Olefinic Double Bond Research Articles

Advanced production process of jet fuel components from technical grade coconut oil with special hydrocracking

The quality requirements for jet fuels have become stricter in the last few years. The reason of this is that more severe environmental regulations have been introduced and the increasing demand for performance requirements. Furthermore another requirement for jet fuels is that they should contain components of alternative origin to fulfil the requirements of the standard and to contribute to CO2 reduction. The aim of our experimental work was to study the production of jet fuel from natural triglycerides (technical grade coconut oil) with special hydrocracking (hydrogenation of olefinic double bonds, propane split, hydrodeoxygenation, decarbonylation and decarboxylation) with lower chemical and energy costs, less harmful material emission and better economy. Experiments were carried out on a sulfided NiMo/Al2O3 catalyst at different process parameters (temperature: 280–380°C, pressure: 30bar, liquid hourly space velocity: 1.0–3.0h−1, H2/feedstock volume ratio: 600Nm3/m3). Two possibilities for keeping the catalyst in sulfide-state during the special hydrocracking were investigated. These are the H2S containing hydrogen gas and the liquid sulfidation agent (dimethyl-disulfide). It was found that at the favourable process parameters (temperature 360°C, pressure 30bar, liquid hourly space velocity: 1.0h−1, H2/feedstock volume ratio 600Nm3/m3) the product yields were higher with 0.5–2.0absolute % in case of H2S containing hydrogen gas application. The jet fuel fractions were mixtures of saturated straight chain hydrocarbons; they were aromatic and olefin free, so they have excellent oxidation stability. The highest difference in the quality of jet fuel fractions obtained by the dimethyl-disulfide and H2S containing gas application was the sulfur content of the products (⩽2mg/kg with H2S, 7–9mg/kg with dimethyl-disulfide). The freezing point of jet fuel fractions obtained by special hydrocracking was high either when using dimethyl-disulfide or hydrogen-sulfide sulfidating agents (−11°C with H2S and −8°C with dimethyl-disulfide) compared to the value of the standard (maximum −47°C). Isomerisation on Pt/SAPO-11 catalyst was used to decrease the freezing point of the high n-paraffin containing jet fuel fractions resulting in products of freezing points of −45°C to −41°C (T=360°C, P=45bar, liquid hourly space velocity=1.1h−1, H2/feedstock ratio=350Nm3/m3). These values can be further decreased by using low level additivation (15mg/kg and 20mg/kg) to −49°C and −48°C respectively. These products fulfil the standard requirement.It was concluded that H2S containing H2 gas forming as a side product during the desulfurization of jet fraction or diesel fuel in a crude oil refinery is useful to maintain the sulfide-state of the catalyst. A further advantage is that there is no need to extract the H2S from this gas stream with absorption/desorption. This means significant chemical and operation cost decreasing, less energy consumption, moreover less harmful material emission. This solution can be integrated easily in the structure of a crude oil refinery.

Organoplatinum(II) Complexes Featuring the 2‐Vinylpyridine Ligand

AbstractRoom temperature reaction of 2‐vinylpyridine ligand (L, 2 equiv.) with the known dimethylplatinum(II) complex cis,cis‐[Me2Pt(µ‐SMe2)2PtMe2], A, provided a novel dimeric platinum(II) complex [PtMe2(µ2‐η1:η2‐2‐vpy)]2, 2, by displacement of the dimethyl sulfide (SMe2) ligands with the nitrogen atom and the olefinic double bond donors of 2‐vpy. The single crystal structure of complex 2 reveals a distorted square‐planar geometry around platinum centers. Two L groups in this complex act as bridging ligands between platinum centers, displaying a short Pt⋅⋅⋅Pt interaction with unique orientation in a head‐to‐tail (HT) arrangement. Complex 2 was not stable in dimethyl sulfoxide (dmso) solution, and through C‐H bond activation produced methane and cyclometalated complex [PtMe(η1:η1‐2‐vpy)(dmso)], 1.

