column 4
(2008/06/13)
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- Enhanced selectivity in the conversion of methanol to 2,2,3-trimethylbutane (triptane) over zinc iodide by added phosphorous or hypophosphorous acid
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The yield of triptane from the reaction of methanol with zinc iodide is dramatically increased by addition of phosphorous or hypophosphorous acid, via transfer of hydride from a P-H bond to carbocationic intermediates. The Royal Society of Chemistry.
- Bercaw, John E.,Grubbs, Robert H.,Hazari, Nilay,Labinger, Jay A.,Li, Xingwei
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p. 2974 - 2976
(2008/02/11)
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- Paraffin alkylation
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A liquid acid process is disclosed in which a hydrocarbon component containing an olefin, an olefin precursor or mixture and an isoalkane and a liquid acid catalyst is fed to a downflow reaction zone containing a disperser, under conditions to induce pulse flow at or near the outlet to react the isoalkane and olefin to produce a reaction product and feeding the reaction product to a vaporization zone containing a disperser under conditions to induce pulse flow at or near the outlet of the vaporization zone. A pressure drop across the disperser in the vaporization zone causes partial vaporization of the hydrocarbon which quench es the heat reaction and cooling the unvaporized portion of said reaction product, which is recovered and allowed to separate into an acid phase and hydrocarbon phase containing the alkylate. The acid catalyst and hydrocarbons may be fractally fed to the reaction zone.
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Page/Page column 7
(2008/06/13)
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- PROCESS
-
The present invention relates to a process for the production of branched chain hydrocarbons from methanol and/or dimethyl ether, which process comprises contacting, in a reactor, methanol and/or dimethyl ether with a catalyst comprising metal halide selected from rhodium halide, iridium halide and combinations thereof.
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Page/Page column 12; 13
(2008/06/13)
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- Alkylation process with recontacting in settler
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A system and/or process for decreasing the level of at least one organic fluoride present in a hydrocarbon phase contained in an alkylation settler by contacting the hydrocarbon phase with an HF containing stream, containing greater than about 80 wt. % and less than about 94 wt. % HF, in the intermediate portion of the settler which contains at least one tray system, with each tray system comprising a perforated tray defining a plurality of perforations and a layer of packing below the perforated tray, are disclosed.
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Page/Page column 3-5
(2008/06/13)
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- On the mechanism of the conversion of methanol to 2,2,3-trimethylbutane (triptane) over zinc iodide
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Methanol is converted to a mixture of hydrocarbons by reaction with zinc iodide at 200 °C with one highly branched alkane, 2,2,3-trimethylbutane (triptane), being obtained in surprisingly high selectivity. Mechanistic studies implicate a two-stage process, the first involving heterogeneously catalyzed formation of a carbon-carbon-bonded species, probably ethylene, that undergoes homogeneously catalyzed sequential cationic methylation to higher hydrocarbons. The first stage can be bypassed by addition of olefins, higher alcohols, or arenes, which act as initiators. Rationales for the particular activity of zinc iodide and for the selectivity to triptane are proposed.
- Bercaw, John E.,Diaconescu, Paula L.,Grubbs, Robert H.,Kay, Richard D.,Kitching, Sarah,Labinger, Jay A.,Li, Xingwei,Mehrkhodavandi, Parisa,Morris, George E.,Sunley, Glenn J.,Vagner, Patrick
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p. 8907 - 8917
(2007/10/03)
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- PYRIDOPYRAZINES FOR COMBATTING PHYTOPATHOGENIC FUNGI
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The compounds of the general formula (I) wherein R, R1, R2, R8, and R9 are defined as set forth in the specification.
- -
-
Page/Page column 13-14
(2008/06/13)
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- Disproportionation of hydrocarbons
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A novel hydrocarbon disproportionation process is provided and includes contacting a hydrocarbon feed comprising at least one paraffin with a disproportionation catalyst comprising a support component, a metal, and a halogen in a disproportionation reaction zone under disproportionation reaction conditions.
- -
-
-
- C7+ paraffin isomerisation process and catalyst therefore
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There is provided a process for selective isomerisation of C4+ paraffins using a catalyst comprising mixed aluminium, tungsten and zirconium oxides, and a hydrogenation/dehydrogenation component, such as palladium or other Group VIII metals. The feed may optionally also include shorter paraffins, aromatics or cycloparaffins.
