Olefinic Structure Research Articles

The Macromolecular Design of Poly(styrene-isoprene-styrene) (SIS) Copolymers Defines their Performance in Flexible Electrothermal Composite Heaters.

Electric cars are desirable for their environmental and economic benefits yet face limitations in range in cold weather due to the increased energy demands for cabin heating. To provide efficient heating for vehicles, flexible composite electrothermal heaters offer a viable solution owing to their lightweight design, efficiency, and adaptability for use within and beyond vehicle interiors. The current study aims to improve electrothermal heater stability and performance by understanding the impact of the polymer structure on composite properties. We explore how the presence and molecular structure of olefinic bonds within the polyisoprene block of styrenic triblock copolymers affect thermal stability and performance. Composite electrothermal heaters were fabricated by dispersing carbon black (CB) as the heating material in three triblock copolymer matrices, poly(styrene-1,4-isoprene-styrene) (1,4-SIS), poly(styrene-3,4-isoprene-styrene) (3,4-SIS), and its hydrogenated version poly(styrene-ethylene-propylene-styrene) (SEPS). The chemical structure and thermal properties of each copolymer were linked to electrothermal performance measurements of composite heaters to establish structure-function relationships. Notably, 3,4-SIS with 28 wt % CB demonstrated the highest thermal and electrical conductivity, resulting in uniform heat distribution. The outcomes unambiguously demonstrate that the olefinic structure of SIS copolymers enhances the electric and thermal conductivity, leading to enhanced electrothermal performance of prototype heaters compared to that of the hydrogenated copolymer.

Synthesis and photoinitiated cationic polymerization of epoxidized phenylpropanoid and α-pinene derivatives

Phenylpropanoides and myrtenol were converted into laurates in a first reaction step followed by epoxidation of the olefinic structure using m-chloroperbenzoic acid to synthesize new epoxy monomers. These are epoxy eugenyl laurate (EEL), epoxy isoeugenyl laurate (EiEL), epoxy cinnamyl laurate (ECL), and epoxy myrtenyl laurate (EML). Cationic photoinitiated polymerization of the new epoxy monomers melting below or slightly above room temperature results in oligomers with a degree of polymerization between 2 and 6. The low degree of polymerization causes a glass transition temperature of the new oligoethers below the polymerization temperature indicating the neglecting influence of vitrification on the photoinitiated polymerization of these epoxy monomers. Significant differences were found regarding the kinetics of the cationic photoinitiated polymerization between the single new epoxy monomers and epoxy anethol (EA) as well as epoxy estragol (EE). The molar polymerization enthalpy determined for epoxy monomers undergoing quantitative conversion differs from the value for ethylene oxide that is known from the literature. This indicates the influence of the substituents bound at the epoxy group on the polymerization kinetics.

Study on the formation of olefinic-bond-containing asphaltenes during thermal cracking of vacuum residue

In this study, the occurrence of olefinic bonds in asphaltenes separated from vacuum residue (VR) during thermal cracking was explored. Also, the effect of various thermal cracking conditions on the nature of olefinic bonds was discussed. The results showed that olefinic bonds were formed in asphaltenes during VR thermal cracking. The olefinic structure of asphaltenes detected by Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (1H NMR) spectroscopy was mainly in the type of R–CH = CH–R′. An in-depth investigation revealed that increasing the severity of thermal cracking promoted the formation of more olefinic-bond-containing asphaltenes; the percentage of olefinic hydrogen in asphaltenes peaked at cracking under 420 °C for 40 min, was 2.7%. Meanwhile, the olefinic-bond-containing asphaltenes of high concentration consequently became precursors for the formation of coke by increasing the instability of the liquid system. Consequently, further prolongation of the cracking time led to a drastic decline of olefins content accompanying a sharp leap of coke yield. Finally, the hypothetical average molecular structures of the olefinic-bond-containing asphaltenes during VR thermal cracking were proposed based on the modified Brown-Ladner empirical formulas with improvement. They serve as intuitive insights into the existing olefinic bonds in asphaltenes.

Contrasting Diastereoselectivity between Cyclic Nitrones and Azomethine Ylides. Stereocontrolled Pathways to cis-anti-anti-cis-Oxazatetraquinanes from a Bicyclic Nitrone.