An easy approach to dihydrochalcones via chalcone in situ hydrogenation

Abstract Dihydrochalcones are polyphenols that exhibit a diversity of bioactivities, namely anti-inflammatory, antimicrobial and antiviral. We have explored the synthetic access to such molecular entities, and describe now an easy and scalable approach based on reduction of the olefinic double bond of chalcone precursors via in situ hydrogenation with the system Et3SiH-Pd/C in very high yield. The intermediate chalcones were synthesized also by a simple and efficient microwave-assisted Claisen–Schmidt condensation of aromatic aldehydes with acetophenones, conveniently protected with ethoxymethyl ether, if required. Chalcones were obtained as single reaction product in high yield in 2–3 h, while under conventional conditions at room temperature the reaction was carried out with completion only after 24 h. In addition, microwave irradiation has proven very efficient for deprotection of ethoxymethyl ether with iron chloride in only 10 min and very high yield.

Two-dimensional gas chromatography-online hydrogenation for improved characterization of petrochemical samples

The Fischer-Tropsch (FT) process produces a variety of hydrocarbons over a wide carbon number range and during subsequent product workup a large variety of synthetic fuels and chemicals are produced. The complexity of the product slate obtained from this process is well documented and the high temperature FT (HT-FT) process products are spread over gas, oil and water phases. The characterization of these phases is very challenging even when using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS). Despite the increase in separation power, peak co-elution still occurs when samples containing isomeric compounds are analysed by comprehensive two dimensional GC. The separation of isomeric compounds with the same double bond equivalents is especially difficult since these compounds elute in a similar position on the GC×GC chromatogram and have identical molecular masses and similar fragmentation patterns in their electron ionization (EI) mass spectra. On-line hydrogenation after GC×GC separation is a possible way to distinguish between these isomeric compounds since the number of rings and alkene double bonds can be determined from the mass spectra of the compounds before and after hydrogenation. This paper describes development of a GC×GC method with post column hydrogenation for the determination of the backbone of cyclic/olefinic structures enabling us to differentiate between classes like dienes and cyclic olefins in complex petrochemical streams.

Copolymerizations of Norbornene and Tetracyclododecene with α-Olefins by Half-Titanocene Catalysts: Efficient Synthesis of Highly Transparent, Thermal Resistance Polymers

Highly efficient synthesis of cyclic olefin (CO) copolymers with high glass transition temperatures (Tg) as well as high catalytic activity have been attained not only by copolymerization of norbornene (NBE) with α-olefins (1-hexene, 1-octene, 1-dodecene), but also by copolymerization of tetracyclododecene (TCD) with α-olefins using half-titanocene catalysts, Cp′TiCl2(N═CtBu2) [Cp′ = tBuC5H4 (1), Cp (2)] in the presence of MAO. Linear relationships between the Tg values and the NBE or TCD contents were observed in all cases; Tg values in poly(TCD-co-α-olefin)s were higher than those in poly(NBE-co-α-olefin)s with the same CO contents. NBE and TCD incorporations in these copolymerization under high NBE or TCD feed conditions (especially by 2) were not affected by α-olefin (number of methylene units in the side chain) employed. An introduction of terminal olefinic double bond into the polymer side chain could be attained, if the copolymerization of NBE with 1-octene by 1 was conducted in the presence of 1,7...

ChemInform Abstract: Oxygen‐Chelated Indenylidene Ruthenium Catalysts for Olefin Metathesis

AbstractReview: [55 refs.

Deciphering the Mechanism Involved in the Switch On/Off of Molecular Pistons

AbstractManufacturing machines converting energy to mechanical work at the molecular level is a vital pathway to explore the microscopic world. A kind of operable molecular engines, composed of β‐cyclodextrin (β‐CD), aryl, alkene and amide moiety was investigated using molecular dynamics simulations combined with free‐energy calculations. To understand how the integrated alkene double bond controls the work performed on the engines, two alkene isomers of the prototype were considered as two molecular engines. The free‐energy profiles delineating the binding process of the amide (Z)‐ and (E)‐isomers for each alkene isomer with 1‐adamantanol indicate that for the alkene (E)‐isomer, the apparent work performed on the amide bond is 1.6 kcal/mol, while the alkene (Z)‐isomer is incapable to perform work. Direct switch on/off of engines caused by the isomerization of the alkene bond was, therefore, witnessed, in line with experimental measurements. Decomposition of the free‐energy profile into different components and structural analyses suggest that the isomerization of the alkene bond controls the position of the aryl unit relative to the cavity of the CD, resulting in the difference among the free‐energy profiles and the stark contrast of the work performed on engines.