- -
-
-
- Catalyst and process for contacting a hydrocarbon and ethylene
-
A process of contacting at least one feed hydrocarbon, containing three to about seven carbon atoms per molecule, and ethylene in a hydrocarbon-containing fluid in the presence of a catalyst composition to provide at least one product hydrocarbon isomer containing about four to about nine carbon atoms per molecule is provided. The at least one feed hydrocarbon can be selected from paraffins, isoparaffins, and the like and combinations thereof. The catalyst composition contains a hydrogen halide component, a sulfone component, and a metal halide component.
- -
-
-
- METHOD FOR THE PRODUCTION OF NON-AROMATIC HYDROCARBONS
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The invention relates to a method for the production of long-chain, branched-chain and/or cyclic hydrocarbons. A low molecular weight alkyl halide and a fused salt are firstly prepared. The fused salt contains an electrophilic compound and a reducing agent and is free from oxygen and oxygen compounds. The alkyl halide is then brought into contact with the fused salt such that long-chain, branched-chain and/or cyclic hydrocarbons are formed in the fused salt. The hydrocarbons formed in the fused salt are drawn off and can subsequently be separated from unreacted starting materials. By means of the above method, hydrogen can be produced during the reaction of the low molecular weight alkyl halide. The risk of oxidation of the alkane produced to give carbon monoxide or carbon dioxide is avoided by means of the reducing conditions in the fused salt. The product distribution can be controlled by means of suitable selection of the composition of the fused salt. Highly-branched hydrocarbons are produced with the preferred application of a sodium chloroaluminate fused salt.
- -
-
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- Process of paraffin hydrocarbon isomerisation catalysed by an ionic liquid in the presence of a cyclic hydrocarbon additive
-
A process for the conversion of linear and/or branched paraffins hydrocarbons, catalysed by an ionic liquid catalyst, in the presence of a cyclic hydrocarbon additive containing a tertiary carbon atom. The presence of the specific hydrocarbon additives influences the reaction mechanism by increasing the selectivity towards the formation of paraffin hydrocarbons with a higher degree of branching.
- -
-
-
- Isomerisation process
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A process for the production of triptane, said process comprising: isomerising a hydrocarbon feedstock by containing said feedstock with an isomerisation catalyst at a reaction temperature of ?50 to 25° C., and a contact time of 0.01 to 150 hours, such that the triptane selectivety of the isomerisation reaction is at least 5% as a proportion of said hydrocarbon feedstock.
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Page/Page column 4
(2008/06/13)
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- Gas to liquid conversion process
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A process is disclosed for the conversion of lower molecular weight hydrocarbons, such as methane, into higher molecular weight hydrocarbon products, such as hydrocarbons having between 4 and 29 carbons. The process includes forming hydrated electrons, such as by mixing the lower molecular weight hydrocarbons with water and contacting the mixture with an energy source to form hydrated electrons. The hydrated electrons react with the methane to form hydrogen and higher molecular weight hydrocarbon products. Also disclosed is a related process for converting higher molecular weight hydrocarbons to lower molecular weight hydrocarbons by forming a mixture of higher molecular weight hydrocarbons and water and contacting the mixture with an energy source to form hydrated electrons that react with the higher molecular weight hydrocarbons to form hydrogen and lower molecular weight hydrocarbon products.
- -
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Page column 3-4
(2008/06/13)
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- Hydrogenolysis and Homologation of 3,3-Dimethyl-1-butene on Ru/SiO2 Catalyst: Implications for the Mechanism of Carbon-Carbon Bond Formation and Cleavage on Metal Surfaces
-
The reactions of 3,3-dimethyl-1-butene (neohexene) with hydrogen in the presence of zero-valent ruthenium metal particles supported on silica are reported.The predominant reaction is the hydrogenation of neohexene to neohexane.Simultaneous but slower homologation and hydrogenolysis reactions are reported.The homologation and hydrogenolysis reactions run at approximately equal rates, suggesting a mechanistic link between the two processes.The relative quantities of C1-C5 and C7 products and the variation of these quantities with respect to varying temperature, neohexene/ hydrogen ratio, and contact time are reported.The distribution of the primary products, neopentane, isobutene, and methane for hydrogenolysis and 2,2-dimethyl pentane, 2,2,3-trimethyl butane, and 4,4-dimethyl-1-pentene for homologation is discussed in terms of current thought on the mechanism of homologation and hydrogenolysis of alkanes.The most likely and strongly indicated mechanism for the hydrogenolysis of neohexene involves the deinsertion of a methylidene fragment from a ruthenium-neohexyl intermediate which is also an intermediate in the hydrogenation of neohexene.The distribution of C7 homologation products does not allow one to distinguish between a simple insertion mechanism and a mechanism passing through a metallacyclic intermediate.
