- LA PHOTOLYSE DES ACIDES ET DES ESTERS
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Irradiation of saturated acids or esters below 220 nm leads to a Norrish-II cleavage or an 1,2-elimination in preparatively useful yields; this is illustrated by several efficient degradations, including that of the side-chain of bile acids.
- Wolff, Genevieve,Ourisson, Guy
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- Linear long-chain α-olefins from hydrodeoxygenation of methyl palmitate over copper phyllosilicate catalysts
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Copper phyllosilicate (CuPS) was used as a bifunctional catalyst for hydrodeoxygenation of methyl palmitate (MP) to produce long-chain α-olefins without the loss of carbon backbone. The CuPS catalysts were prepared by ammonia evaporation-hydrothermal method. The crystal structure, surface area, reducibility, Cu dispersion, Cu particle size and acidity of the catalysts were examined by XRD, BET, H2-TPR, TEM, NH3-TPD and Py-IR. The existence of Cu2+ species (octahedral (Oh)/square planar (Sq)), Cu+ and Cu0 upon calcination/reduction was investigated by in situ TR-XANES. The Cu dispersion was related to the Cu+ fraction in CuPS, while Br?nsted acid sites (BAS) depends on Cu0 particles. The MP conversion to 1-hexadecene proceeds via hydrogenation-dehydration promoted by the synergy of Cu0 surface and Br?nsted acid sites at the interface. The α-olefin selectivity depends on a balance between Cu+ and Cu loading. The 20CuPS possessing 10% Cu+ fraction, provides a high conversion of 72% with 45% α-olefin selectivity.
- Choojun, Kittisak,Huang, Ai-Lin,Lin, Yu-Chuan,Poo-arporn, Yingyot,Prasanseang, Warot,Sooknoi, Tawan
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- Norrish type II reactions of acyl azolium salts
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The photochemical reactivity of acyl azolium salts derived from aliphatic carboxylic acids has been investigated. These species, which serve as models for intermediates generated in N-heterocyclic carbene (NHC) organocatalysis, undergo Norrish type II elimination reactions under irradiation with UVA light in analogy to structurally related aromatic ketones. Moreover, efficient Norrish-Yang cyclization was observed from an adamantyl-substituted derivative. These results further demonstrate the ability of NHCs to influence the absorption properties and photochemical reactivity of carbonyl groups during a catalytic cycle.
- Hopkinson, Matthew N.,Mavroskoufis, Andreas,Rieck, Arielle
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- Ni-catalyzed reductive decyanation of nitriles with ethanol as the reductant
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A nickel-catalyzed reductive decyanation of aromatic nitriles has been developed, in which the readily available and abundant ethanol was applied as the hydride donor. Various functional groups on the aromatic rings, such as alkoxyl, amino, imino and amide, were compatible in this catalytic protocol. Heteroaryl, benzylic and alkenyl nitriles were also tolerated. Mechanistic investigation indicated that ethanol provided hydride efficientlyviaβ-hydride elimination in this reductive decyanation.
- Wu, Ke,Ling, Yichen,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu,Jin, Liqun,Hu, Xinquan
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supporting information
p. 2273 - 2276
(2021/03/09)
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- Surfactant-Free Synthesis of Ultrafine Pt Nanoparticles on MoS2Nanosheets as Bifunctional Catalysts for the Hydrodeoxygenation of Bio-Oil
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Hydrodeoxygenation (HDO) of bio-oil is a crucial step for improving the bio-fuel quality, but developing highly dispersed Pt-based catalysts with high selectivity for target alkanes remains a great challenge. This study presents a fast surfactant-free method to prepare the MoS2-supported Pt catalyst for HDO. Ultrafine Pt nanoparticles with sizes of 5 nm can be readily grown on chemically exfoliated MoS2 nanosheets (NSs) via the direct microwave-assisted thermal reduction. The obtained Pt NPs/MoS2 composites show excellent catalytic performance in the conversion of palmitic acid, and the best selectivity (also the yield) of hexadecane and pentadecane is 80.56 and 19.43%, respectively.
- Fan, Xiaobin,Li, Yang,Liang, Junmei,Lin, Qianqian,Peng, Wenchao,Xu, Danyun,Zhang, Fengbao,Zhang, Qicheng
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p. 14710 - 14716
(2020/12/23)
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- A hydroxylamine probe for profiling: S-acylated fatty acids on proteins
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Reversible S-palmitoylation is a key regulatory mechanism of protein function and localization. There is increasing evidence that S-acylation is not restricted to palmitate but it includes shorter, longer, and unsaturated fatty acids. However, the diversity of this protein modification has not been fully explored. Herein, we report a chemical probe that combined with MS-based analysis allows the rapid detection and quantification of fatty acids linked to proteins. We have used this approach to profile the S-acylome and to show that the oncogene N-Ras is heterogeneously acylated with palmitate and palmitoleate. Studies on protein distribution in membrane subdomains with semisynthetic proteins revealed that unsaturated N-Ras presents an increased tendency toward clustering and higher insertion kinetic rate constants.