Control of ozonolysis kinetics and aerosol yield by nuances in the molecular structure of volatile organic compounds

Abstract Secondary organic aerosol (SOA) plays integral roles in climate and human health, yet there remains a limited understanding of the mechanisms that lead to its formation and ultimate fate, as evidenced by a disparity between modeled atmospheric SOA loadings and field measurements. This disparity highlights the need for a more accurate representation of the molecular-level interactions between SOA sources and oxidative pathways. Due to the paucity of detailed chemical data for most SOA precursors of atmospheric relevance, models generally predict SOA loadings using structure activity relationships generalized to classes of SOA precursors. However, the kinetics and SOA forming potential of molecules are nuanced by seemingly minor structural differences in parent molecules that may be neglected in models. Laboratory chamber studies were used to measure SOA yields and rate constants for the ozonolysis of several linear, cyclic and oxygenated C5–C7 alkenes whose molecular structure vary in the site of unsaturation and/or the presence/position of functional groups and that represent atmospherically relevant classes of molecules. For the alkenes studied in this work, we found greater SOA yields for cyclic compounds compared to their linear analogs. For 1-alkenes, SOA yield increased with carbon number but was also dependent on the position of the double bond (internal vs terminal). Both the identity and position of oxygenated functional groups influenced SOA yield and kinetics through steric and electronic effects. Additionally, terminal alkenes generally resulted in a greater SOA yield than analogous internal alkenes, indicating that the position of the double bond in alkenes plays an important role in its atmospheric fate. Herein, we demonstrate the nuanced behavior of these ozonolysis reactions and discuss relationships between parent compound molecular structure and SOA yield and kinetics.

Rapid Identification and Quantification of Linear Olefin Isomers by Online Ozonolysis-Single Photon Ionization Time-of-Flight Mass Spectrometry.

The specific locations of the double bonds in linear olefins can facilitate olefin catalytic synthetic reactions to improve the quality of target olefin products. We developed a simple and efficient approach based on single photon ionization time-of-flight mass spectrometry (SPI-TOFMS) combined with online ozonolysis to identify and quantify the linear olefin double bond positional isomers. The online ozonolysis cleaved the olefins at the double bond positions that led to formation of corresponding characteristic aldehydes. The aldehydes were then detected by SPI-TOFMS to achieve unique spectrometric "fingerprints" for each linear olefin to successfully identify the isomeric ones. To accurately quantify the isomeric components in olefin mixtures, an algorithm was proposed to quantify three isomeric olefin mixtures based on characteristic ion intensities and their equivalent ionization coefficients. The relative concentration errors for the olefin components were lower than 2.5% while the total analysis time was less than 2 min. These results demonstrate that the online ozonolysis SPI-TOFMS has the potential for real-time monitoring of catalytic olefin synthetic reactions.

Selective synthesis of alkylboronates by copper(I)-catalyzed borylation of allyl or vinyl arenes.

An efficient copper-catalyzed borylation reaction of allyl or vinyl arenes with bis(pinacolato)diboron has been developed, without using ligands. Markovnikov-selectivity is observed in the borylation of allyl arenes with bis(pinacolato)diboron, while the regioselectivity is completely opposite when styrene derivatives are used as substrates. A mechanism involving Cu-B species regioselectively adding olefin double bonds to form the alkylcopper or η(3)-benzyl copper intermediate, which is followed by protonation to obtain products, is proposed.

