592-48-3Relevant academic research and scientific papers
Dissociation of 1,3-Hexadiene and the Resonance Energy of the Pentadienyl Radical
Trenwith, Antony B.
, p. 266 - 271 (1980)
Measurements of the rate at which methane is formed in the pyrolysis of 1,3-hexadiene at temperatures over the range 694-759 K and pressures between 25 and 200 Torr show that the dissociation reaction CH3CH2CH=CHCH=CH2 -> CH3.+ .CH2CH=CHCH=CH2 is a homogeneous, first-order reaction under these conditions and the rate expression is log(k1/s-1) = (15.92 +/- 0.17)-(66390 +/- 840)/θ where θ = 2.303RT/cal mol-1 (1 cal = 4.18 J).The experimental activation energy yields for the pentadienyl radical, ΔH = 45.9 +/- 1.0 kcal mol-1 at 298 K and a resonance energy of 18.5 +/- 1.5 kcal mol-1, assuming a value of 98.2 kcal mol-1 for the primary C-H bond dissociation energy in alkenes.
Direct and Selective Synthesis of Adipic and Other Dicarboxylic Acids by Palladium-Catalyzed Carbonylation of Allylic Alcohols
Beller, Matthias,Ge, Yao,Huang, Weiheng,Jackstell, Ralf,Liu, Jiawang,Neumann, Helfried,Yang, Ji
supporting information, p. 20394 - 20398 (2020/09/21)
A general and direct synthesis of dicarboxylic acids including industrially important adipic acid by palladium-catalyzed dicarbonylation of allylic alcohol is reported. Specifically, the combination of PdCl2 and a bisphosphine ligand (HeMaRaphos) promotes two different carbonylation reactions with high activity and excellent selectivity.
Method for synthesizing diene compounds based on aldehyde-ketone condensation reaction
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, (2019/05/08)
The invention provides a method for synthesizing diene compounds based on an aldehyde-ketone condensation reaction. The method comprises the following steps: firstly, under the action of a condensation catalyst, performing a condensation reaction on ketone compounds and aldehyde compounds to obtain condensation products; then, under the action of a reduction catalyst, performing a reduction reaction on the condensation products obtained in the previous step to obtain reduction products; under the action of a catalyst, performing a dehydration reaction on the reduction products obtained in theprevious step to obtain the diene compounds. According to the method, ketone, aldehyde as well as homologues of ketone and aldehyde which are cheap and easy to obtain can be used as raw materials forsynthesizing the diene compounds such as butadiene, piperylene as well as homologues of butadiene and piperylene, experimental conditions are mild, the operation is simple, and a large-scale synthesisprospect is achieved.
Tetrabutylphosphonium Bromide Catalyzed Dehydration of Diols to Dienes and Its Application in the Biobased Production of Butadiene
Stalpaert, Maxime,Cirujano, Francisco G.,De Vos, Dirk E.
, p. 5802 - 5809 (2017/09/15)
We report the use of the ionic liquid tetrabutylphosphonium bromide as a solvent and catalyst for dehydration of diols to conjugated dienes. This system combines stability, high reaction rates, and easy product separation. A reaction mechanism for the model compound 1,2-hexanediol is proposed and experimentally corroborated. This particular mechanism allows for the selective formation of conjugated dienes, in contrast with purely acidic catalysis. Next, the reaction is also performed on various other diols. As a first application, we assessed the biobased production of 1,3-butadiene. With 1,4-butanediol as the starting material, a 94% yield of butadiene was reached at 100% conversion.
Ring Opening of Biomass-Derived Cyclic Ethers to Dienes over Silica/Alumina
Kumbhalkar, Mrunmayi D.,Buchanan, J. Scott,Huber, George W.,Dumesic, James A.
, p. 5248 - 5256 (2017/08/17)
We show that cyclic ethers, such 2-methyltetrahydrofuran (2-MTHF), can undergo dehydration to produce pentadienes over SiO2/Al2O3. The catalyst exhibited reversible deactivation due to coke deposition, with the yield to pentadienes decreasing from 68% to 52% at 623 K over 58 h time on stream. A reaction network for 2-MTHF dehydration was proposed on the basis of the results of space time studies. Pentadienes can be produced directly by a concerted hydride shift and dehydration of carbenium intermediates or indirectly through dehydration of pentanal and pentenol. Reaction kinetics studies were performed at temperatures ranging from 573 to 653 K and 2-MTHF partial pressures from 0.21 to 2.51 kPa. The apparent activation energy barrier for 2-MTHF conversion to pentadienes and the reaction rate order for ring opening were determined to be 74 kJ mol-1 and 0.24, respectively, indicating strong interaction between 2-MTHF and the SiO2/Al2O3 surface. Other solid acids such as γ-Al2O3, H-ZSM-5, and Al-Sn-Beta were found to be active for 2-MTHF dehydration to pentadienes. The rate of ring opening decreased in the order 2,5-dimethyltetrahydrofuran > 2-MTHF > tetrahydropyran > tetrahydrofuran. Over SiO2/Al2O3, the dehydration of 2,5-dimethyltetrahydrofuran resulted in 75% yield to hexadiene isomers. (Figure Presented).