- Schulte-Zweckel, Janine,Dwivedi, Mridula,Brockmeyer, Andreas,Janning, Petra,Winter, Roland,Triola, Gemma
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p. 11183 - 11186
(2019/09/30)
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- Hexadecane Conversion on an Alumina–Nickel Catalyst
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Abstract: The conversion of hexadecane on a 4% Ni/Al2O3 catalyst in a temperature range of 20–300°C was studied using IR spectroscopy and catalytic methods. It was found that the dehydrogenation of hexadecane occurred at 20–100°C with the subsequent formation of aromatic products, but the rates of these processes were very low. As the reaction temperature was increased to 200°C, the 4% Ni/Al2O3 catalyst exhibited a maximum activity and high selectivity for the formation of 1-hexadecene, and aromatic compounds and cracking products were present in the reaction products. As the reaction temperature was further increased, the catalytic activity significantly decreased. This was due to the fact that polyaromatic deposits gradually accumulated on the catalyst surface in a temperature range of 200–300°C.
- Chesnokov,Chichkan,Paukshtis,Chesalov, Yu. A.,Krasnov
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p. 439 - 445
(2019/09/04)
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- Selective Catalytic Hydrogenolysis of Carbon-Carbon σ Bonds in Primary Aliphatic Alcohols over Supported Metals
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The selective scission of chemical bonds is always of great significance in organic chemistry. The cleavage of strong carbon-carbon σ bonds in the unstrained systems remains challenging. Here, we report the selective hydrogenolysis of carbon-carbon σ bonds in primary aliphatic alcohols catalyzed by supported metals under relatively mild conditions. In the case of 1-hexadecanol hydrogenolysis over Ru/TiO2 as a model reaction system, the selective scission of carbon-carbon bonds over carbon-oxygen bonds is observed, resulting in n-pentadecane as the dominant product with a small quantity of n-hexadecane. Theoretical calculations reveal that the 1-hexadecanol hydrogenolysis on flat Ru (0001) undergoes two parallel pathways: i.e. carbon-carbon bond scission to produce n-pentadecane and carbon-oxygen bond scission to produce n-hexadecane. The removal of adsorbed CO on a flat Ru (0001) surface is a crucial step for the 1-hexadecanol hydrogenolysis. It contributes to the largest energy barrier in n-pentadecane production and also retards the rate for n-hexadecane production by covering the active Ru (0001) surface. The knowledge presented in this work has significance not just for a fundamental understanding of strong carbon-carbon σ bond scission but also for practical biomass conversion to fuels and chemical feedstocks.
- Di, Lu,Yao, Sikai,Li, Mengru,Wu, Guangjun,Dai, Weili,Wang, Guichang,Li, Landong,Guan, Naijia
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p. 7199 - 7207
(2015/12/11)
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- Photobiocatalytic decarboxylation for olefin synthesis
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Here, we describe the combination of OleTJE with a light-driven in situ H2O2-generation system for the selective and quantitative conversion of fatty acids into terminal alkenes. The photobiocatalytic system shows clear advantages regarding enzyme activity and yield, resulting in a simple and efficient system for fatty acid decarboxylation.
- Zachos, Ioannis,Ga?meyer, Sarah Katharina,Bauer, Daniel,Sieber, Volker,Hollmann, Frank,Kourist, Robert
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supporting information
p. 1918 - 1921
(2015/02/05)
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- Photon can tremendously accelerate the alkyl iodides' elimination in water
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Elimination of the alkyl halides in water is very difficult due to the heterogeneous nature and the limitation of base strength. We discovered that ultra-violet (UV) light can enhance the elimination rate of alkyl iodides, including primary, secondary, and tertiary iodides in water dramatically for the first time. We propose a tandem radical-carbocation reaction mechanism to rationalize this special property of alkyl iodides.
- Liu, Wenbo,Li, Chao-Jun
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supporting information
p. 1699 - 1702
(2015/03/14)
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- Investigation of hydrocarbon generation mechanism by polarizing the carboxy-group of fatty acid salt with microwave radiation
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Triglycerides can be converted to renewable hydrocarbons fuel which can be used as engine fuels by alkali pyrolysis decarboxylation and cracking processes. The purpose of present study was to explore decarboxylation mechanism of fatty acid salt with microwave radiation. Sodium stearate, potassium stearate, sodium oleate and sodium laurate was chosen as a model compound. The carboxy-terminal of this dipolar molecule was further polarized with microwave radiation. The Lorentz force of ions of dipolar molecules were moved in accordance with the way of electromagnetic waves, contribute to the formation of carbanion, which effectively promote the decarboxylation reaction. Moreover, the polarity of carboxy-terminal was stronger, more easily decarboxylation. The surface of glycerol formed a High-Temperature Locus in microwave radiation reaction system, facilitate the decarboxylation processe, in adition to played a role as the hydrogen donor for this high dielectric value compound. C8-C20 n-alkanes and n-alk-1-enes were arranged regular in liquid products. It proved the feasibility to derive renewable hydrocarbon fuel from sodium salt of fatty acids by microwave pyrolysis.