Aggregation-Induced Fluorescence Emission Properties of Dicyanomethylene-1,4-dihydropyridine Derivatives

A series of dicyanomethylene-1,4-dihydropyridine (DCMP) derivatives with aggregation-induced emission (AIE) were designed and synthesized. These target compounds emit low fluorescence in THF solutions because of the free rotation of the phenyl and dihydropyridine rings about the axes of the olefinic double bonds and the resultant nonradiative decay process, but they exhibit strong fluorescence in the aggregate state because of the restriction of intramolecular rotation (RIR), as confirmed by solution thickening and cooling experiments. Compared with the almost-planar dicyanomethylene-4H-pyran (DCM) derivative DCM-1 with aggregation-caused quenching (ACQ), DCMP-5 with AIE takes a highly twisted conformation by replacing the oxygen atom of the DCM skeleton with an N-ethyl group, as revealed by crystallographic data and theoretical calculations. Depending on the different electron-donating substituents, the solids of these compounds emit yellow or orange fluorescence. Moreover, the cyano group endows DCMP-5 with a strong self-assembly ability under proper conditions, and the obtained regular microparticles emit bright orange fluorescence. These materials will broaden the new family of AIE-exhibiting fluorophores.

Immobilization of Ag(i) into a metal-organic framework with -SO3H sites for highly selective olefin-paraffin separation at room temperature.

Introduction of Ag(i) ions into a sulfonic acid functionalized MOF ((Cr)-MIL-101-SO3H) significantly enhances its interactions with olefin double bonds, leading to its much higher selectivities for the separation of C2H4-C2H6 and C3H6-C3H8 at room temperature over the original (Cr)-MIL-101-SO3H and other adsorbents at room temperature.

Sunlight-induced covalent marriage of two triply interlocked Pd6 cages and their facile thermal separation.

A template-free triply interlocked Pd6 cage (2) was synthesized by two-component self-assembly of cis-blocked 90° acceptor cis-(tmen)Pd(NO3)2 (M) and 1,3,5-tris((E)-2-(pyridin-3-yl)vinyl)benzene (L). Assembly 2 was characterized by (1)H NMR and ESI-MS, and the structure was confirmed by X-ray crystallography, which revealed a parallel conformation of the olefin double bonds belonging to the adjacent cages in the solid state at a distance of 3.656 Å, thereby indicating the feasibility of [2+2] photochemical reaction. Two adjacent interlocked cages were covalently married together by intermolecular [2+2] cycloaddition in a single crystal-to-single crystal fashion upon exposure to sunlight/UV irradiation. Most surprisingly, the covalently married pair was easily separated thermally in aqueous medium under mild reaction conditions.

Univalent gallium complexes of simple and ansa-arene ligands: effects on the polymerization of isobutylene.

Using [Ga(C6 H5 F)2 ](+) [Al(OR(F))4 ](-) (1) (R(F) =C(CF3)3) as starting material, we isolated bis- and tris-η(6) -coordinated gallium(I) arene complex salts of p-xylene (1,4-Me2 C6 H4), hexamethylbenzene (C6 Me6 ), diphenylethane (PhC2 H4 Ph), and m-terphenyl (1,3-Ph2 C6 H4): [Ga(1,4-Me2 C6 H4 )2.5 ](+) (2(+)), [Ga(C6 Me6 )2 ](+) (3(+)), [Ga(PhC2 H4 Ph)](+) (4(+)) and [(C6 H5 F)Ga(μ-1,3-Ph2 C6 H4)2 Ga(C6 H5 F)](2+) (5(2+)). 4(+) is the first structurally characterized ansa-like bent sandwich chelate of univalent gallium and 5(2+) the first binuclear gallium(I) complex without a Ga-Ga bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI-BP86/SV(P) level), [Ga(PhC2 H4 Ph)](+) [Al(OR(F))4](-) (4) and [(C6 H5 F)Ga(μ-1,3-Ph2 C6 H4)2 Ga(C6 H5 F)](2+) {[Al(OR(F) )4] (-)}2 (5), featuring ansa-arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR-PIB). In comparison to the recently published 1 and the [Ga(1,3,5-Me3 C6 H3)2](+) [Al(OR(F))4](-) salt (6) (1,3,5-Me3 C6 H3 =mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR-PIB with high contents of terminal olefinic double bonds (α-contents=84-93 %), low molecular weights (Mn =1000-3000 g mol(-1)) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6, the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.

