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Wax esters play critical roles in biological systems, serving functions from energy storage to chemical signaling. Their diversity is attributed to variations in alcohol and acyl chains, including their length, branching, and the stereochemistry of double bonds. Traditional analysis by mass spectrometry with collisional activations (CID, HCD) offers insights into acyl chain lengths and unsaturation level. Still, it falls short in pinpointing more nuanced structural features like the position of double bonds. As a solution, this study explores the application of 213-nm ultraviolet photodissociation (UVPD) for the detailed structural analysis of wax esters. It is shown that lithium adducts provide unique fragments as a result of Norrish and Norrish-Yang reactions at the ester moieties and photoinduced cleavages of double bonds. The product ions are useful for determining chain lengths and localizing double bonds. UVPD spectra of various wax esters are presented systematically, and the effect of activation time is discussed. The applicability of tandem mass spectrometry with UVPD is demonstrated for wax esters from natural sources. The UHPLC analysis of jojoba oil proves the compatibility of MS2 UVPD with the chromatography time scale, and a direct infusion is used to analyze wax esters from vernix caseosa. Data shows the potential of UVPD and its combination with CID or HCD in advancing our understanding of wax ester structures. [ABSTRACT FROM AUTHOR]

Fatty acids (FAs) contain a vast amount of structural diversity, and differences in fatty acid structure have been associated with various disease states. Accurate identification and characterization of fatty acids is critical to fully understand the biochemical roles these compounds play in disease progression. Conventional tandem mass spectrometry (MS/MS) workflows do not provide sufficient structural information, necessitating alternative dissociation methods. Gas‐phase charge inversion ion/ion reactions can be used to alter the ion type subjected to activation to provide improved or complementary structural information. Herein, we have used an ion/ion reaction between fatty acid (FA) anions and magnesium tris‐phenanthroline [Mg(Phen)3] dications to promote charge remote fragmentation of carbon‐carbon bonds along the fatty acid chain, allowing for localization of carbon‐carbon double bond (C=C) positions to successfully differentiate monounsaturated fatty acid isomers. Relative quantification was also performed to obtain the relative abundance of fatty acid isomers in different biological tissues. For example, the relative abundance of FA 18 : 1 (9) was determined to vary across regions of rat brain, rat kidney, and mouse pancreas, and FA 16 : 1 (9) was found to have a higher relative abundance in the dermis layer compared to the sebaceous glands in human skin tissue. [ABSTRACT FROM AUTHOR]

A series of nematic liquid crystal (LC) monomers, containing a reactive group in the lateral substituent, were designed and synthesised through an organic synthesis reaction. Considerable changes were made to the properties of the liquid monomers by varying the terminal alkyl chain lengths. The molecular structures of the intermediates and the LC monomers were characterised by flourier infrared absorption spectrometry and proton nuclear magnetic resonance (1H NMR) spectroscopy, leading to the identification of the target product. The phase transition temperatures of the LC monomers were observed and analysed using differential scanning calorimetry (DSC) and polarising optical microscopy (POM) with a hot stage. The two-way thermotropic liquid crystalline behaviour was observed during the heating process, providing insight into the effect of substituent changes on the phase transition temperature. [ABSTRACT FROM AUTHOR]

The tetrasilyl‐substituted distannene, (tBu2HSi)2Sn=Sn(SiHtBu2)26, was synthesized by mild thermolysis (70 °C in hexane) of tris(di‐tert‐butyl‐hydridosilyl)stannane 4. The X‐ray crystallography structure of 6 reveals the following unusual structural properties: a planar geometry around both Sn atoms (Σ∡Sn=359.87°), a non‐twisted Sn=Sn double bond, and the shortest Sn=Sn double bond of 2.599 Å among all acyclic distannenes. Thus, compound 6 is the first reported distannene having a structure closely analogous to a classic alkene. Reactions of 6 with CCl4 or with 2,3‐dimethylbuta‐1,3‐diene to produce 1,2‐dichlorodistannane 9 and the [2+4] cycloadduct 10, respectively, are characteristic for a Sn=Sn double bond. [ABSTRACT FROM AUTHOR]

