- A study of molybdenum catalysts in the polymerization of 2,5-didodecyl-1,4-dipropynylbenzene
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The reaction of 2,5-didodecyl-1,4-dipropynylbenzene with different molybdenum sources (Mo(CO)6, norbornadiene-Mo(CO)4, cyclooctadiene-Mo(CO)4, cycloheptatriene-Mo(CO)3, (PhCCPh)3Mo(CO), (acac)2MoO2/AlEt3) was investigated in the presence of 4-chlorophenol or 2-fluorophenol. Upon heating to 105-130°C, the formation of didodecyl-PPE resulted. The degree of polymerization of the PPE is dependent on the used phenol and to the utilized molybdenum precursor. The most active catalyst forms from (acac) 2MoO2, AlEt3 and 2-fluorophenol. This catalyst combination gives high molecular weight PPEs after 6 h at 105°C.
- Bly, Ruta K.,Dyke, Kristen M.,Bunz, Uwe H.F.
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Read Online
- Laser powered homogeneous pyrolysis of ethyne, propyne, and propadiene initiated by methyl radicals: Formation and degradation of hydrocarbons at 800-950 K
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Applying laser heating by fast vibrational-translational energy transfer in a quasi-wall-free reactor the pyrolysis of ethyne (C2H2), propyne (p-C3H4), and propadiene (a-C3H4) was studied experimentally at 0.13 bar in the medium temperature range of 800-950 K with respect to the degradation and formation of hydrocarbons. The radical/hydrocarbon chemistry was chemically induced via CH3 radicals produced by the fast thermal dissociation of di-tert-butyl-peroxide DTBP ((tert-C4H9O)2 → 2 CH3 + 2 CH3COCH3). Complete analysis of the product yields was achieved by means of GC-MS with special attention to isomeric product and benzene formation. The product distribution, the temperature dependence and the underlying reaction schemes were analyzed by kinetic models developed for high temperature alkane oxidation/pyrolysis and aromatic formation in premixed ethene and ethyne flames. The primary attack of the unsaturated hydrocarbons by CH3 radicals in the studied temperature range occurs via the addition to the double/triple bond and via hydrogen atom abstraction, leading to different classes of radicals. For the reaction system C2H2 + CH3 high yields of C6H6 with a marked negative temperature dependence were observed. A semi-quantitative description of the C6H6 yield was obtained by a reaction sequence of successive addition of C2H2 to the radicals C2H3 (from C2H2 + H) and C4H5, being consistent with recent discussed reaction networks. For the reaction systems p-C3H4 + CH3 and a-C3H4 + CH3 only qualitative agreement between measured and modelled product yields was found, pointing to a lack of reliable data of the reactions of p-C3H4/a-C3H4/C3H 3/H. Modified mechanisms are presented for the radical rich reaction systems C2H2 + CH3, p-C3H4 + CH3, and a-C3H4 + CH3 experimentally studied.
- Goos, Elke,Hippler, Horst,Hoyermann, Karlheinz,Juerges, Bettina
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Read Online
- Synthesis of 28-homobrassinosteroids modified in the 26-position
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28-Homobrassinosteroids modified in the 26-position were synthesized from 22-hydroxy-23-ensteroids using Claisen rearrangement and subsequent cis-hydroxylation of the resulting Δ22-derivative.
- Litvinovskaya,Raiman,Khripach
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Read Online
- Direct Evidence on the Mechanism of Methane Conversion under Non-oxidative Conditions over Iron-modified Silica: The Role of Propargyl Radicals Unveiled
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Radical-mediated gas-phase reactions play an important role in the conversion of methane under non-oxidative conditions into olefins and aromatics over iron-modified silica catalysts. Herein, we use operando photoelectron photoion coincidence spectroscopy to disentangle the elusive C2+ radical intermediates participating in the complex gas-phase reaction network. Our experiments pinpoint different C2-C5 radical species that allow for a stepwise growth of the hydrocarbon chains. Propargyl radicals (H2C?C≡C?H) are identified as essential precursors for the formation of aromatics, which then contribute to the formation of heavier hydrocarbon products via hydrogen abstraction–acetylene addition routes (HACA mechanism). These results provide comprehensive mechanistic insights that are relevant for the development of methane valorization processes.