- Toyir, Jamil,Leconte, Michel,Niccolai, Gerald P.,Basset, Jean-Marie
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p. 306 - 312
(2007/10/02)
-
- Site segregation in small rhodium bimetallic aggregates: A combined catalytic and quantum chemical study
-
The spatial distribution of the two components at the surface of small bimetallic aggregates has been investigated by using the hydrogenolysis of model alkanes and quantum chemical calculations. The catalysts were supported on γ-alumina and consisted of rhodium particles (size ? 1-2 nm), modified by Sn, Pb, Sb, or Ge. They were prepared by using the surface reaction of rhodium hydride with organometallic compounds. On pure Rh catalysts, the conversions of n-hexane and methylcyclopentane show a low sensitivity to changes of the surface topology, corresponding either to a modification of the particle size or to the addition of a small amount of Sn or Ge modifier. At variance, the hydrogenolysis of 2,2,3,3-tetramethylbutane is highly sensitive to the topology of the surface and yields selectively 2,2,3-trimethylbutane and methane on small particles, which have mainly sites of low coordination (corners and edges), whereas isobutane is selectively formed on large particles, which show more sites of high coordination (facets, planes). The addition of a small amount of Sn or Pb favors the formation of isobutane, but the addition of an equivalent amount of Ge promotes demethylation. Therefore, Sn and Pb inhibit selectively the reactions catalyzed by the sites of low coordination, and this demonstrates that there is a topological segregation to these sites, while Ge atoms appear to be randomly distributed at the surface. Quantum chemical calculations of the relative stabilities of Rh10M4, Rh10M3, and Rh12M model clusters (M = Sn, Ge), with different geometries and different localizations of M, support the conclusion that the most stable aggregates are those where the M atoms are localized at the periphery. However, Sn atoms are shown to segregate essentially to the corner sites, whereas Ge atoms do not have as definite a preference. Moreover, Ge differs from Sn in the sense that Ge atoms tend to disperse in the Rh lattice, while Sn atoms tend to form Sn-Sn bonds.
- Coq, Bernard,Goursot, Annick,Tazi, Touria,Figuéras, Francois,Salahub, Dennis R.
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p. 1485 - 1492
(2007/10/02)
-
- Reductive Alkylation and Reduction of Tertiary, Secondary, and Benzylic Alcohols with Trimethyl-, Triethyl-, and Triisopropylboron/Trifluoromethanesulfonic (Triflic) Acid
-
Tertiary, secondary, and benzylic alcohols were reductively alkylated and reduced with trimethyl-, triethyl-, and triisopropylboron/trifluoromethanesulfonic (triflic) acid.A postulated mechanism for the reactions is discussed.
- Olah, George A.,Wu, An-hsiang,Farooq, Omar
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p. 2759 - 2761
(2007/10/02)
-
- Ring-opening of Alkyl-substituted Cyclopropanes in the Presence of Hydrogen on Copper
-
In the presence of hydrogen on copper, the cyclopropanes (1), (2), and (3) are transformed into saturated hydrocarbons containing the same number of carbon atoms (alkenes are also formed, through isomerization of the cyclopropanes); these studies reveal the importance of a previously unknown property of copper in heterogeneous metal catalysis.
- Bartok, Mihaly,Palinko, Istvan,Molnar, Arpad
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p. 953 - 954
(2007/10/02)
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- Isomerisation des radicaux insatures. IV. Les radicaux methyl-1-, methyl-2- et dimethyl-1,2-propene-1 yles produit dans la photolyse des tri- et tetramethylethylenes a 147 nm
-
Direct photolysis at 147 nm of tri- and tetramethylethylenes has been used to produce highly excited vinylic 1-methyl- and 2-methyl-1-propene-1-yl radicals (C4H7), as well as the 1,2-dimethyl-1-propen-1-yl radical (C5H9).In both cases, the primary fragmentation of the photoexcited molecules involved the split of an α(C-C) bond with high yields.The excess energy is sufficiently important that the majority of the vinylic radicals are very hot, and are able to isomerize towards an allylic structure before the occurence of fragmentation.At a pressure of a few Torr, most of the vinylic C4H7 radicals (ca. 70percent) isomerize to an allylic structure, and its lifetime is estimated to be less than one nanosecond under the present conditions.Although the mechanism is less simple, the excited vinylic C5H9 radical exhibits similar behaviour.