CATALYTIC DEHYDRATION OF ALCOHOLS AND ETHERS OVER A TERNARY MIXED OXIDE
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Paragraph 0043; 0046, (2013/03/28)
A ternary V—Ti—P mixed oxide is shown to catalytically dehydrate 2-methyl-tetrahydrofuran in high conversion to give piperylene, in good yield. Volatile products collected from this reaction contain piperylene in concentrations as high as 80 percent by weight. Dehydration of glycerol to acrolein in high conversion and moderate selectivity is also demonstrated. The catalyst is also shown to dehydrate other alcohols and ether substrates. The catalyst is resistant to deactivation and maintains activity between runs.
Kinetics and modeling of the thermal reaction of propene at 800 K. Part III. Propene in the presence of small amounts of oxygen
Barbe,Baronnet,Martin,Perrin
, p. 503 - 522 (2007/10/03)
The thermal reaction of propene was studied around 800 K in the presence of less than 20% O. Initially, the production of H2, CH4, C2H4, C2H6, allene, C3H8, 1,3-butadiene, butenes, 3- and 4-methylcyclopentene, a mixture of 1,4- and 1,5-hexadienes, methylcyclopentane, 4-methylpent-1-ene, and hex-1-ene, was observed along with H2O2, CO, and small quantities of ethanal and CO2. O increases the initial production of H and of most hydrocarbons and, particularly, that of C6 dienes and of cyclenes. A kinetic scheme is proposed in which chains are primarily initiated by a bimolecular step which competes with the second-order initiation of propene pyrolysis. Modeling of the reaction based on the proposed scheme accounts well for the concentration-time profiles.
Addition of Dimethylsilanediyl (Dimethylsilylene) to cis,cis-Hexa-2,4-diene: Evidence for a Concerted Vinylsilacyclopropane Rearrangement
Lei, Deqing,Gaspar, Peter P.
, p. 1149 - 1151 (2007/10/02)
The formation of cis-3,3-dimethyl-3-silahepta-1,4-diene as the major product from addition of dimethylsilanediyl (dimethylsilylene) to cis,cis-hexa-2,4-diene is believed to result from a concerted 1,5-sigmatropic hydrogen shift in the rearrangement of the vinylsilacyclopropane intermediate formed by concerted 1,2-cis-addition of the silanediyl.
Tellurolate-Induced 1,4-Elimination of 1,4-Dibromo-2-Enes. Syntheses of 1,3-Dienes
Engman, Lars,Bystroem, Styrbjoern E.
, p. 3170 - 3174 (2007/10/02)
Sodium 2-thienyltellurolate, generated in catalytic amounts from sodium borohydride and bis(2-thienyl) ditelluride, was found to efficiently debrominate 1,4-dibromo-2-olefins to 1,3-dienes under very mild reaction conditions.The required 1,4-dibromo-2-olefins were usually synthesized by allylic α,α'-bromination of olefins.Terminal olefins yielded, via allylic rearrangement, a mixture of 1,4-dibromo-2-olefins and 1,2-dibromo-3-olefins.Both these isomers were converted to 1,3-dienes (E/Z ca. 9/1) by the tellurolate reagent.The syntetic utility of the tellurolate-induced debromination reaction was demonstrated in a two-step synthesis of the main component of the red bollworm moth sex pheromone.
Titanium Catalyzed Cyclization of 1,5-Hexadienes
Lehmkuhl, Herbert,Tsien, Yen-Lung
, p. 2437 - 2446 (2007/10/02)
Cp2TiCl (1) and Cp2TiCl2 (2) combined with isopropylmagnesium bromide (molar ratio 1:1 and 1:2, resp.) catalyze the conversion of 1,5-hexadiene into a mixture of the five-membered ring compounds 3 and 4 as well as the linear isomeric hexadienes 5, 6, and 7.THF is most effective in both promoting cyclization as well as suppressing isomerization (3 -> 4 and 5 -> 6 or 7).The ratio of cyclic to linear products in reactions involving substituted 1,5-hexadienes is found to be dependent upon the position of the substituents.Substitution in the 2- or 2- and 5-position leads to the formation of the open-chain isomers 11 and 12 or 13 and 14, while 3,4-substituted 1,5-hexadienes react to give > 99percent of the five-membered ring systems 15 and 16 or 17 and 18.A reaction mechanism is discussed which involves Cp2TiH and Cp2(alkenyl)Ti intermediates.