Univalent Gallium Complexes of Simple and ansa-Arene Ligands: Effects on the Polymerization of Isobutylene.

Using [Ga(C6 H5 F)2 ]+ [Al(ORF )4 ]- (1) (RF =C(CF3 )3 ) as starting material, we isolated bis- and tris-η6 -coordinated gallium(I) arene complex salts of p-xylene (1,4-Me2 C6 H4 ), hexamethylbenzene (C6 Me6 ), diphenylethane (PhC2 H4 Ph), and m-terphenyl (1,3-Ph2 C6 H4 ): [Ga(1,4-Me2 C6 H4 )2.5 ]+ (2+ ), [Ga(C6 Me6 )2 ]+ (3+ ), [Ga(PhC2 H4 Ph)]+ (4+ ) and [(C6 H5 F)Ga(μ-1,3-Ph2 C6 H4 )2 Ga(C6 H5 F)]2+ (52+ ). 4+ is the first structurally characterized ansa-like bent sandwich chelate of univalent gallium and 52+ the first binuclear gallium(I) complex without a GaGa bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI-BP86/SV(P) level), [Ga(PhC2 H4 Ph)]+ [Al(ORF )4 ]- (4) and [(C6 H5 F)Ga(μ-1,3-Ph2 C6 H4 )2 Ga(C6 H5 F)]2+ {[Al(ORF )4 ] - }2 (5), featuring ansa-arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR-PIB). In comparison to the recently published 1 and the [Ga(1,3,5-Me3 C6 H3 )2 ]+ [Al(ORF )4 ]- salt (6) (1,3,5-Me3 C6 H3 =mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR-PIB with high contents of terminal olefinic double bonds (α-contents=84-93 %), low molecular weights (Mn =1000-3000 g mol-1 ) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6, the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.

Identification and cloning of an NADPH-dependent hydroxycinnamoyl-CoA double bond reductase involved in dihydrochalcone formation in Malus × domestica Borkh.

The apple tree (Malus sp.) is an agriculturally and economically important source of food and beverages. Many of the health beneficial properties of apples are due to (poly)phenolic metabolites that they contain, including various dihydrochalcones. Although many of the genes and enzymes involved in polyphenol biosynthesis are known in many plant species, the specific reactions that lead to the biosynthesis of the dihydrochalcone precursor, p-dihydrocoumaroyl-CoA (3), are unknown. To identify genes involved in the synthesis of these metabolites, existing genome databases of the Rosaceae were screened for apple genes with significant sequence similarity to Arabidopsis alkenal double bond reductases. Herein described are the isolation and characterization of a Malus hydroxycinnamoyl-CoA double bond reductase, which catalyzed the NADPH-dependent reduction of p-coumaroyl-CoA and feruloyl-CoA to p-dihydrocoumaroyl-CoA and dihydroferuloyl-CoA, respectively. Its apparent Km values for p-coumaroyl-CoA, feruloyl-CoA and NADPH were 96.6, 92.9 and 101.3μM, respectively. The Malus double bond reductase preferred feruloyl-CoA to p-coumaroyl-CoA as a substrate by a factor of 2.1 when comparing catalytic efficiencies in vitro. Expression analysis of the hydroxycinnamoyl-CoA double bond reductase gene revealed that its transcript levels showed significant variation in tissues of different developmental stages, but was expressed when expected for involvement in dihydrochalcone formation. Thus, the hydroxycinnamoyl-CoA double bond reductase appears to be responsible for the reduction of the α,β-unsaturated double bond of p-coumaroyl-CoA, the first step of dihydrochalcone biosynthesis in apple tissues, and may be involved in the production of these compounds.

Bismuth(III) triflate-catalyzed synthesis of substituted 2-alkenylfurans.