A study of [3 + 2] cycloaddition reactions of a bicyclic nitrone with various cyclopentenes has clarified the diastereomeric preferences as a function of the olefinic structure. It has also identified an important stereochemical difference between nitrones and the analogous azomethine ylides in [3 + 2] cycloaddition reactions.

Na2SiO3‐Catalyzed Glycerolysis of Sacha Inchi (Plukenetia volubilis L.) Oil into Di‐ and Monoacylglycerols

AbstractDirect glycerolysis of novel edible Sacha Inchi (Plukenetia volubilis L.) seed oil (PvLO) into diacylglycerols (DAG) and monoacylglycerols (MAG) was studied over solid Na2SiO3 with or without microwave assistance. The glycerolysis yield was calculated by qualitative and semiquantitative analyses of 1H NMR, 13C NMR, and FT‐IR spectra. The yields of ~33% 1, 3‐DAG, ~16% 1, 2‐DAG, ~40% 1‐MAG, and ~2.3% 2‐MAG were achieved after 16 hours at 120 °C in three consecutive cycles using acetone, with an interesterification rate of 92%. The modified oil showed enhanced gelation ability at low temperatures. The yield of 1, 2‐DAG can be increased by adding acetone as solvent. The fatty acid compositions and unsaturated structure of lipids were less destroyed after alkaline glycerolysis. However, more α‐linolenic and linoleic acids were transferred to the sn‐2 position of glyceryl skeleton. The oxidative stability of the modified oil was still controllable. In summary, this work provides a feasible method to convert polyunsaturated plant oils into oils rich in DAG and MAG with less destructive impact on the olefinic structure of oil. Also, it provides a useful example of how to quickly evaluate the influence of chemical modification on the chemical structure of plant oils by using various spectral technologies.

Studies on the anti-oxidative ability of quinones in natural ester based insulating liquids for transformers

Due to the unsaturated olefinic structure of natural esters, their antioxidation ability is generally poorer than that of the mineral oils, thus certain antioxidants were commonly added as the additives to improve the oxidative stability of natural ester for their service as transformer oils. The present study reported the influences of adding quinones as additives on the oxidative stability of versatile natural esters. It was found that, under the accelerated oxidation conditions, added quinones could improve the oxidative stability of these tested natural esters through decreasing their acidic values, viscosity increase and dielectric losses to certain extent, thus providing a new category of antioxidants to improve the oxidative stability of natural ester based transformer oils.

Ring-expansion approach towards extended asymmetric benzopentafulvalenes: overcrowded olefinic structure and chain length-dependent properties

A strain energy-induced ring-expansion is described to construct novel asymmetric benzopentafulvalenes precisely, which show chain length-dependent physical properties and air-stable ambipolar carrier transport.

Effects of coating pressure on the thermal and mechanical properties of glow discharge polymer films

The glow discharge polymer (GDP) films for laser fusion targets were successfully fabricated by plasma polymerization technology at different coating pressures. The chemical structure of GDP films was characterized by the Fourier transform infrared (FT-IR) spectrum. The thermal stability was evaluated by thermal-gravimetric analysis (TGA). The mechanical properties were measured by nano-indentation technology. The thickness of GDP films was measured by profile meter. The results show that the deposition rate of GDP films increases with increasing coating pressure. The olefinic structure, the ratio of carbon/hydrogen, and the content of C C in GDP films increase as the pressure increases. At the lower coating pressure, the thermal stability, hardness and Young's modulus of GDP films were well. By calculation, the buckle strength of the GDP films can meet the ICF experiments.

Influence of RF power on the structure and properties of glow discharge polymer

Using trans-2-butene and hydrogen as the precursor, the glow discharge polymer films was successfully coated on KBr discs by glow discharge polymerization at different powers. The chemical structure, thermal stability of the GDP films and the deposition rate of GDP films were characterized by the FT-IR, TG and surface profiler technology. The Results show that the deposition rate, the olefinic structure, the ratio of C/H, and the content of C C in GDP films increase with the RF power increasing. The thermal stability of GDP films fabricated at higher RF power is better.