- Wang,Liu,Ruan,Wen,Wan,Zhang
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p. 369 - 375
(2014/06/09)
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- Carbon nanofibers supported molybdenum carbide catalysts for hydrodeoxygenation of vegetable oils
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Carbon nanofiber-supported molybdenum carbide catalysts (Mo 2C/CNF) with different loadings were prepared by the carbothermal hydrogen reduction method. Characterizations with Raman, XRD, N2-TGA, SEM, TEM and HAADF-STEM confirmed that Mo2C nanoparticles were successfully supported on the carbon nanofibers. The optimal reaction conditions with model compounds on Mo2C/CNF had a conversion of 98.03% and yield of 95.26%. It is interesting to note that a low evaporation rate positions the Mo2C nanoparticles on the outside of the CNF due to the capillary effect and the Mo2C nanoparticles on the outside of the CNFs showed high catalytic activity compared to ones on the inside of the CNFs. The Mo2C/CNF catalyst was recycled 5 times without any apparent loss of catalytic activity. Catalytic performances of Mo2C/CNF, Mo 2C/AC (activated carbon) and Mo2C/CNT (multi-walled carbon nanotubes) were examined using methyl palmitate and maize oil. The results showed that molybdenum carbide could be a potential substitute for noble metals in transformation of vegetable oils.
- Qin, Yu,Chen, Ping,Duan, Jinzhao,Han, Junxing,Lou, Hui,Zheng, Xiaoming,Hong, Haiping
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p. 17485 - 17491
(2013/09/24)
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- Copper-catalyzed highly selective semihydrogenation of non-polar carbon-carbon multiple bonds using a silane and an alcohol
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A copper catalyst bearing a suitable Xantphos derivative or NHC ligand was found to be highly efficient for the selective semihydrogenation of non-polar unsaturated compounds using a mixture of a silane and an alcohol as reducing agent. The catalytic system was useful for the selective semihydrogenation of internal alkynes to (Z)-alkenes with suppression of overreduction to the corresponding alkanes. Furthermore, semihydrogenations of terminal alkyne, 1,2-diene, 1,3-diene, 1,3-enyne and 1,3-diyne systems were also achieved selectively. Copyright
- Semba, Kazuhiko,Fujihara, Tetsuaki,Xu, Tinghua,Terao, Jun,Tsuji, Yasushi
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supporting information; experimental part
p. 1542 - 1550
(2012/08/08)
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- Aminophosphine-based chromium catalysts for selective ethylene tetramerization
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Chromium complexes of three new ligands, Ph2PN(Me)(CH 2)2-X [X = NMe2(PNN); PPh2 (PNP); Py (PNPy)], have been examined vis-a-vis their ability to promote ethylene tetramerization, (PNN)CrCl3(L) [L = THF (1); CH3CN (2)], (PNPy)CrCl3(L) [L = THF (3); CH3CN (4)], and (PNP)CrCl3(THF) (5). In the case of 2 and 4, it was possible to grow crystals suitable for X-ray diffraction. The reaction of 3 with Et3Al afforded the dinuclear [(HN(Me)(CH2)2Py)CrCl 2Et]2 (6) containing a trivalent chromium connected to an Et group. During the alkylation though, the ligand has been fragmented with removal of the side arm and protonation of the N atom of the remaining NP residue. All the complexes have been tested for ethylene oligomerization activity. Complex 1 displayed the highest selectivity for 1-octene, upon activation with DMAO in MeCy. Contrary to expectations, complex 6 is not a self-activating catalyst.
- Shaikh, Yacoob,Gurnham, Joanna,Albahily, Khalid,Gambarotta, Sandro,Korobkov, Ilia
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p. 7427 - 7433,7
(2020/10/15)
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- Fe5C2 nanoparticles: A facile bromide-induced synthesis and as an active phase for Fischer-Tropsch synthesis
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Iron carbide nanoparticles have long been considered to have great potential in new energy conversion, nanomagnets, and nanomedicines. However, the conventional relatively harsh synthetic conditions of iron carbide hindered its wide applications. In this
- Yang, Ce,Hou, Yanglong,Zhao, Huabo,Ma, Ding
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p. 15814 - 15821,8
(2020/08/24)
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- Photochemical method for producing hydrocarbons
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The present invention relates to a method of using radiation and (in one embodiment) solar energy and UV radiation to convert natural products, for example derivatives of vegetable oils, to lower molecular weight hydrocarbons. The invention further relates to a process whereby these hydrocarbons can be converted to vinyl monomers and used in the formation of plastics, solvents, fuels and the like.
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Page/Page column 9
(2012/02/14)
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- Iron-catalyzed decarbonylation reaction of aliphatic carboxylic acids leading to α-olefins
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The catalytic decarbonylation reaction of aliphatic carboxylic acids can be carried out in the presence of an iron complex, and it proceeds smoothly to give α-olefins with high selectivity. The Royal Society of Chemistry 2012.
