Ethylenic Double Bond Research Articles

Mono- and dinuclear metallacyclic complexes of Pt(II) synthesized from some eugenol derivatives

The complexes K[PtCl3(Meug)] (1; Meug = methyleugenol), K[PtCl3(Meteug)] (2; Meteug = methyl eugenoxyacetate), and K[PtCl3(Eteug)] (3; Eteug = ethyl eugenoxyacetate) reacted with AgNO3, SnCl2, KOH, or ethanol–water solutions to lose one aryl proton and form dinuclear metallacyclic complexes Pt2Cl2(Meug-1H)2 (4), Pt2Cl2(Meteug-1H)2 (5), and Pt2Cl2(Eteug-1H)2 (6), respectively. Complexes 4–6 reacted with aliphatic, aromatic, and heterocyclic amines to give various mononuclear metallacyclic platinum complexes 7–15. 1H NMR spectra showed that in 4–15 Meug, Meteug, and Eteug are bound with Pt(II) both at the benzene carbon and at the ethylenic double bond of the side chain. NOESY spectra and single-crystal X-ray diffraction indicated that in 7–15 the amines are in cis-position with respect to the ethylenic double bond.

Recent Advances in Fast Gas-Chromatography: Application to the Separation of Fatty Acid Methyl Esters

Gas-chromatography (GC) is a powerful separation technique for resolving and quantifying a wide range of compounds, such as fatty acid methyl esters (FAME) derivatives. Separation of common FAME is typically achieved on highly polar or polyethylene glycol stationary phases that can separate fatty acids according to chain length, number and geometry of ethylenic double bonds. GC is one of the most commonly available methods for fatty acid analysis with constant improvements for different applications. One such improvement is faster GC analysis, which has long been the focus of investigators researching the application and benefits of this technique. A greater speed of analysis offers many key benefits, such as increased sample throughput, reduced analytical expenses, and increased laboratory productivity. Fast GC analysis can be accomplished by using a short column with reduced column film thickness, high carrier gas velocity, and fast program temperatures. A summary of options for fast GC analysis with emphasis on FAME analysis is discussed in the present review.

Comparison of thermal polymerization mechanisms for α-methylstyrene and trans-β-methylstyrene

The polymerization mechanisms of styrene and various derivatives by α-methylstyrene (AMS) and trans-β-methylstyrene (TBMS) were evaluated. Experiments were carried out for dimerization identification and thermal polymerization estimation by differential scanning calorimetry (DSC), thermal activity monitor (TAM) and Fourier transform infrared absorption spectrophotometer (FTIR). The results show that, under temperature ranges of 60–190 and 50–170°C, AMS and TBMS performed dimerization by benzene ring and ethylene double bond, respectively. AMS and TBMS would form unsaturated dimers, saturated dimers and trimers, etc., during the period of thermal polymerization. Through this study, one can estimate possible intermediates of the polymerization process for the monomer of interest in the petrochemical industry.

Formation of Metallacyclic Complexes by Activation of an Aryl C−H Bond in a Platinum−Safrole Analogue of Zeiseʼs Salt

Potassium trichloro(safrole)platinate(II), K[Pt(Saf)Cl3] (1), reacts with piperidine to give cis-[Pt(Saf-1H)(Piperidine)Cl] (2). The interaction of 1 with AgNO3, SnCl2, KOH, and ethanol−water solutions leads to formation of the dinuclear chelate ring complex [Pt2(Saf-1H)2Cl2] (3). 1H and 13C NMR spectra and single-crystal X-ray diffraction show that in complexes 2 and 3 deprotonated safrole is bound up with platinum(II) both at a benzene carbon and at the ethylenic double bond of the side chain.

Reaction Mechanism of Oxidation, Hydroxylation, and Epoxidation by Hypofluorous Acid: A Theoretical Study of Unusual H-Bond-Assisted Catalysis