- Collin, Guy J.,Deslauriers, Helene,Mare, George R. De
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p. 391 - 396
(2007/10/02)
-
- CONTRIBUTION A L'ETUDE DES REACTIONS DE COMBINAISON DES RADICAUX ALCOYLE TERTIAIRES EN PHASE SOLIDE
-
Disproportionation/combination ratios of self-reacting t-alkyl radicals are estimated in solid phase at low temperature.The low temperature solid state limit was estimated to be 7-25, this value is considerably lower than ratios of the literature (100 to 500) and is compatible with the FISCHER limit in liquid state.In the present work, the ratios are determined by product analysis from the gamma radiolysis of isobutane.
- Gourdin-Serveniere, C.,Fontaine, L. M.,Tilquin, B.
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p. 177 - 188
(2007/10/02)
-
- THE PHOTOLYSIS OF 2,3- AND 3,3-DIMETHYL-1-BUTENE AT 147.0 AND 184.9 nm
-
The photofragmentation of 2,3-dimethylbutene and 3,3-dimethylbutene has been studied at 147 and 184.9 nm in the gas phase.The main primary decomposition process at both wavelengths involves the rupture of a β(C-C) bond.The quantum yield for this process is higher than 0.7 at 147 nm and is probably even higher at 184.9 nm.All dimethyallyl radicals formed at 147 nm in this process decompose at low pressure, but some of them isomerize from the α,β- to the α,α- structure (and vice versa) - via a 1,4-H transfer - before decomposition.At 184.9 nm, the same primary process is used to get a rough value for the lifetime of the photoexcited molecule, compared with the one made RRKM calculations by assuming that all the photon energy resides in the vibrational framework of the fundamental electronic state.These lifetimes are about one nanoseconde or less.
- Deslauriers, Helene,Collin, Guy J.
-
-
- Thermolabile Hydrocarbons, XXI. Relationships between Thermal Stability and Strain of Non-Symmetrical Highly Branched Hydrocarbons
-
The pyrolysis reaction of 20 hydrocarbons 3 into radicals 4 and tert-butyl radicals was investigated by product analysis and kinetics.It is shown that the same relationships between the free enthalpies of activation and the strain energies observed earlier for the cleavage of symmetrically substituted CC bonds are valid for the cleavage of unsymmetrical substituted bonds.The introduction of the new concept "strain energy of dissociation" (difference in strain between the ground state 3 and the residual strain in the radical fragments 4 and 5) has proven to be particularly useful.It is now possible to predict the rate of homolytic cleavage of almost all simple CC bonds by force field calculations.
- Hellmann, Siegried,Beckhaus, Hans-Dieter,Ruechardt, Christoph
-
p. 2238 - 2249
(2007/10/02)
-
- THE PREPARATION OF HINDERED CUPRATES FROM ALDEHYDE TOSYLHYDRAZONES
-
Copper reagents react with secondery and tertiary aldehyde tosylhydrazones to give unique, hindered cuprates which are alkylated in a one-flask procedure.
- Bertz, Steven H.
-
p. 3151 - 3154
(2007/10/02)
-
- Thermolabile Hydrocarbons, XIV. Thermal Stability, Strain Enthalpy, and Structure of sym. Hexaalkyl-substituted Ethanes
-
Activation parameters were determined for the thermolysis reaction of thirteen sym. hexaalkyl-substituted ethanes (Cq-Cq-series).From product analyses it was concluded that the central Cq-Cq-bond is cleaved in the rate determining step by homolysis.A reasonable relationship between the free enthalpy of activation ΔG* (300 deg C) of the reactions and steric substituent constants φfwas observed.Much better correlations were found between ΔG* (300 deg C) and strain enthalpies HS of the hydrocarbons as obtained from molecular mechanics calculations.From the slope of these correlations it is deduced that 40percent residual strain is still present at transition state of these C-C-cleavage reactions.The structural data calculated using Allinger's MM2 force field are distinguished by long central Cq-Cq-bonds (up to 164.1 pm), by large angle deformations on α-C-atoms of side chains and by deviations from the ideal torsional angle Θ = 180 deg along the central bond.The central Cq-Cq-bond length increases in a linear manner with increasing strain enthalpy HS.
- Winiker, Robert,Beckhaus, Hans-Dieter,Ruechardt, Christoph
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p. 3456 - 3476
(2007/10/02)
-