- Maetani, Shinji,Fukuyama, Takahide,Suzuki, Nobuyoshi,Ishihara, Daisuke,Ryu, Ilhyong
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scheme or table
p. 2552 - 2554
(2012/03/26)
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- Molybdenum carbide-catalyzed conversion of renewable oils into diesel-like hydrocarbons
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In the paper, we report for the first time that the conversion of renewable oils into diesel-like hydrocarbon mixtures can be realized on molybdenum carbides with high activity and selectivity. The molybdenum carbide catalyst exhibited much better resistance to leaching than noble metals and could be reused consecutively for sixteen times without deactivation. Mechanism investigations indicated that molybdenum carbide and palladium showed different reaction selectivities and it was speculated that the level of difficulty in acyl-to-alkyl rearrangement of surface acyl intermediates on molybdenum carbide and palladium resulted in the different product selectivity. Copyright
- Han, Junxing,Duan, Jinzhao,Chen, Ping,Lou, Hui,Zheng, Xiaoming
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experimental part
p. 2577 - 2583
(2011/12/01)
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- Highly active ethylene oligomerization catalysts
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Reaction of RN(H)PBr(Ph)2N(H)R [R = t-Bu, i-Pr, Ph] with two equivalents of n-BuLi followed by reaction with CrCl2(THF) 2 afforded the divalent chromium complexes [(t-Bu)NP(Ph) 2N(t-Bu)]Cr(μ2-Cl)2Li(THF)2 (1), [(i-Pr)NP(Ph)2N(i-Pr)]Cr(μ2-Cl)2Li(THF) 2 (2), and [{[(Ph)NP(Ph)2N(Ph)]Cr}2(μ 2-Cl)3][Li(DME)3] (3). The trivalent analogue of 1, {[(t-Bu)NP(Ph)2N(t-Bu)]Cr(μ2-Cl) 3(μ3-Cl)2}{Li (THF)2} (4), was obtained in a similar manner via treatment of the double deprotonated ligand with CrCl3(THF)3. Both reactions of the divalent1 or trivalent4 with AlMe3 yielded the trivalent and cationic complex {[(t-Bu)NP(Ph)2N(t-Bu)]2Cr}{(Me3Al) 2Cl}?toluene (5). Upon activation with MAO, 1-3 produced unprecedented and potentially useful catalytic systems for nonselective ethylene oligomerization devoid of polymer. Divalent chromium is clearly the species responsible for the catalytic behavior, ruling out that nonselective oligomerization proceeds via a redox metallacycle mechanism. The absence of polymer in combination with the record activity makes 1 competitive with the best performing industrially used systems.
- Albahily, Khalid,Licciulli, Sebastiano,Gambarotta, Sandro,Korobkov, Ilia,Chevalier, Reynald,Schuhen, Kathrine,Duchateau, Robbert
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experimental part
p. 3346 - 3352
(2011/09/12)
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- Ethylene oligomerization promoted by a silylated-SNS chromium system
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The ethylene trimerization SNS ligand has been modified by replacing the methylene carbons flanking the nitrogen atom with dimethyl silyl groups. Three ligands, CySCH2Si(CH3)2N(H)Si(CH 3)2CH2SCy (a), (t-Bu)SCH2Si(CH 3)2N(H)Si(CH3)2CH2S(t-Bu) (b), and PhSCH2Si(CH3)2N(H)Si(CH 3)2CH2SPh (c), have been prepared. Ligand a in either protonated or deprotonated forms was reacted with CrCl 3(THF)3 to afford the corresponding monomeric [CySCH 2Si(CH3)2N(H)Si(CH3) 2CH2SCy]CrCl3 (1a) or dimeric {[CySCH 2Si(CH3)2NSi(CH3)2CH 2SCy]CrCl(μ-Cl)}2 (2a). One-pot reaction of a in the presence of Et2AlCl with either Cr(III) or Cr(II) chlorides afforded in either case the divalent {[CySCH2Si(CH3) 2N(H)Si(CH3)2CH2SCy]Cr{(μ-Cl) Al(CH2CH3)2Cl}2 (3a). To deprotonate the N-H function of the Si-SNS ligand, n-BuLi was used for the purpose of preparing the divalent chromium analogue. The reaction afforded in the case of both a and b the two nearly isostructural divalent complexes {[CySCH 2Si(CH3)2NSi(CH3)2CH 2SCy]Cr(μ-Cl)}2 (4a) and {[(t-Bu)SCH 2Si(CH3)2NSi(CH3)2CH 2S(t-Bu)]Cr(μ-Cl)}2 (4b) in crystalline form. To further clarify the interaction of 4 with aluminate species, we have carried out in situ complexation in the presence of either AlCl3 or AlMe 3 and using divalent instead of trivalent chromium salts. In the cases of ligands a and c and AlCl3, two isostructural complexes, {[CySCH2Si(CH3)2N(H)Si(CH3) 2CH2SCy]Cr{(μ-Cl)AlCl3}2 (5a) and {[PhSCH2Si(CH3)2N(H)Si(CH3) 2CH2SPh]C{(μ-Cl)AlCl3}2 (5c), have been obtained. The reaction with AlMe3 afforded {[CySCH 2Si(CH3)2N(Al(CH3) 2-μ-Cl)Si(CH3)2CH2SCy]Cr{(μ- Cl)Al(CH3)3} (6a). Its structure was informative, showing a possible catalyst deactivation pathway. To better evaluate the role of the N-H function, we have also methylated ligand a at the N atom. The complexation to chromium was successful only in the presence of Me2AlCl and if a divalent chromium precursor was used. The reaction afforded the catalytically inactive divalent {[CySCH2Si(CH3)2N(CH 3)Si(CH3)2CH2SCy]Cr(μ-Cl)} 2{(Al(CH3)2Cl)2)(μ-Cl)} 2 (7d). Most of these species showed good catalytic activity upon activation but produced only statistical distributions of oligomers.