The oxidation of organic molecules by hypofluorous acid (HOF) was studied extensively and systematically by Rozen et al. Therefore, it seems appropriate to refer to the process as Rozen oxidation. An entire set of model molecules was selected for quantum chemical investigation of the oxidation mechanism: a C=C double bond in ethylene, sulfur and selenium in dimethyl derivatives, nitrogen and phosphorus in trimethyl derivatives, as well as methyl azides. In the gas phase, van der Waals complexes between HOF and the previously mentioned species easily are formed, but these complexes are reluctant to undergo oxidation. The addition of another HOF molecule connected with the formation of a cyclic complex (i.e., substrate and two molecules of HOF) seems to be decisive for the oxidation process. The attempt to substitute the second HOF molecule with H2O demonstrated the superiority of HOF. Complexes of this kind decompose along the reaction path smoothly (i.e., with a low activation energy) to the respective oxidation product. A potential role of the hydroxyl cation (HO+) in the oxidation step is mentioned. Besides an oxidation product, one HOF molecule is released (an essential feature of catalysis), and furthermore, hydrogen fluoride is formed. It was suggested by Sertchook et al. (J. Phys. Chem. A 2006, 110, 8275) that the interaction between the substrate to be oxidized and HOF is catalytically influenced by the HF molecule. The mechanism suggested here is more feasible and, particularly at the early stages of the oxidation process, decisive. Also, the role of acetonitrile, used as a solvent by Rozen et al., is discussed in terms of a continuum model. Moreover, passing from potential energies to Gibbs energies is considered.

Isocyanatoethyl Methacrylate Telomerization and Cotelomerization

AbstractThis article describes the use of isocyanatoethyl methacrylate (IEM) as a monomer in telomerization and cotelomerization reactions. First, the selectivity of benzenethiol addition to the unsaturation of IEM is proven. Even with an equimolar amount of reactants, benzenethiol reacts almost selectively with the ethylenic double bonds. The radical telomerization of IEM and its cotelomerization with MMA, in the presence of benzenethiol, has been achieved and shows that control of molecular weight is possible. Finally, the addition of a phosphonated alcohol to these telomers, followed by ester cleavage reactions, leads selectively to families of mono or diphosphonate products. The study of the thermal properties of the cotelomers shows that the degradation starts at 180 °C on the isocyanate group of IEM, and then on the ester group of MMA, and the decomposition is complete at 450 °C. The introduction of the phosphonated ester group decreases the glass transition temperature of the cotelomers, but after hydrolysis these values increase.magnified image

Novel 1:1 Cocrystal of Benzoic Acid and 2-(Benzothiazol-2-yl)-1-phenylethenyl Benzoate

The crystal structure of a new benzoic acid cocrystal with a benzothiazole-based acceptor, 2-(benzothiazol-2-yl)-1-phenylethenyl benzoate (BEB), with the 1:1 stoichiometry, C7H6O2 + C22H15NO2S, has been determined. In the crystal lattice every benzoic acid molecule is associated to a (BEB) molecule via strong O-H…N and weak C-H…O intermolecular hydrogen bonds and two short intermolecular O-H…π contacts. In the structure of (BEB), due to an intra-molecular non-bonded S…O interaction, the intra-molecular S…O(1) non-bonded distance is shorter than the sum of the corresponding van der Waals radii and the Z configuration is preferred for the ethylenic double bond.

Non-resonance micro-Raman spectroscopic studies on crystalline domoic acid and its aqueous solutions

Domoic acid (DA) is a neurotoxin naturally present in the marine ecosystem. Since DA's toxicity has been explained by its molecular structure and particularly because of its ethylenic double bond, spectroscopic investigation of this molecule is of importance. We carried out Raman spectroscopy on crystalline DA and on DA in aqueous solutions (28,000–25 ng DA/mL) and assigned Raman modes in comparison with the Raman spectra of its substructures. Noise-free, clear Raman signal from the solutions containing low concentrations of DA were obtained by applying the drop coating deposition Raman (DCDR) technique. Raman spectra reveal that crystalline DA exists in the zwitterionic form. The Raman spectra of the DA aqueous solutions were analysed in the light of their pH whereas the variation in the spectra was attributed to the hydration, the degree of protonation and crystallinity of the solid film. We show that DCDR can be applied for the rapid detection of domoic acid down to 25 ng DA/mL (0.025 ppm).

Analysis of eicosapentaenoic and docosahexaenoic acid geometrical isomers formed during fish oil deodorization

Addition of long-chain polyunsaturated fatty acids (LC-PUFAs) from marine oil into food products implies preliminary refining procedures of the oil which thermal process affects the integrity of LC-PUFAs. Deodorization, the major step involving high temperatures, is a common process used for the refining of edible fats and oils. The present study evaluates the effect of deodorization temperature on the formation of LC-PUFA geometrical isomers. Chemically isomerized eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were used as reference samples. Fish oil samples have been deodorized at 180, 220 and 250 °C for 3 h and pure EPA and DHA fatty acid methyl esters (FAMEs) were chemically isomerized using p-toluenesulfinic acid as catalyst. FAMEs prepared from fish oil were fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC). Geometrical isomers produced by both processes were fractionated by silver-ion thin-layer chromatography (Ag-TLC) and silver-ion high-performance liquid chromatography (Ag-HPLC). The FAME fractions were subsequently analyzed by gas chromatography (GC) on a 100 m highly polar cyanopropylpolysiloxane coated capillary column, CP-Sil 88. Our results show that thermally induced geometrical isomerization appears to be a directed reaction and some ethylenic double bond positions on the hydrocarbon chain are more prone to stereomutation. Only minor changes were observed in the EPA and DHA trans isomers content and distribution after deodorization at 180 °C. The analyses of EPA and DHA isomer fractions revealed that it is possible to quantify EPA geometrical isomers by GC using the described conditions. However, we notice that a mono- trans isomer of DHA, formed during both chemical and thermal treatments, co-elute with all- cis DHA. This feature should be taken into consideration for the quantification of DHA geometrical isomers.