This article presents a new method for synthesizing allenes, a class of organic compounds with a unique structure. The method involves using methylthioalkynes as precursors to alkylidene carbenoids, which are then combined with other compounds to form the desired allenes. The authors discuss the experimental conditions and improvements made to the process to enhance efficiency and control over the stereochemistry of the products. However, they also acknowledge that further research is necessary to fully comprehend the mechanism and enhance the results. [Extracted from the article]

To study the effect of fatty acid unsaturation on low-rank coal flotation, oleic acid, linoleic acid, and linolenic acid with the same number of carbon atoms but an increasing number of double bonds were selected as flotation collectors and compared with conventional nonpolar collector diesel oil. Adhesion force measurements between particles and bubbles and molecular dynamics simulation of reagent adsorption were used to reveal the mechanism of unsaturated fatty acids enhancing low-rank coal flotation. The flotation results show that unsaturated fatty acid collectors surpass nonpolar diesel oil in flotation performance, and the flotation yield of low-rank coal increases with fatty acid unsaturation. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to analyze the surface morphology and surface functional groups of low-rank coal. SEM results show that the surface of low-rank coal is loose and contains many pores and cracks, which is not conducive to the spreading of chemicals on coal surfaces and the mineralization of bubbles and particles. The results of FTIR and XPS show that the surface of low-rank coal contains several oxygen-containing functional groups and has poor hydrophobicity, resulting in low flotation recovery. The adhesion force between bubbles and coal surfaces was measured in different collector solutions. The maximum adhesion between bubbles and coal surfaces increased with collector unsaturation in diesel oil, oleic acid, linoleic acid, and linolenic acid systems, indicating an increase in the floatability of coal particles with collector unsaturation. Furthermore, the molecular dynamics simulation of unsaturated fatty acid adsorption showed that unsaturated fatty acids spread on coal surfaces through hydrogen bonding between the polar groups of these molecules and surfaces. With an increasing number of double bonds, unsaturated fatty acids become more polar, and the spread of unsaturated fatty acids on coal surfaces gradually becomes more extensive, which leads to increasing particle floatability. This is the main reason for the increase in flotation recovery of low-rank coal with unsaturated fatty acids.

A facile synthesis for unprecedented stibastannene (10) featuring a Sn=Sb‐double bond together with the homologous arsa‐ (9) and phosphastannenes (8) is presented. Chloride abstraction from respective stannyl pnictinidenes [E=P (5), As (6), Sb (7)], which were made accessible by reduction of ECl3 addition products at an intramolecular phosphine‐stabilized stannylene, gave the pnictastannenes in moderate yields. The pnictastannenes coordinate Pd(PPh3)2 fragments (12–14) and the phosphastannene forms also a nickel coordination compound with the Ni(PPh3)2‐fragment (11). 2,3‐Dimethylbutadiene shows a [2+4]‐cycloaddition (15–17) in reaction with the pnictastannenes (8–10). Products of a [2+2]‐addition (18, 19) were isolated as the phosphaalkyne reaction products for 8 and 9. Addition of an O−H bond at the Sn=P‐bond was found in reaction of water with phosphastannene 8. Reaction with ammonia afforded the NH3‐adducts (21–23) at the tin atom for pnictastannenes 8–10. Only in the case of the arsastannene an azide reaction product featuring a three membered Sn−As−N‐ring was obtained. [ABSTRACT FROM AUTHOR]