- Albahily, Khalid,Gambarotta, Sandro,Duchateau, Robbert
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experimental part
p. 4655 - 4664
(2011/11/07)
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- Efficient iridium-catalyzed decarbonylation reaction of aliphatic carboxylic acids leading to internal or terminal alkenes
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Vaska's complex, IrCl(CO)(PPh3)2, when combined with KI as an additive, served as an excellent catalyst for the decarbonylation of long-chain aliphatic carboxylic acids to give internal alkenes with high selectivity. On combination with KI and Ac2O as additives under controlled temperatures, decarbonylation proceeded to give terminal alkenes with high selectivity.
- Maetani, Shinji,Fukuyama, Takahide,Suzuki, Nobuyoshi,Ishihara, Daisuke,Ryu, Ilhyong
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experimental part
p. 1389 - 1394
(2011/04/25)
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- Glassy carbon modified by a silver-palladium alloy: cheap and convenient cathodes for the selective reductive homocoupling of alkyl iodides
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Micrometer-thick layers of silver-palladium alloy were elaborated in order to modify the surface of glassy carbon electrodes. Such a surface modification can be readily achieved via a preliminary silver galvanostatic deposit onto carbon followed by a 'palladization' step, thanks to a simple immersion in acidic PdII-based solutions producing a displacement reaction. The as-prepared metallic interfaces exhibit outstanding catalytic capabilities especially in the cleavage of carbon-halogen bonds while being chemically/electrochemically quite stable and relatively inexpensive. More specifically, the use of such glassy carbon/Ag-Pd electrodes in dimethylformamide (DMF) containing tetraalkylammonium salts (TAA+X-) makes the one-electron reductions of primary alkyl iodides possible; this reduction leads to the formation of homodimers in high yields. Formation of a free radical as transient resulted from the homocoupling reaction.
- Poizot, Philippe,Jouikov, Viatcheslav,Simonet, Jacques
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body text
p. 822 - 824
(2009/05/07)
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- Process for the manufacture of base oil
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A feedstock originating from renewable sources is converted to branched and saturated hydrocarbons without heteroatoms in the base oils distillation range by converting the fatty acids to olefins, which are subsequently oligomerised.
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Page/Page column 8
(2008/06/13)
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- Iron-catalyzed cross-coupling of alkyl halides with alkenyl Grignard reagents
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(Chemical Equation Presented) Cheap and safe: An iron-catalyzed cross-coupling reaction between alkyl halides and alkenyl Grignard reagents is described. This C-C bond coupling reaction is promoted by the cheap and nontoxic FeCl3 and displays good tolerance against various functional groups.
- Guerinot, Amandine,Reymond, Sebastien,Cossy, Janine
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p. 6521 - 6524
(2008/09/16)
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- An unprecedented α-olefin distribution arising from a homogeneous ethylene oligomerization catalyst
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Treatment of the bis(benzimidazolyl)amine chromium complex 2 with ethylene in the presence of MAO affords an exceptionally active oligomerization catalyst and an unprecedented distribution of 1-olefin products in which the C4n series is much more abundant than the C4n+2 series. Deuterium labeling studies are consistent with a metallacyclic chain growth mechanism in which the unusual product distribution arises from the interplay of two sites. Copyright
- Tomov, Atanas K.,Chirinos, Juan J.,Long, Richard J.,Gibson, Vernon C.,Elsegood, Mark R. J.
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p. 7704 - 7705
(2007/10/03)
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- Cobalt-catalyzed dimerization of α-olefins to give linear α-olefin products
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[Cp*P(OMe)3CoCH2CH3]+ [BarF]-, generated by the addition of HBArF to Cp*P(OMe)3Co(ethene), catalyzes the oligomerization of 1-hexene to give dimers and trimers. When a deficit of the acid is used, linear α-olefin dimers are produced at the expense of trimeric products: e.g., 1-butene, 1-hexene, and 1-octene give 1-octene, 1-dodecene, and 1-hexadecene, respectively. Copyright
- Broene, Richard D.,Brookhart, Maurice,Lamanna, William M.,Volpe Jr., Anthony F.
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p. 17194 - 17195
(2007/10/03)
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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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- Synthesis, characterisation and catalytic of Pd(II) and Ni(II) complexes with new cyclic α-diphenylphosphino-ketoimines. Crystal structure of 2,6-diisopropyl-N-(2-diphenylphosphino-cyclopentylidene)aniline and of 2,6-diisopropyl-N-(2-diphenylphosphino-cyclohexylidene)aniline
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New cyclic α-diphenylphosphino-ketoimines have been synthesised by deprotonation of the corresponding imine and subsequent reaction with chlorodiphenylphosphine. The crystal structures of two of these compounds containing a cyclopentylidene and cyclohexylidene backbone are discussed. Reaction of these bidentate phosphorus-nitrogen (P∧N) ligands with (cod)Pd(CH3)Cl leads to neutral complexes of the general formula (P∧N)Pd(CH3)Cl which have been reacted with AgSbF6 to yield cationic complexes of formula [(P∧N)Pd(CH3)(NCCH3)]SbF6. Reaction of these ligands with (1,2-dimethoxyethane)NiBr2 yields neutral nickel(II) complexes that have been characterised by IR and elemental analysis. Cationic Pd(II) complexes as well as MAO-activated neutral nickel(II) complexes have been used as ethylene oligomerisation catalysts. The cationic palladium(II) complexes show a marked pressure dependence of TOF, with α-olefin fraction and Schulz-Flory α-values explainable in the light of the accepted mechanism for analogous complexes. By increasing the steric bulkiness of the substituent on the imine, or by using ligands with cyclohexylidene or cycloheptylidene backbone instead of cyclopentylidene, a drop in catalytic activity is observed. Nickel(II) complexes of the title ligands activated with MAO permit to confirm the latter conclusions. In comparison with palladium their use brings to comparable linearities but higher oligomerisation grades as well as α-olefin fraction. Cationic palladium(II) complexes are also active in the propene and 1-butene oligomerisation.