- ?ot, Petr,Hemberger, Patrick,Pan, Zeyou,Paunovi?, Vladimir,Puente-Urbina, Allen,van Bokhoven, Jeroen Anton
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supporting information
p. 24002 - 24007
(2021/10/01)
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- Lanthanide-Catalyzed Reversible Alkynyl Exchange by Carbon–Carbon Single-Bond Cleavage Assisted by a Secondary Amino Group
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Lanthanide-catalyzed alkynyl exchange through C?C single-bond cleavage assisted by a secondary amino group is reported. A lanthanide amido complex is proposed as a key intermediate, which undergoes unprecedented reversible β-alkynyl elimination followed by alkynyl exchange and imine reinsertion. The in situ homo- and cross-dimerization of the liberated alkyne can serve as an additional driving force to shift the metathesis equilibrium to completion. This reaction is formally complementary to conventional alkyne metathesis and allows the selective transformation of internal propargylamines into those bearing different substituents on the alkyne terminus in moderate to excellent yields under operationally simple reaction conditions.
- Shao, Yinlin,Zhang, Fangjun,Zhang, Jie,Zhou, Xigeng
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supporting information
p. 11485 - 11489
(2016/10/24)
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- An acelylenically of a diene compound and/or method of manufacturing
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Provided is a novel method for producing a compound having acetylene bonds and/or a diene. The method for producing a compound having acetylene bonds and/or a diene is characterized in that at least one selected from the group consisting of ketone compound (I), ketone compound (II), aldehyde compound (III), aldehyde compound (IV), and aldehyde compound (V) is dehydrated in the presence of a catalyst wherein a carrier containing silica supports at least one selected from the group consisting of compounds containing group 1 metal elements, compounds containing group 2 metal elements, group 1 metal elements, and group 2 metal elements.
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Paragraph 0427; 0428; 0437-0445
(2017/03/28)
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- UV laser photodeposition of nanomagnetic soot from gaseous benzene and acetonitrile-benzene mixture
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Megawatt KrF laser gas-phase photolysis of benzene and acetonitrile-benzene mixture was studied by using mass spectroscopy-gas-chromatography and Fourier transform infrared spectroscopy for analyses of volatile products, and by Fourier transform infrared, Raman and X-ray photoelectron spectroscopy, electron microscopy and magnetization measurements for analyses of solid products deposited from the gas-phase. The results are consistent with carbonization of benzene and decomposition of non-absorbing acetonitrile in carbonizing benzene through collisions with excited benzene and/or its fragments. The solid products from benzene and acetonitrile-benzene mixture have large surface area and are characterized as nanomagnetic amorphous carbonaceous soot containing unsaturated C centers prone to oxidation. The nanosoot from acetonitrile-benzene mixture incorporates CN groups, confirms reactions of benzene fragments with CN radical and has a potential for modification by reactions at the CN bonds.
- Pola, Josef,Ouchi, Akihiko,Mary?ko,Vorlí?ek,?ubrt, Jan,Bakardjieva,Bastl, Zdeněk
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experimental part
p. 188 - 194
(2012/02/02)
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- Complete study of the pyrolysis and gasification of scrap tires in a pilot plant reactor
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The pyrolysis and gasification of tires was investigated in a pilot plant reactor provided with a system for condensation of semivolatile matter. The study comprised experiments at 450°, 750°, and 1000°C both in nitrogen and 10% oxygen atmospheres. In the gas phase, only methane and benzene yields increased with temperature until 1000°C. In the liquids, the main components were styrene, limonene, and isoprene. The solid fraction (including soot) increased with temperature. Zinc content of the char decreased with increasing temperature. Analysis of the surface area of the solids showed that the area was similar in all cases to that of a commercial carbon black. The higher surface of the soot with respect to the chars was observed. The results coincided with published findings, i.e., kinetic severity function values would produce 0.2% of methane at 450°C and 4.5% at 750°-1000°C.