DFT Calculation on the Stereochemistry of the Allylic Oxidation. Selenium Dioxide-Mediated Oxidation of an Exocyclic Olefinic Hydrindane Compound

Selenium dioxide-mediated oxidation is among the most important transformations for introducing an hydroxy group into the allylic position in the substituted alkenes in organic and biochemical pathways. A unique mode of highly stereoselective interaction of selenium dioxide with olefins, resulting in allylic alcohols, is well exemplified for the preparation of a steroid compound as shown Scheme 1. Since Sharpless and Lauer proposed a mechanism, generally accepted, for this process in 1972 as resulting from an initial ene reaction followed by a [2,3]-sigmatropic rearrangement, there have been considerable efforts on particularly clarifying the stereo-selectivity of this reaction. For example, Singleton and Hang clarified a concerted aspect of the ene step in the allylic oxidation of 2-methyl-2-butene with selenium dioxide (1 → 2 in Scheme 2). Recently we have elucidated the overall pathways in detail by treating theoretically both an ‘ene’ reaction and the 2,3-sigmatropic rearrangement involved in this selenium dioxide-mediated oxidation of 1: the allylic oxidation occurs by complex mechanisms via two competing paths such as anti-approach and syn-approach in the ‘ene’ reaction to produce the (E)allylic alcohol 2, where it has been first noticed the Cα-Cβ bond rotation in 2,3-rearrangement step plays an important part for the stereo-selectivity of the reaction. Now our attention is brought to understand the consequence of the Cα-Cβ bond rotation in the selenic acid intermediate produced from the ene step as to whether it may affects the stereochemical course of the allylic oxidation of a hydrindane compound 5, where an exocyclic olefinic structure is crafted (Scheme 3). Here, we report the results of ab initio studies of the allylic oxidation of 5, focusing on analyzing whether the conformational change via bond rotation in selenic acid intermediate 6 may give rise to produce 9. To study the reaction pathway with relative stabilities for possible transition states during the allylic oxidation of model compound 5 (Scheme 4 and Table 1), we have investigated the energy of possible transition states in SeO2 oxidation of 5 by b3lyp/6-31G* calculation. In ene reaction step, the anti approach of selenium dioxide is energetically favored than the syn one by 1.82 kcal/mol (entry 2 and 3 in Table 1). In the following 1,3-rearrangement step, the O=Segroup approach to the α face of double bond is more favorable than the β face by 2.28 kcal/mol (entry 4 and 5 in Table 1). The compound 7 as a major product should be obtained by the pathway of ts-1a and ts-1a-2α. The other isomer 9 can be formed through the pathway of ts-1a and ts1a-2β, where a Cα-Cβ bond rotation of the ‘ene’ reaction

Thermally stable oxadiazole-containing polyacetylenes: Relationship between molecular structure and nonlinear optical properties

Two novel high molecular weight functional polyacetylenes bearing oxadiazole groups as pendants, poly(2-(4-decyloxyphenyl)-5-(4-ethynylphenyl)-1, 3, 4-oxadiazole) (P1) and poly(2-(4-butyloxyphenyl)-5-(4-ethynylphenyl)-1, 3, 4-oxadiazole) (P2) were designed and synthesized by a multistep reaction route. The structures and properties were characterized and evaluated with FTIR, NMR, UV, TGA, GPC, optical-limiting (OL) and nonlinear optical (NLO) analyses. The incorporation of oxadiazole into polyacetylene significantly endows polyacetylenes with higher thermal stability and optical limiting property. The solubility, stereoregularity and optical properties of resultant polyacetylenes are obviously affected by flexible terminal alkoxy chain length. The cis olefinic structure content in polyacetylene backbone increases with increasing terminal alkoxy group length. The functional polyacetylene with the higher cis olefinic structure content shows higher thermal stability, better optical limiting property and larger third-order nonlinear optical performance. The optical limiting mechanism of resulting polymers was investigated, which is mainly originated from larger excitation state absorption cross-section of molecules to result in reverse saturable absorption.

Photodegradation Chemistry of the Insecticide Phosmet in Lipid Models and in the Presence of Wool Wax, Employing a 15N-Labeled Compound

The organophosphorus insecticide phosmet is commonly used for plant protection as well as against pests on animals. Phosmet features numerous degradation pathways induced by UV irradiation. In this study, we focused on the reaction possibilities of phosmet in the presence of lipophilic substances with olefinic structure elements, as they are frequently found in animal fur lipids, especially in wool wax. In the first step, simple models were employed to characterize the structural types of formed photoaddition products. On irradiation in the presence of cyclohexene, three photoaddition products were identified, a (4pi + 2pi) cycloaddition product of phosmet and cyclohexene and two diastereoisomer carbinols. Likewise, in more sophisticated models employing fatty acid methyl esters for irradiation experiments, phosmet was readily photodegraded. In the presence of methyl oleate, also 1:1 photoaddition products could easily be identified by means of liquid chromatography-mass spectrometry, using a stable isotope-labeled phosmet (15N-phosmet, 50 at. %) for the photolysis experiments. To converge from models to the more complex natural environment of animal skin lipids, irradiation experiments of phosmet in the presence of wool wax were performed. After 24 h of irradiation, only a remnant of 1.4% of the initial phosmet was detectable. Phosmet-oxon was detected in concentrations up to 27.3 mol %.