- Keim, Wilhelm,Killat, Stefan,Nobile, Cosimo F,Suranna, Gian Paolo,Englert, Ulli,Wang, Ruimin,Mecking, Stefan,Schr?der, Dirk Lucas
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p. 150 - 171
(2007/10/03)
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- Mammalian exocrine secretions. XVII: chemical characterization of preorbital secretion of male suni, Neotragus moschatus.
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Gas chromatographic and gas chromatographic-mass spectrometric techniques were employed to identify 83 compounds, including alkanes, alkenes, aldehydes, 2-methylalkanes, carboxylic acids, 1-alkyl formates and alken-1-yl formates, benzoic acid, and cholest
- Stander,Burger,Le, Roux M
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- Polymers and surfactants on the basis of renewable resources
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A new strategy for the preparation of different polymers and special surfactants was developed. First, unsaturated fatty acid methyl esters obtained from plant oils were converted to terminally unsaturated esters and α-olefins by metathesis with ethylene using heterogeneous rhenium or homogeneous ruthenium catalysts. These esters were directly copolymerized with ethylene by an insertion-type palladium-catalyzed polymerization to functionalized polyolefins. Polyesters were synthesized by metathetical dimerization of ω-unsaturated esters and subsequent polycondensation of the produced internally unsaturated dicarboxylic esters or by acidic transesterification with petrochemical diols and additional acyclic diene metathesis polymerization, ω-epoxy fatty acid methyl esters, achieved by a new method of chemo-enzymatic epoxidation, were converted into polyethers with comb-structure catalyzed by aluminoxanes on the one hand and into sugar surfactants by nucleophilic ring-opening with amino carbohydrates on the other hand.
- Warwel, Siegfried,Bruese, Falk,Demes, Christoph,Kunz, Michael,Klaas, Mark Ruesch gen
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- Reduction of fatty acid methyl esters to fatty alcohols to improve volatility for isotopic analysis without extraneous carbon.
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Carbon in derivatization groups cannot be distinguished from analyte carbon by chromatography-based high-precision compound-specific or position-specific isotope analysis. We report the reduction of fatty acid methyl esters to fatty alcohols to facilitate high-quality chromatographic separation, without addition of extraneous carbon, with subsequent high-precision position-specific isotope analysis. Methyl palmitate is quantitatively reduced to 1-hexadecanol by LiAlH4 in a one-step reaction. Gas-phase pyrolysis of 1-hexadecanol results in a series of monounsaturated alcohols and alpha-olefins analogous to fragmentation found for methyl palmitate, as well as an additional peak corresponding to the pyrolytic dehydration product, 1-hexadecene. Carbon isotope analysis of the fragments yielded precision of SD (delta 13C) 0.4/1000. Results of position-specific analysis of very low enrichment [1-13C]-1-hexadecanol (delta 13C = -4.00/1000) showed no evidence of scrambling of the C1 position, and isotope ratios in accord with expectations. The pyrolysis product 1-hexadecene was isotopically enriched relative to 1-hexadecanol, which may cause minor depletion of other pyrolysis products that can be taken into account by routine calibration. The procedure is general and can be extended to compound-specific and position-specific analysis of moderate molecular weight, low-volatility analytes containing acid groups that would otherwise be blocked with methyl, ethyl, acetyl, or trimethyl silyl groups containing extraneous carbon.
- Corso,Lewis,Brenna
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p. 3752 - 3756
(2007/10/03)
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- Observations on the generation of organozinc carbenoids from acetals and ketals
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The use of acetals and ketals as direct precursors for organozinc carbenoid chemistry is illustrated by their direct conversion to alkenes in a one pot operation. Aryl acetals can also be used as precursors for the cyclopropanation of cyclohexene.
- Motherwell, William B.,O'Mahony, Donogh J.R.,Popkin, Matthew E.
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p. 5285 - 5288
(2007/10/03)
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- A new stereoselective synthesis of phosphiranes
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The synthesis of phosphiranes from primary phosphines and diol ditosylates was found to be stereoselective, and chiral phosphiranes were prepared from optically pure diols. The four optical isomers of 1-mesityl-2,3-dimethylphosphirane, (2S,3S)-(+)-3, (2R,3R)-(-)-4, anti-cis-(meso)-5, and syn-cis-(meso)-6, were all synthesized from mesitylphosphine and the corresponding diol ditosylates. Compound 6 was unstable, but compounds 3, 4, and 5 were all isolated in pure form. Their structure assignments were based on the NMR coupling constants JP-H and JP-C. The phosphiranes were transformed into tungsten pentacarbonyl complexes. Tungsten tetracarbonyl-triphenylphosphine complexes (22, 23, 24) of compounds 3, 4, and 5 were synthesized in high yields by the reaction of the phosphiranes and W(CO)4(PPh3)(THF). The absolute stereochemistry of the phosphiranes 3, 4, and 5 was determined by X-ray crystal structure analysis of compounds 22, 23, and 24. Stereochemical effects on NMR coupling constants and mass spectra of the phosphiranes are discussed.