- Conesa, Juan A.,Martin-Gullon,Font,Jauhiainen
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p. 3189 - 3194
(2008/12/21)
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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 of enamides from aldehydes and amides
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A range of double unsaturated amides (15, 19, and 21), obtained by cross-coupling reactions was reacted with aldehydes to hemiaminals. Heating the hemiaminals in the presence of Ac2O and pyridine affected clean conversion to the corresponding enamides, such as 42, 45, and 47. Alternatively, N,S-acetals were prepared which were oxidized to the sulfones. Treatment with base also gave the enamides, favoring the cis-isomer. However, this method is less general. Application of these methods led to the natural products lansiumamide-A (30_cis), lansiumamide-I (31) and lansiumamide-B (32).
- Bayer, Alexander,Maier, Martin E.
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p. 6665 - 6677
(2007/10/03)
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- Synthesis and pyrolytic and kinetic behaviour of β,δ′-dioxo-stabilised phosphorus ylides: Convenient preparation of γ,δ-alkynyl ketones and 2,3-functionalised butadienes
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Both ketone- and ester-stabilised phosphorus ylides undergo Michael addition to vinyl ketones to give the β,δ′-dioxo ylides 3 and 5, respectively, although in the latter case careful temperature control is required to avoid an undesired side-reaction. Under conditions of flash vacuum pyrolysis at 650 °C the ylides 3 generally undergo Ph3PO extrusion to afford the γ,δ-alkynyl ketones 14, although these are found to partly undergo a secondary fragmentation. In contrast, the ylides 5 react under the same conditions to give the synthetically useful 1,3-dienes 20 by way of cyclobutenes. Rate constants for the reaction of selected ylides 3 and 5 are reported. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).
- Aitken, R. Alan,Al-Awadi, Nouria A.,Balkovich, Mark E.,Bestmann, Hans Juergen,Clem, Oliver,Gibson, Scott,Gross, Andreas,Kumar, Ajith,Roeder, Thomas
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p. 840 - 847
(2007/10/03)
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- Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
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Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
- Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
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p. 402 - 415
(2007/10/03)
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- Kinetics of the Reactions of AHyl and Propargyl Radicals with CHb
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The allyl-methyl and propargyl-methyl cross-radical reactions were studied by laser photolysis/photoionization mass spectroscopy. Overall rate constants were obtained in direct real-time experiments in the temperature region 301-800 K and bath gas (helium
- Knyazev, Vadim D.,Slagle, Irene R.
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p. 3196 - 3204
(2007/10/03)
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- Kinetics and products of propargyl (C3H3) radical self-reactions and propargyl-methyl cross-combination reactions
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Propargyl and methyl radicals were produced through the 193-nm excimer laser photolysis of mixtures of C3H3Cl/He and CH3N2CH3/He, respectively. Gas chromatographic and mass spectrometric (GC/MS) product analyses were employed to characterize and quantify the major reaction products. The rate constants for propargyl radical self-reactions and propargyl-methyl cross-combination reactions were determined through kinetic modeling and comparative rate determination methods. The major products of the propargyl radical combination reaction, at room temperature and total pressure of about 6.7 kPa (50 Torr) consisted of three C6H6 isomers. The rate constant determination in the propargyl-methyl mixed radical system yielded a value of (4.0±0.4)×10-11 cm3 molecule-1 s-1 for propargyl radical combination reactions and a rate constant of (1.5±0.3)×10-10 cm3 molecule-1 s-1 for propargyl-methyl cross-combination reactions. The products of the methyl-propargyl cross-combination reactions were two isomers of C4H6, 1-butyne (about 60%) and 1,2-butadiene (about 40%).