5′-Noraristeromycin possessing a C-1′ cyclopentyl double bond: a new carbanucleoside structural prototype

Prior to this work only two examples of carbanucleosides possessing a C-1′/C-6′ double bond had been reported and they were minor derivatized side products arising during other targeted syntheses. To develop this structural feature into a new class of potential antiviral agents, the 5′-nor derivative of aristeromycin with such an olefinic structure ( 6 ) represents the first example. In this regard, treatment of (1′ S,2′ S,3′ S,4′ R,5′ S)-6-chloro-9-(2′,3′- isopropylidenedioxy-6′-oxabicyclo[3.1.0]hex-4′-yl)purine ( 7 ) with sodium methoxide yielded 6 via an E′ 2-like elimination pathway. A convenient way to the C-4′ epimer of 6 (that is, 17 ) also arose during these studies and is described. Antiviral analysis of 6 and 17 failed to produce any significant activity.

Composition and Structural Studies of Strong Glow Discharge Polymer Coatings

An investigation of the chemical composition and structure of strong glow discharge (GDP) polymer shells made for cryogenic experiments at OMEGA is described. The investigation was carried out using combustion and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The strongest coatings were observed to have the lowest hydrogen content or hydrogen/carbon H/C ratio, whereas the weakest coatings had the highest hydrogen content or H/C ratio. Chemical composition results from combustion were used to complement FTIR analysis to determine the relative hydrogen content of as-fabricated coatings. Good agreement was observed between composition results obtained from combustion and FTIR analysis. FTIR analysis of coating structures showed the strongest coatings to have less terminal methyl groups and a more double bond or olefinic structure. Strong GDP coatings that were aged in air react more with oxygen and moisture than standard GDP coatings. In addition to a more olefinic structure, there may also be more free-radical sites present in strong GDP coatings, which leads to greater oxygen uptake.

Exploring the Boundary between Aromatic and Olefinic Character: Bad News for Second-Order Perturbation Theory and Density Functional Schemes

The question whether [10]annulene prefers olefinic structures with alternate single and double bonds or aromatic structures like all other small to medium sized uncharged (4n + 2){pi} electron homologs (e.g. benzene, [14]annulene) has been controversial for more than 20 years. Our new results suggest that only the high-order correlated methods will be able to correctly predict the [10]annulene potential energy surface. The UNO-CAS results and the strong oscillation of the MP series show that nondynamical electron correlation is important. Consequently, reliable results can only be expected at the highest correlated levels like CCSD(T) method, which predicts the olefinic twist structure to be lower in energy by 3-7 kcal/mol. This prediction that the twist structure is lower in energy is supported by (a) the MP2-R12 method, which shows that large basis sets favor the olefinic structure relative to the aromatic, and (b) the fact that both structures are about equally affected by nondynamical electron correlation. We conclude that [10]annulene is a system which cannot be described adequately by either second-order Moller-Plesset perturbation theory or density functional methods. 13 refs., 3 tabs.

Conformation of cyclic peptides. Principle concepts and the design of selectivity and superactivity in bioactive sequences by 'spatial screening'

Abstract

An infrared spectroscopy study of 1-butene and its isomers adsorbed onto 12-tungstophosphoric acidSiO2

Abstract The infrared spectra of species formed from the adsorption of 1-butene, cis -2-butene and isobutene on 12-tungstophosphoric acid (H 3 PW 12 O 40 ) show primarily saturated CC bonds and little or no evidence of the olefinic structure. The 2960 cm −1 band, attributed to asymmetric CH 3 stretching is the most prominent band with all three of the isomers. The infrared spectra of the isomers show evidence of the polymerization of butene on the surface of the catalyst. The intensities of the 2960, 2933 and 2875 cm −1 bands observed in the spectra of 1-butene essentially vanished on evacuation at 300°C but the band at 1590 cm −1 attributed to conventional coking remained largely intact under the same conditions.