- Li, Xinhua,Robinson, Kerry D.,Gaspar, Peter P.
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p. 7702 - 7710
(2007/10/03)
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- Sulfur ylide vinylation of halides and mesylates
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One-carbon homologation of benzylic, allylic, propargylic and primary halides or mesylates with dimethylsulfonium methylide affords terminal olefins in good to excellent yields.
- Alcaraz,Harnett,Mioskowski,Martel,Le Gall,Shin, Dong-Soo,Falck
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p. 5453 - 5456
(2007/10/02)
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- Telluroxide Elimination by Oxidation of Alkyl Aryl Tellurides: Remarkable Effect of Added Triethylamine
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Treatment of various alkyl phenyl tellurides with 1-2 mol equiv. of m-chloroperbenzoic acid in diethyl ether in the presence of triethylamine at 25 deg C for 2 h affords the corresponding alkenes highly selectively in fair to good yields.From stereochemical studies using erythro- and threo-phenyl 3-phenylbutan-2-yl tellurides as substrates it was revealed that although Et3N partly faciliates E2 elimination of the telluroxide, the main reaction course is the telluroxide syn-elimination (Ei elimination).Without the addition of Et3N the elimination was quite slow in many cases, and in fact the compounds derived from the addition of m-chlorobenzoic acid to tetradecyl and cyclohexyl phenyl telluroxides were isolated, the pyrolysis (ca. 250 deg C) of which afforded tetradec-1-ene and cyclohexene, respectively.A 2-pyridyltelluro moiety was revealed for the first time to be a better leaving group than a phenyltelluro moiety in telluroxide elimination.
- Nishibayashi, Yoshiaki,Komatsu, Naoki,Ohe, Kouichi,Uemura, Sakae
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p. 1133 - 1138
(2007/10/02)
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- SYMMETRICAL AND UNSYMMETRICAL COUPLING OF ALKYL HALIDES MEDIATED BY GRIGNARD REACTION
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A simple method for extending the carbon chain via the coupling of alkyl or aryl halides has been developed.The versatility of this reaction has been demonstrated by symmetrical and unsymmetrical coupling of alkyl, alkenyl or alkynyl halides.
- Herendeen, Barbara L.,Bhatia, Suresh K.,Singh, Alok
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p. 2899 - 2908
(2007/10/02)
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- EASY AND EFFICIENT HETEROGENEOUS NUCLEOPHILIC FLUORINATION WITHOUT SOLVENT
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In the absence of solvent, either or were found to be effective and practical reagents for the fluorination of several organic halides under mild conditions.
- Bram, Georges,Loupy, Andre,Pigeon, Philippe
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p. 1661 - 1668
(2007/10/02)
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- Spiro[isoxazalidine-3,2'-tricyclo[3.3.1.13,7 ] decanes]
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The compounds are of the class of adamantanyl isoxazolidine derivatives useful as anti-inflammatory, antihypoxia, antimicrobial and anticonvulsant agents. Exempliary of a species of the compounds is 2 methyl-5-n-hexyl-spiro[isoxazolidin-3,2'-tricyclo[3.3.1.13,7 ] decane].
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- Photochemistry of ketones adsorbed on porous silica
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The Phetochemical reactions of several families of ketones adsorbed on various forms of silica have been investigated. The influence of surface coverage, silica average pore diameter, temperature, applied magnetic fields, and additives on the product distributions have been determined. The results are consistent with a model in which the silica surface consists of two major regions, one consisting of stronger binding sites (active silanol groups) and the other consisting of weaker binding sites (free silanol groups). The relative proportions of these two types of sites are related to the pore size of the silica, smaller pores correlating with a larger fraction of the stronger binding sites and larger pores correlating with a smaller fraction of the stronger binding sites. At low coverage, the initial location of a ketone in one of the two binding sites is an important factor in determining the product distributions. Some preliminary results are reported on the time resolved spectroscopy of ketones adsorbed on silica investigated by diffuse reflectance absorption spectrescopy.
- Turro, Nicholas J.
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p. 1589 - 1616
(2007/10/02)
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- LIQUID-CRYSTALLINE SOLVENTS AS MECHANISTIC PROBES. 23. NORRISH II REACTIONS OF 2- AND SYM-ALKANONES IN THE ISOTROPIC, SMECTIC B, AND CRYSTALLINE PHASES OF n-BUTYL STEARATE.
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n-Alkanones with the carbonyl group at the 2 or central positions (1 and 2, respectively) have been irradiated in the isotropic, smectic B, and two solid phases of n-butyl stearate (BS).The lengths of the ketones were varied from 11 to 31 carbons.The ratios of elimination/cyclization products and diastereomeric cyclobutanol products were measured for each as a function of temperature and BS phase.The effect of 1 and 2 on the phase transition temperatures of BS has been correlated with changes in the product ratios.The experiments demonstrate that a very sensitive cooperative relationship exists between the ease with which 1 and 2 fit into the ordered phases of BS and the degree to which the solvent matrices influence ketone photochemistry.The influence of solvent order on the product ratios is distinctly different for 1 and 2, and for the two product ratios from one ketone.