Linear relationships in α,β-unsaturated carbonyl compounds between the half-wave reduction potentials, the frontier orbital energies and the Hammett σp values

A linear relationship between the half-wave reduction potentials of α,β-unsaturated carbonyl compounds R–CH CH–COX and the Hammett σ p values of R and X is proposed: E 1 / 2 = − 1.341 σ p ( X ) σ p ( R ) + 1.123 σ p ( X ) + 1.746 σ p ( R ) − 1.694 . A linear relationship is also observed for the LUMO's energy values, the absolute chemical hardness η, the chemical potential μ, the electrophilicity power ω, or the polarisation of the ethylenic double bond with the Hammett σ p values of R and X.

Functionalization of [60]fullerene through the anionic route

Abstract The reactivity of C602– anion, easily generated upon chemical reduction of the C60 core by sodium methanethiolate, has been systematically investigated versus a great number of saturated halogenated compounds RX or X–CH2–R′–CH2–X (X = I or Br), while these halo-compounds are unreactive with C60 itself. Various C60-derivatives in the series of bis-adducts R2C60 and fused cycloadducts R′(CH2)2C60 are thus obtained in fair to good yields, the R or R′ groups bearing functionalities such as ethylenic double bond, halogen, ketone, alcohol, or ester moieties. On the other hand a judicious utilization of the overall mechanism of the reaction between C602– anion and well chosen different RX and R′X compounds allow to extend this methodology to the preparation of mixed adducts RR′C60. Functional adducts in the series R2C60 and R′(CH2)2C60 are new attractive building blocks in C60 chemistry, and can lead to novel highly functionalized C60-based molecules. Some examples of such covalent ensembles are presented, the specific physical properties of which are typical of organic materials. To cite this article: J. Cousseau et al., C. R. Chimie 9 (2006).

Thermal degradation of long‐chain polyunsaturated fatty acids during deodorization of fish oil

Long-chain polyunsaturated fatty acids (LC-PUFA) of the n-3 series, particularly eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid, have specific activities especially in the functionality of the central nervous system. Due to the occurrence of numerous methylene-interrupted ethylenic double bonds, these fatty acids are very sensitive to air (oxygen) and temperature. Non-volatile degradation products, which include polymers, cyclic fatty acid monomers (CFAM) and geometrical isomers of EPA and DHA, were evaluated in fish oil samples obtained by deodorization under vacuum of semi-refined fish oil at 180, 220 and 250 °C. Polymers are the major degradation products generated at high deodorization temperatures, with 19.5% oligomers being formed in oil deodorized at 250 °C. A significant amount of CFAM was produced during deodorization at temperatures above or equal to 220 °C. In fact, 23.9 and 66.3 mg/g of C20 and C22 CFAM were found in samples deodorized at 220 and 250 °C, respectively. Only minor changes were observed in the EPA and DHA trans isomer content and composition after deodorization at 180 °C. At this temperature, the formation of polar compounds and CFAM was also low. However, the oil deodorized at 220 and 250 °C contained 4.2% and 7.6% geometrical isomers, respectively. Even after a deodorization at 250 °C, the majority of geometrical isomers were mono- and di-trans. These results indicate that deodorization of fish oils should be conducted at a maximal temperature of 180 °C. This temperature seems to be lower than the activation energy required for polymerization (intra and inter) and geometrical isomerization.

3-Nitrocinnamic acid

The title compound, $C_{9}H_{7}NO_{4}$, forms centrosymmetric dimers through intermolecular O-(HO)-O-... hydrogen bonds in the crystal structure.The nitro group deviates slightly from coplanarity with the benzene ring. The benzene ring and the carboxylic acid group are in an E configuration about the ethylenic double bond.