A comparative study of products derived from Rundle and Stuart shale oils and petroleum lubricating oil base stocks (based on n.m.r., molecular weight and elemental analysis)

As part of a study to evaluate the potential of shale oils for lubricating oil production, samples from the Rundle and Stuart oil shale deposits in Australia have been processed to produce a range of products which were then characterized by 1H and 13C high resolution nuclear magnetic resonance (n.m.r.) techniques, molecular weight determination and elemental analysis. The data have been compared with that obtained for two petroleum derived lubricating oil base stock samples. The comparison shows that the products derived from Rundle and Stuart shale oils in the lubricating oil boiling range have lower molecular weight and a lower hydrogen content. The lubricating oil samples are shown to contain monoaromatic rings, with one or more branched, long, alkyl side chains per ring, some naphthenic but no olefinic structure. The shale oil samples show distinct differences, with the distillate being monoaromatic with some polyaromatic and naphthenic structures, but with less alkyl substitution. The alkyl side chains are unbranched and contain some olefinic bonds. The maltenes are in turn less substituted and have less naphthenic structure. The alkylation and dewaxing processing steps did not significantly modify the structures of the shale oil products, while in the hydrogenation process some of the olefinic material was modified to paraffinic. Further reduction of the aromatic content of the shale oil is required to improve the prospects of producing a lubricating oil base stock.

Hydrogen-atom attack on 1-phenylpropene at high temperatures

The reactions of hydrogen atom with 1-phenylpropene (IPP) have been studied in single-pulse shocktubeexperiments. Contribution from a large number of the possible reactive channels has been observed. The prime channels are the displacement of the methyl group resulting from addition to the olefinic structure and abstraction of a hydrogen from the methyl group followed by internal displacement of the hydrogen, forming indene. Displacement from the ring is less favored. The following rate expressions at temperatures of 990–1100 K and pressures of 1.4–2.0 atm have been determined. k ( H + 1 − p h e n y l p r o p e n e → s t y r e n e + m e t h y l ) = 10 13.6 ± 0.5 exp ⁡ ( − 1200 ± 1000 / T ) k ( H + 1 − p h e n y l p r o p e n e → p r o p e n e + p h e n y l ) = 10 14.0 ± 0.7 exp ⁡ ( − 5300 ± 1500 / T ) k ( H + 1 − p h e n y l p r o p e n e → p r o p e n y l + b e n z e n e ) = 10 14.2 ± 0.7 exp ⁡ ( − 6300 ± 1500 / T ) k ( H + 1 − p h e n y l p r o p e n e → 3 − p h e n y l a l l y l + H 2 + H 2 ) ⩽ 10 14.2 ± 0.5 exp ⁡ ( − 5600 ± 1000 / T ) , where the relative and absolute uncertainties in the rate constants are factors of 1.10 and 1.25, respectively. An attempt has been made to relate these rate expressions to basic thermal processes, and similarities to those for the appropriate smaller olefins have been noted. Displacement rate constants are made smaller by the reversibility of the hydrogen addition reaction, and together with possible isomerizations, they represent an additional complicating feature

Ultraviolet-light irradiation of a radio-frequency plasma applied to fluoropolymer sputtering deposition

The excited states of molecular species in plasma play an important role in the organic film deposition process. The film structure and its characteristics are very dependent on this film preparation process. Although plasma species are in an excited transition state to spontaneously decompose and react easily with relatively stable molecules, they are not excited to the electronic transition state sufficiently to dissociate into multivalenced carbon species and polymerized into a polyolefinic film. In this research, ultraviolet-light irradiation is used during radio-frequency fluoropolymer sputtering as an excitation source to enhance the dissociation of molecular species in plasma. The film obtained has an olefin and cross-linking rich structure. The effects of this process on the film structure and its lubricating characteristics are examined. The plasma-emission analysis and mass spectroscopy showed that the bond dissociation of the sputtered segments has been stimulated by this photoassisted process. Consequently, the number of C■C bonds in the film obtained from photoassisted sputtering has increased in comparison with a film obtained from conventional sputtering, as observed by IR and XPS analyses. The resistance of the film to Ar ion bombardment was enhanced by the photoassisted sputtering. The film obtained from polychlorotrifluoroethylene (PCTFE) sputtered in CF4 had an extremely long lubrication life due to an increase in the rigid olefinic structure.