A convergent synthesis of the title compounds is reported, which relies on a successive 2-fold SN'-type substitution reaction at methoxy-substituted propargylic acetates. The furan C3-C4 bond is presumably established by silyl enol ether attack at a propargylic cation intermediate. The resulting α-methoxyallene is intramolecularly substituted, leading to cyclization by displacement of the methoxy group (O-C2 bond formation) and to simultaneous formation of the exocyclic alkene double bond. Despite the relatively mild conditions, the reactions were complete within 5 min.

Efficient Terpolymerization of Ethylene and Styrene with 1,7‐Octadiene by Aryloxo Modified Half‐Titanocenes–Cocatalyst Systems: Efficient Introduction of the Reactive Functionality

Terpolymerization of ethylene and styrene (St) with 1,7‐octadiene (OD) using aryloxo‐modified half‐titanocenes, Cp′ TiCl2(O‐2,6‐iPr2C6H3) [Cp′ = Cp* (1), tBuC5H4 (2), 1,2,4‐Me3C5H2 (3)], proceeds with high catalytic activity and efficient comonomer incorporation, affording high‐molecular‐weight polymers with unimodal molecular‐weight distributions (uniform compositions). An efficient introduction of the reactive functionality, terminal olefinic double bonds, into the side‐chain is attained by adopting this method by incorporation of OD without cyclization: the comonomer contents (St, OD) can be controlled by varying the comonomer concentration charged. The resultant polymers possess negligible resonance, ascribed to St–OD repeated insertion. image

Methyl (E)-3-(2-formyl-phen-oxy)acrylate.

In the title compound, C11H10O4, the methyl acrylate sub­stituent adopts an extended E conformation with all torsion angles close to 180°. The conformation of the keto group with respect to the olefinic double bond is typically S-trans. In the crystal, mol­ecules are linked via pairs of C—H⋯O hydrogen bonds, forming inversion dimers with an R 2 2(8) graph-set motif. The dimers are further linked via C—H⋯O hydrogen bonds, forming chains along [001], which enclose R 3 2(16) graph-set ring motifs. The keto group O atomaccepts two C—H⋯O interactions.

Mechanistic Insights into Carbonyl-Directed Rhodium-Catalyzed Hydroboration: ab Initio Study of a Cyclic γ,δ-Unsaturated Amide.

A two-point binding mechanism for the cationic rhodium(I)-catalyzed carbonyl-directed catalytic asymmetric hydroboration of a cyclic γ,δ-unsaturated amide is investigated using density functional theory. Geometry optimizations and harmonic frequency calculations for the model reaction are carried out using the basis set 6-31+G** for C, O, P, B, N, and H and LANL2DZ for Rh atoms. The Gibbs free energy of each species in THF solvent is obtained based on the single-point energy computed using the PCM model at the ECP28MWB/6-311+G(d,p) level plus the thermal correction to Gibbs free energy by deducting translational entropy contribution. The Rh-catalyzed reaction cycle involves the following sequence of events: (1) chelation of the cyclic γ,δ-unsaturated amide via alkene and carbonyl complexation in a model active catalytic species, [Rh(L2)2S2]+, (2) oxidative addition of pinacol borane (pinBH), (3) migratory insertion of the alkene double bond into Rh–H (preferred pathway) or Rh–B bond, (4) isomerization of the resulting intermediate, and finally, (5) reductive elimination to form the B–C or H–C bond with regeneration of the catalyst. Free energy profiles for potential pathways leading to the major γ-borylated product are computed and discussed in detail. The potential pathways considered include (1) pathways proceeding via migratory insertion into the Rh–H bond (pathways I, I-1, and I-2), (2) a potential pathway proceeding via migratory insertion into the Rh–B bond (pathway II), and two potential competing routes to a β-borylated byproduct (pathway III). The results find that the Rh–H migratory insertion pathway I-2, followed in sequence by an unanticipated isomerization via amide rotation and reductive elimination, is the most favorable reaction pathway. A secondary consequence of amide rotation is access to a competing β-hydride elimination pathway. The pathways computed in this study are supported by and help explain related experimental results.