- Fahr, Askar,Nayak, Akshaya
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p. 118 - 124
(2007/10/03)
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- Thermal decomposition of 2,5-dimethylfuran. Experimental results and computer modeling
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The thermal reactions of 2,5-dimethylfuran were studied behind reflected shock waves in a pressurized driver single pulse shock tube over the temperature range 1070-1370 K and overall densities of ～3 × 10-5 mol/ cm3. A large number of products resulting from unimolecular cleavage of the ring and consecutive free radical reactions were obtained under shock heating. A methyl group migration from C(2) to C(3) in the ring with the elimination of CO produces four isomers of C5H8 in unimolecular processes. An additional unimolecular process is the decomposition of 2,5-dimethylfuran to CH3CO and C4H5 which is an important initiator of free radical reactions. Ejection of a hydrogen atom from the methyl group in the molecule is another channel for initiation of free radical reactions in the system. The 2,5-dimethylfuryl radical, which is obtained in the process of H-atom ejection, decomposes in channels similar to those of 2,5-dimethylfuran to produce, among other products, C5H7, which is the precursor of cyclopentadiene. The major decomposition product found in the post shock mixtures is carbon monoxide. The rate constant of its overall formation is estimated as kCO = 1015.81exp(-75.1 × 103/RT) s-1 where R is expressed in units of cal/(K mol). Other products that were found in the postshock samples in decreasing order of abundance were C4H4, C2H2, and CH4 in roughly the same abundance, C2H4, C2H6, CH2=CH-CH=CH2, cyclopentadiene p-C3H4, and a-C3H4 and 2-methylfuran. Other isomers of C4H6, C5H6 and C5H8, and some additional products were found in very small quantities. The total decomposition of 2,5-dimethylfuran in terms of a first-order rate constant is given by: ktotal = 1016.22exp(-77.5 × 103/RT)s-1. An oxygen-carbon mass balance among the decomposition products is obtained. A reaction scheme composed of 50 species and some 180 elementary reactions accounts for the product distribution over the temperature range covered in this study. First-order Arrhenius rate parameters for the formation of the various reaction products are given, a reaction scheme is suggested, and results of computer simulation and sensitivity analysis are shown. Differences and similarities among the reactions of furan, 2-methylfuran, and 2,5-dimethylfuran are discussed.
- Lifshitz, Assa,Tamburu, Carmen,Shashua, Ronen
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p. 10655 - 10670
(2007/10/03)
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- Decomposition of 2-methylfuran. Experimental and modeling study
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The thermal reactions of 2-methylfuran were studied behind reflected shock waves in a pressurized driver single pulse shock tube over the temperature range 1100-1400 K and with overall densities of approx. 3 × 10-5 mol/cm3. A large number of products resulting from unimolecular cleavage of the ring and consecutive free radical reactions were obtained under shock heating. The unimolecular decomposition is initiated by two parallel channels: (1) 1,2-hydrogen atom migration from C(5) to C(4) and (2) a methyl group migration from C(2) to C(3) in the ring. Each channel is followed by two parallel modes of ring cleavage. In the first channel, breaking the O - C(2) and the C(4) - C(5) bonds in the ring yields CO and different isomers of C4H6, whereas breaking of the O - C(2) and the C(3) - C(4) bonds yields CH2CO and two isomers C3H4. In the second channel, breaking the O - C(5), and C(2) - C(3) bonds in the ring yields again CO and isomers of C4H6, whereas in the second mode O - C(5), C(2) - C(3), and C(3) - C(4) are broken to yield CO, C2H2, and C2H4. The four C4H6 isomers in decreasing order of abundance were 1,3-butadiene, 1-butyne, 1,2-butadiene, and 2-butyne. The major decomposition product is carbon monoxide. The rate constant for its overall formation is estimated to be kCO = 1015.88 exp(-78.3 × 103/RT) s-1, where R is expressed in units of cal/(K mol). Other products that were found in the postshock samples in decreasing order of abundance were C4H4, C2H2, CH4, p-C3H4, C2H6, C2H4, a-C3H4, C6H6, C4H4O, C3H6, and C4H2. The total decomposition of 2-methylfuran in terms of a first order rate constant is given by ktotal = 1014.78 exp(-71.8 × 103/RT) s-1. This rate and the production rate of carbon monoxide are slightly higher than the ones found in the decomposition of furan. An oxygen-carbon mass balance among the decomposition products was obtained. A reaction scheme composed of 36 species and some 100 elementary reactions accounts for the product distribution over the temperature range covered in this study. First order Arrhenius rate parameters for the formation of the various reaction products are given, a reaction scheme is suggested, and results of computer simulation and sensitivity analysis are shown. Differences and similarities in the reactions of furan and 2-methylfuran are discussed.
