1192-18-3Relevant academic research and scientific papers
EVIDENCE FOR A SINGLE ELECTRON TRANSFER MECHANISM IN REACTIONS OF LITHIUM DIORGANOCUPRATES WITH ORGANIC HALIDES
Ashby, E. C.,DePriest, R. N.,Tuncay, A.,Srivastava, Sushil
, p. 5251 - 5254 (1982)
It has been demonstrated by means of spectroscopic studies involving cyclizable alkyl halides that lithium dimethylcuprate can react with organic halides by a single electron transfer pathway.
CONCERNING THE REDUCTION OF ALKYL HALIDES BY LiAlH4. EVIDENCE THAT AlH3 PRODUCED IN SITU IS THE ONE ELECTRON TRANSFER AGENT.
Ashby, E. C.,DePriest, R. N.,Pham, T. N.
, p. 2825 - 2828 (1983)
The reduction of 10 and 20 alkyl iodides by LiAlH4 has been shown to involve a radical intermediate formed by the reaction of the alkyl iodide with the AlH3 and LiI produced in situ in conjunction with LiAlH4 rather than by LiAlH4 alone, as evidenced by cyclized products in the reduction of 6-iodo-1-heptene, by the trapping of the radical and by stereochemical studies of the 2-halooctanes.
Study of Ir/WO3/ZrO2-SiO2 ring-opening catalysts: Part II. Reaction network, kinetic studies and structure-activity correlation
Lecarpentier, Sebastien,van Gestel, Jacob,Thomas, Karine,Gilson, Jean-Pierre,Houalla, Marwan
, p. 49 - 63 (2008)
The present paper is the second part of a systematic study of the influence of W and Ir loading on the activity of Ir/WO3/ZrO2-SiO2 catalysts for the ring-opening reaction of naphthenic molecules using methylcyclohexane (MCH) as a model compound. A series of Si-stabilized tungstated zirconias, WOx/ZrO2-SiO2, containing up to 3.5 atom W/nm2, was prepared. Ir-based catalysts containing up to 1.2 wt% were obtained by impregnation of these solids. Characterization of the metal dispersion and catalyst acidity was described in a previous article. The objective of the present study was to determine the best metal/acid balance for optimal performance of Ir/WOx/ZrO2-SiO2 catalysts in the ring-opening reaction of MCH. Monofunctional (acid WOx/ZrO2-SiO2 or metal Ir/ZrO2-SiO2) and bifunctional (Ir/WO3/ZrO2-SiO2) catalysts were examined. Based on the analysis of the yields and products distributions, a reaction network was proposed, and kinetic data (e.g., activation energies, initial rates) were calculated. Correlations between characterization results obtained earlier (e.g., acidity, dispersion) and catalytic performance are also reported. The monofunctional acid catalysts WOx/ZrO2-SiO2 showed a low selectivity for ring opening. The ring-contraction activity developed for W surface density above a threshold value of 1 atom W/nm2. This was attributed to the appearance and the development of a relatively strong Broensted acidity monitored by infrared measurements. MCH ring contraction and C5 naphthene ring opening occur according to a classic acid mechanism. For low conversions, the monofunctional metal catalysts Ir/ZrO2-SiO2 exhibited significant selectivity for ring opening that decreased with increasing conversion. Because of the lack of ring-contraction products, the observed activity was attributed to the direct ring opening of the MCH. Ring opening and cracking occur according to a dicarbene mechanism. The study of MCH conversion on Ir/WOx/ZrO2-SiO2 catalysts indicated that MCH ring contraction to alkylcyclopentanes occurs before ring opening. The best yields for ring opening were obtained with the 1.2% Ir/WOx/ZrO2 (1.5 atom of W/nm2). Further increases in W surface density led to a decrease in the indirect ring-opening yield, attributed to a decrease in Ir dispersion. For bifunctional metal/acid catalysts, analysis of the mechanism is less straightforward. The activation energy for C6 ring contraction and indirect C6 ring opening is a function of the metal/acid ratio. For high ratios, indirect ring opening occurs essentially over metallic sites. A decrease in the metal/acid ratio enhances the contribution of acid mechanism.
Stereoselectivity of Ring Closure of Substituted Hex-5-enyl Radicals
Beckwith, Athelstan L. J.,Lawrence, Tony,Serelis, Algirdas K.
, p. 484 - 485 (1980)
1,5-Ring closure of 1- or 3-substituted hex-5-enyl radicals affords mainly cis-disubstituted cyclic products, whereas 2- or 4-substituted species give mainly trans-products; the significance of this stereoselectivity is demonstrated in the formation of the norbornane system from acyclic precursors.
SUPPRESSING THE CYCLIZATION OF (1-METHYL-5-HEXENYL)SODIUM
Garst, John F.,Hines, John B.,Bruhnke, John D.
, p. 1963 - 1966 (1986)
In reactions of 1-methyl-5-hexenyl chloride and bromide with sodium metal and sodium naphthalene in DME and THF, the cyclization of (1-methyl-5-hexenyl)sodium is suppressed by added tert-butylamine.Since the cyclization of 1-methyl-5-hexenyl radical does not appear to be affected, this demonstrates the practicality of using the 1-methyl-5-hexenyl group as a probe for radical intermediates in the presence of tert-butylamine.