Initial Events in the Photocycle of Photoactive Yellow Protein

The light-induced isomerization of a double bond is the key event that allows the conversion of light energy into a structural change in photoactive proteins for many light-mediated biological processes, such as vision, photosynthesis, photomorphogenesis, and photo movement. Cofactors such as retinals, linear tetrapyrroles, and 4-hydroxy-cinnamic acid have been selected by nature that provide the essential double bond to transduce the light signal into a conformational change and eventually, a physiological response. Here we report the first events after light excitation of the latter chromophore, containing a single ethylene double bond, in a low temperature crystallographic study of the photoactive yellow protein. We measured experimental phases to overcome possible model bias, corrected for minimized radiation damage, and measured absorption spectra of crystals to analyze the photoproducts formed. The data show a mechanism for the light activation of photoactive yellow protein, where the energy to drive the remainder of the conformational changes is stored in a slightly strained but fully cis-chromophore configuration. In addition, our data indicate a role for backbone rearrangements during the very early structural events.

A Classical Approach to Aromaticity and a New Representation of Benzene

AbstractFor Abstract see ChemInform Abstract in Full Text.

A classical approach to aromaticity and a new representation of benzene

The classical chemical structure theory (CST) provides “localised” qualitative models for the structure and reactivity of organic molecules, while, in addition to quantitative methods, the modern molecular orbitals (MO) theory provides “delocalised” qualitative models. In particular, these two theories provide two different descriptions of the ethylenic double bond, bent bonds and σ/π orbitals, respectively. In the framework of CST, a graphical model of aromaticity and antiaromaticity, related to a classical model of Woodward–Hoffmann rules, is presented. By application of Linnett's double-quartet theory, a new representation for benzene is proposed. It can be easily visualised when a new split representation of Linnett-type formulae is used.

Absorption and Fluorescence Properties of Some Substituted 2‐Furylbenzothiazoles and Their Vinylogues in Various Solvents

Absorption and fluorescence emission spectra of six substituted 2‐(2‐furyl) benzothiazoles and their vinylogues have been studied in different solvents at room temperature. It was found that both the kind of the substituent and the solvent polarity influenced the spectral properties. The ethylenic double bond between the furyl and benzothiazolyl moiety caused a bathochromic shift in the longwave absorption maxima of 1927–3182 cm− 1 as well as a bathochromic shift in the fluorescence maxima of 2646–3338 cm− 1. For substituted 2‐(2‐furyl)benzothiazoles a linear relationship between solvent polarity and Stokes shift was observed. This group of compounds exhibited higher relative fluorescence quantum efficiency than their vinylogues. The most fluorescent compound among them was 2‐(5‐phenyl‐2‐furyl)benzothiazole.

A New Synthetic Approach for Novel 4‐Substituted‐5‐nitroimidazoles.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Isolation and characterization of a delta5 FA desaturase from Pythium irregulare by heterologous expression in Saccharomyces cerevisiae and oilseed crops.

By using the polymerase chain reaction approach with two degenerate primers targeting the heme-binding and the third histidine-rich motifs in microsomal carboxyl-directed desaturases, we identified a cDNA PiD5 from Pythium irregulare encoding a delta5 desaturase. The substrate specificity of the enzyme was studied in detail by expressing PiD5 in a yeast (Saccharomyces cerevisiae) mutant strain, AMY-2alpha, where ole1, a delta9 desaturase gene, is disrupted. The result revealed that the encoded enzyme could desaturate unsaturated FA from 16 to 20 carbons beginning with delta9 and delta11 as well as delta8 ethylenic double bonds. Introduction of PiD5 into Brassica juncea under the control of a CaMV 35S constitutive promoter resulted in accumulation of several delta5-unsaturated polymethylene-interrupted FA (delta5-UPIFA) including 18:2-5,9, 18:2-5,11, 18:3-5,9,12, and 18:4-5,9,12,15 in vegetative tissues. The transgenic enzyme could also desaturate the exogenously supplied homo-gamma-linolenic acid (20:3-8,11,14) to arachidonic acid (20:4-5,8,11,14). Introduction of PiD5 into B. juncea and flax under the control of seed-specific promoters resulted in production of delta5-UPIFA, representing more than 10% of the total FA in the seeds.

A new synthetic approach for novel 4-substituted-5-nitroimidazoles

A new synthetic approach, involving an S RN1 reaction of the anion of 1-methyl-4-phenylsulfonyl-methyl-5-nitro-1 H-imidazole with 2,2-dinitropropane and a radical anion or a concerted radical reductive elimination of sulfonyl and nitro groups affords an original 5-nitroimidazole bearing a trisubstituted ethylenic double bond at 4-position.