- Lifshitz,Tamburu,Shashua
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p. 1018 - 1029
(2007/10/03)
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- Thermal Isomerization and Decomposition of 1,2-Butadiene in Shock Waves
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1,2-Butadiene diluted with Ar was heated behind reflected shock waves over the temperature and the total density ranges of 1100 - 1600 K and 1.36*10-5 - 1.75*10-5 mol/cm3.The major products were 1,3-butadiene, 1-butyne, 2-butyne, vinylacetylene, diacetylene, allene, propyne, C2H6, C2H4, C2H2, CH4, and benzene, which were analyzed by gas-chromatography.The UV kinetic absorption spectroscopy at 230 nm showed that 1,2-butadiene rapidly isomerizes to 1,3-butadiene from the initial stage of the reaction above 1200 K.In order to interpret the formation of 1,3-butadiene, 1-butyne, and 2-butyne, it was necessary to include the parallel isomerizations of 1,2-butadiene to these isomers.The present data were successfully modeled with a 82 reaction mechanism.From the modeling, rate constant expressions were derived for the isomerization 1,2-butadiene = 1,3-butadiene to be k3 = 2.5*1013 exp(-63 kcal/RT) s-1 and for the decomposition 1,2-butadiene = C3H3 + CH3 to be k6 = 2.0*1015 exp(-75 kcal/RT) s-1, where the activation energies, 63 kcal/mol and 75 kcal/mol, were assumed.These rate constants are only applicable under the present experimental conditions, 1100 - 1600 K and 1.23 - 2.30 atm.
- Hidaka, Yoshiaki,Higashihara, Tetsuo,Ninomiya, Natsuhiko,Oki, Takashi,Kawano, Hiroyuki
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p. 331 - 342
(2007/10/02)
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- Flash Vacuum Pyrolysis of Stabilised Phosphorus Ylides. Part 1. Preparation of Aliphatic and Therminal Alkynes
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Thermal extrusion of Ph3PO from β-oxoalkylidenetriphenylphosphoranes 4 to give the alkynes 5, which under conventional pyrolysis conditions is restricted to cases in which R1 is an electron withdrawing group, has been successfully achieved for R1=H or alkyl by using FVP.The method allows convenient construction of multigram quantities of the alkynes 5 from alkyl halides 1 and allows convenient construction of multigram quantities of the alkynes 5 from alkyl halides 1 and acid chlorides 3 in three steps with good overall yields.Under the conditions used the ylides with R2 = cyclobutyl also undergo less of ethene to provide convenient access to the vinylalkynes 6.