A novel reduction of polycarboxylic acids into their corresponding alkanes using n-butylsilane or diethylsilane as the reducing agent
Nimmagadda, Rama D.,McRae, Christopher
, p. 3505 - 3508 (2006)
A convenient one-pot reaction has been developed for the reduction of polycarboxylic acids on aliphatic and aromatic systems to their corresponding alkanes. The reduction utilises either diethylsilane or n-butylsilane as the reducing agent in the presence of the Lewis acid catalyst tris(pentafluorophenyl)borane.
Rate Constants and Arrhenius Parameters for the Reactions of Some Carbon-Centered Radicals with Tris(trimethylsilyl)silane
Chatgilialoglu, C.,Dickhaut, J.,Giese, B.
, p. 6399 - 6403 (1991)
Rate constants for the reactions of some carbon-centered radicals with (Me3Si)3SiH have been measured over a range of temperatures by using competing unimolecular radical reactions as timing devices.For example, the rate constants (at 298 K) are 3.7, 1.4, and 2.6 x 1E5 M-1 s-1 from primary, secondary, and tertiary alkyl radicals, respectively.Comparison of the radical trapping abilities of tri-n-butylstannane and tris(trimethylsilyl)silane is discussed.The use of 1,1-dimethyl-5-hexenyl cyclization as a radical clock has been recalibrated by using new data and data from the literature.
Kinetics for the Reaction of a Secondary Alkyl Radical with Tri-n-butylgermanium Hydride and Calibration of a Secondary Alkyl Radical Clock Reaction
Lusztyk, J.,Maillard, B.,Deycard, S.,Lindsay, D. A.,Ingold, K. U.
, p. 3509 - 3514 (1987)
Arrhenius parameters for the reaction of a secondary alkyl radical with tri-n-butylgermanium hydride have been measured by using the cyclization of 1-methyl-5-hexenyl radical as a "clock" reaction.At 298 K the rate constant is 1.8*104 M-1s-1, which makes the secondary alkyl radical/n-Bu3GeH reaction about 80 times slower than the corresponding reaction with tri-n-butyltin hydride.The secondary alkyl radical clock reaction has been rather precisely calibrated by using new data and data from the literature.At attempt to carry out similar experiments with 1,1-dimethyl-5-hexenyl yielded much less precise data for the cyclization o f this tertiary alkyl radical.Reliable kinetic data for hydrogen abstraction from n-Bu3GeH by tertiary alkyl radicals could not be obtained by using either the parent bromide or appropriate N-hydroxypyridine-2-thione esters as alkyl radical sources.
Insights into the Major Reaction Pathways of Vapor-Phase Hydrodeoxygenation of m-Cresol on a Pt/HBeta Catalyst
Sun, Qianqian,Chen, Guanyi,Wang, Hua,Liu, Xiao,Han, Jinyu,Ge, Qingfeng,Zhu, Xinli
, p. 551 - 561 (2016/02/20)
Conversion of m-cresol was studied on a Pt/HBeta catalyst at 225-350°C and ambient hydrogen pressure. At 250°C, the reaction proceeds through two major reaction pathways: (1) direct deoxygenation to toluene (DDO path); (2) hydrogenation of m-cresol to methylcyclohexanone and methylcyclohexanol on Pt, followed by fast dehydration on Br?nsted acid sites (BAS) to methylcyclohexene, which is either hydrogenated to methylcyclohexane on Pt or ring-contracted to dimethylcyclopentanes and ethylcyclopentane on BAS (HYD path). The initial hydrogenation is the rate-determining step of the HYD path as its rate is significantly lower than those of subsequent steps. The apparent activation energy of the DDO path is 49.7 kJ mol-1 but the activation energy is negative for the HYD path. Therefore, higher temperatures lead to the DDO path becoming the dominant path to toluene, whereas the HYD path, followed by fast equilibration to toluene, is less dominant, owing to the inhibition of the initial hydrogenation of m-cresol.
Synthesis, reactivity, and catalytic application of a nickel pincer hydride complex
Breitenfeld, Jan,Scopelliti, Rosario,Hu, Xile
experimental part, p. 2128 - 2136 (2012/06/01)
The nickel(II) hydride complex [(MeN2N)Ni-H] (2) was synthesized by the reaction of [(MeN2N)Ni-OMe] (6) with Ph2SiH2 and was characterized by NMR and IR spectroscopy as well as X-ray crystallography. 2 was unstable in solution, and it decomposed via two reaction pathways. The first pathway was intramolecular N-H reductive elimination to give MeN2NH and nickel particles. The second pathway was intermolecular, with H2, nickel particles, and a five-coordinate Ni(II) complex [(MeN2N)2Ni] (8) as the products. 2 reacted with acetone and ethylene, forming [( MeN2N)Ni-OiPr] (9) and [(MeN 2N)Ni-Et] (10), respectively. 2 also reacted with alkyl halides, yielding nickel halide complexes and alkanes. The reduction of alkyl halides was rendered catalytically, using [(MeN2N)Ni-Cl] (1) as catalyst, NaOiPr or NaOMe as base, and Ph2SiH2 or Me(EtO)2SiH as the hydride source. The catalysis appears to operate via a radical mechanism.