- Treanor, Richard L.,Weiss, Richard G.
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p. 1371 - 1392
(2007/10/02)
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- A Simple, Mild Elimination of Hydrogen Halide from Primary Alkyl Bromides and Iodides
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Addition of a solution of a primary alkyl bromide or iodide and 1,8-diazabicycloundec-7-ene in tetrahydrofuran (THF) to a solution prepared from dichlorobis(triphenylphosphine)nickel, triphenylphosphine, and n-butyl-lithium in THF results in an elimination at room temperature to give, in most cases, the terminal alkene.
- Jeropoulos, Sotiris,Smith, Edward H.
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p. 1621 - 1622
(2007/10/02)
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- Liquid-Crystalline Solvents as Mechanistic Probes. 20. Crystalline and Smectic B Solvent Control over the Selectivity of Photodimerization of n-Alkyl Cinnamates
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The photodimerizations of n-octadecyl, n-hexadecyl, and n-tetradecyl esters of trans-cinnamic acid have been investigated in the crystalline, smectic B, and isotropic phases of n-butyl stearate.A strong preference for head-to-tail dimerization is found in the ordered solvent phases.Dipole-dipole-induced interactions between cinnamates and solvent-mediated solute alignments are the factors that combine to control the regioselectivity of photodimerization.The ability of cinnamate esters to be incorporated into the ordered solvent phases is extremely dependent upon the length of the n-alkyl solute chains.However, ease of incorporation has little influence upon regioselectivity.
- Ramesh, Varadaray,Weiss, Richard G.
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p. 2535 - 2539
(2007/10/02)
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- A MILD AND EFFICIENT DEBROMINATION OF VICINAL DIBROMOALKANES WITH SODIUM TELLURIDE PREPAED FROM TELLURIUM AND RONGALITE
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Vicinal dibromoalkanes are debrominated to alkenes with remarkable ease by treatment with sodium telluride prepared from tellurium and Rongalite in aqueous alkaline medium.
- Suzuki, Hitomi,Inouye, Masahiko
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p. 225 - 228
(2007/10/02)
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- Catalytic Debromination of Vicinal Dibromides via Phase Transfer of Diaryltellurium Compounds
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Several vicinal dibromides were debrominated to olefins by potassium disulfite in the presence of catalytic amounts of bis(4-methoxyphenyl) telluride in a two phase system.
- Suzuki, Hitomi,Kondo, Akiko,Osuka, Atsuhiro
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p. 1335 - 1336
(2007/10/02)
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- Type II Photochemistry of Ketones in Liquid Crystalline Solvents. The Influence of Ordered Media on Biradical Dynamics
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The Norrish type II photochemistry of five alkylphenones, PhCO(CH2)nH (1a, n=4; 1b, n=10; 1c, n=17; 1d, n=19; 1e, n=21), 10-nonadecanone (2), and 2-undecanone (3) was studied in the isotopic, smetic, and solid phases of n-butyl stearate.The ratio of elimination-to-cyclization products for ketones 1c-e and 2 exhibits a strong phase dependence with a 7-8-fold increase in the smectic phase relative to the isotropic phase.The ratio of isomeric cyclobutanols from 2 shows a similar change.Further increases in the elimination-to-cyclization ratio are observed for 1d in the solid phase.The product ratios for ketones 1a, 1b, and 3 are the same in all the phase studied.Transient absorption studies on the intermediate 1,4-biradical produced from laser flash photolysis of 1d yield lifetimes of 64 +/- 5 and 70 +/- 5 ns in the isotopic and smectic phases, respectively.These results are explaned in terms of the structures of the various phases of n-butyl stearate and the accepted behavior of Norrish type II biradicals.
- Hrovat, David A.,Liu, Jerry H.,Turro, Nicholas J.,Weiss, Richard G.
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p. 7033 - 7037
(2007/10/02)
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- PHOTOCHEMISTRY OF N-ACYLAZOLES. VI). PHOTOREACTIVITIES OF 1-ACYL-1,2,4-TRIAZOLES AND OF 2-ACYLTETRAZOLES
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Contrary to the findings in the photolysis of N-acylimidazoles (2) irradiation of 1-acyl-1,2,4-triazoles afforded no photo-Fries product, but instead products formed via the corresponding acyl radicals and aldehydes.Photolysis of 2-acyltetrazoles gave in part the same products as those obtained from the irradiation of the corresponding acyl-triazoles as well as 2-alkyl-1,3,4-oxadiazoles.N-Acyltetrazoles didn't give any photo-Fries product neither.
- Murato, Kazuo,Yatsunami, Takashi,Iwasaki, Shigeo
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p. 588 - 605
(2007/10/02)
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- AN IMPROVED METHOD FOR OLEFIN SYNTHESIS USING PYRIDYLSELENO GROUP AS A LEAVING GROUP
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Alkyl pyridyl selenides are oxidized by 1.5 equiv. of 30percent H2O2 in THF to give olefins in good to excellent yields.The yields are always higher than the case where alkyl phenyl selenides are used under the same conditions.
- Toshimitsu, Akio,Owada, Hiroto,Uemura, Sakae,Okano, Masaya
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p. 5037 - 5038
(2007/10/02)
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