- Aitken, R. Alan,Atherton, J. Ian
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p. 1281 - 1284
(2007/10/02)
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- Kinetics of the Reaction of CH2(a1A1) with CH3C2H, HCN, CO2, N2O and COS
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The reactions of CH2(a1A1) with CH3C2H, HCN, CO2, N2O and COS are investigated at room temperature.CH2(a1A1) is generated by pulsed laser photolysis of CH2CO.Overall removal rate constants are derived from concentration profiles under first order reaction conditions using direct, time resolved LIF detection of CH2(a1A1).The second order rate constants are found in units of 1E13 cm2/mol s to be 24, 18, 2.0, 3.8 and 20, respectively. - The contribution of physical quenching to the removal of CH2(a1A1) are determined by monitoring directyl the formation of CH2(X3B1) with LMR absorption technique.The branching ratios of collision induced intersystem crossing versus total consumption of 1CH2 are 0.14, 0.32, 0.67, 0.46 and 0.29 for the five reactants.
- Koch, M.,Temps, F.,Wagener, R.,Wagner, H. Gg.
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p. 645 - 650
(2007/10/02)
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- Studies on the Thermal Conversion of Long-chain Alkynes at High Temperatures in the Gas Phase
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In the gas phase pyrolysis of long-chain alkynes C5 to C9 at 773 to 873 K, a remarkable portion of molecular reaction (retro-ene analogous decompositions as well as cycloisomerizations of the parent alkynes to cyclopentenes alkylated in 3-position) takes place besides the thermal conversion of the starting compounds via radical chain processes.The different products were separated by GC and the main products identified by means of different methods.The mechanisms of formation of the major products are discussed.
- Ondruschka, B.,Zimmermann, G.,Ziegler, U.,Kopinke, F.-D.,Teuber, M.
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p. 273 - 284
(2007/10/02)
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- Rates of Base-Catalyzed Hydrogen Exchange of Terminal Acetylenes in Aqueous Solution. Absence of Resonance Interaction
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Rates of detritiation of 13 monosubstituted acetylenes labeled at the acetylenic hydrogen position were measured in aqueous amine buffer solution at 25 deg C, and hydroxide ion catalytic coefficients were evaluated.These rate constants, plus a few additional values from the literature, give a good correlation against inductive or field substituent constants: log(kHO-/M-1s-1) = 1.46+/-0.12 + (8.00+/-0.50)?I.This correlation is not improved by addition of resonance substituted constants, and the coefficients of the resonance term in two different dual parameter (resonance plus field) treatments of the data are in fact zero.
- Kresge, A. J.,Powell, M. F.
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p. 819 - 822
(2007/10/02)
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- A New General Synthesis of Aliphatic and Terminal Alkynes: Flash Vacuum Pyrolysis of β-Oxoalkylidenetriphenylphosphoranes
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By using flash vacuum conditions the thermal elimination of Ph3PO from β-oxoalkylidenetriphenylphosphoranes, previously confined to cases with an α-electron withdrawing group, has been extended to provide a general, high yielding synthesis of aliphatic and terminal alkynes.
- Aitken, R. Alan,Atherton, J. Ian
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p. 1140 - 1141
(2007/10/02)
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- L'isomerisation de radicaux insatures. II. Les radicaux α-ethallyles et α,γ-dimethallyles formes dans la photolyse de l'hexene-3 et du methyl-4-pentene-2 a 147,0 et 184,9 nm
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The photolysis of cis-3-hexene and 4-methyl-cis-2-pentene has been studied at 147.0 and 184.9 nm.The fragmentation pattern of the photoexcited molecule is normal: it requires, mainly , the split of a C-C bond located in the β position relative to the double bond (ca. 80percent).Some α(C-C), β(C-H), and α(C-H) primary splits complete this mechanism.The formation of α-ethallyl and α,γ-dimethallyl radicals is improtant in 3-hexene and 4-methyl-2-pentene, respectively.An isomerization process, involving these two radicals, is necessary to explaine the formation of part of the 1,3-pentadiene in the 3-hexene system and of all the 1,3-butadiene in the 4-methyl-2-pentene system.This process involves a 1,4-hydrogen atom transfer.
- Collin, Guy J.,Deslauriers, Helene
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p. 944 - 950
(2007/10/02)
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