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In this review, the latest achievements in the field of multiply bonded organogermanium derivatives, mostly reported within the last two decades, are presented. The isolable Ge-containing analogues of alkenes, alkynes, 1,3-dienes, allenes, and vinylidenes are discussed, and for each class of unsaturated organogermanium compounds, the most representative examples are given. The synthetic approaches toward homonuclear multiply bonded combinations solely consisting of germanium atoms, and their heteronuclear variants containing germanium and other group 14 elements, both acyclic and cyclic, are discussed. The peculiar structural features and nonclassical bonding nature of the abovementioned compounds are discussed based on their spectroscopic and structural characteristics, in particular their crystallographic parameters (double bond length, trans-bending at the doubly bonded centers, and twisting about the double bond). The prospects for the practical use of the title compounds in synthetic and catalytic fields are also briefly discussed. [ABSTRACT FROM AUTHOR]

The widely used alkyd resin suffers not only the flammability but also the autoignition of resin waste. Its autoignition should result from the air-drying exothermic effect due to autoxidation and conversion of double bond. However, the air-drying exothermic effect is seldom studied. In this study, five soybean oil-based alkyd resins were synthesized. The content of double bond measured by the titration method increased linearly with increasing the molar fraction of maleic anhydride. After air-drying, the infrared spectroscopy absorption peak for the double bond disappeared. Considering that the curing originated from the conversion of chemical bonds, the exothermic effect was theoretically analyzed to be 1163–1455 kJ mol−1 double bond based on the air-drying mechanisms and the differences among chemical bond energies. According to thermodynamics principles, the air-drying exothermic effect was also derived from the measured heat of combustion. When the content of double bond increased from 2.19 mol kg−1 resin to 2.56 mol kg−1 resin, the exothermic effect linearly increased from 1352 kJ mol−1 double bond or 2.96 kJ g−1 resin to 2508 kJ mol−1 double bond or 6.42 kJ g−1 resin. The steady and unsteady autoignition theoretical analyses implied that due to the air-drying exothermic effect the alkyd resin waste with a certain thickness would catch fire within one working day. [ABSTRACT FROM AUTHOR]

The design of porphyrin-based dendrimers featuring conjugated fluorenyl dendrons via alkene spacers allows evaluating the importance of the role of these spacers on the optical properties of interest. In the continuation of previous studies, a second-generation porphyrin-based dendrimer was synthesized and metalated by Zn(II) along with its known first-generation homologue. The targeted free-base porphyrin was obtained by repetitively cycling a Michaelis–Arbuzov reaction and a Horner–Wadsworth–Emmons reaction to construct the desired vinyl-containing dendrons. After metalation by Zn(II), meso-tetraphenylporphyrin-cored dendrimers with eight (ZnTPP-D1) and sixteen (ZnTPP-D2) fluorenyl arms at their periphery were eventually isolated. These species allow evaluating the influence of the central metal and of the 1,2-alkyne for 1,2-alkene exchange on fluorescence, oxygen photosensitization, and two-photon absorption. Such structure–property relationships are currently needed for the design of optimal dendrimeric photosensitizers allowing combined two-photon-based photodynamic therapy (2P-PDT) and imaging.

In this review, the latest achievements in the field of multiply bonded organogermanium derivatives, mostly reported within the last two decades, are presented. The isolable Ge-containing analogues of alkenes, alkynes, 1,3-dienes, allenes, and vinylidenes are discussed, and for each class of unsaturated organogermanium compounds, the most representative examples are given. The synthetic approaches toward homonuclear multiply bonded combinations solely consisting of germanium atoms, and their heteronuclear variants containing germanium and other group 14 elements, both acyclic and cyclic, are discussed. The peculiar structural features and nonclassical bonding nature of the abovementioned compounds are discussed based on their spectroscopic and structural characteristics, in particular their crystallographic parameters (double bond length, trans-bending at the doubly bonded centers, and twisting about the double bond). The prospects for the practical use of the title compounds in synthetic and catalytic fields are also briefly discussed.

Aureispira marina is a marine bacterium with gliding motility isolated from the southern coastline of Thailand. It contained ceramide as a major cellular lipid composed of saturated or unsaturated branched chain 2-hydroxy-fatty acid and sphingosine. The structure of unsaturated 2-hydroxy-fatty acid was investigated in our previous study, but the geometric configuration of the double bond remained unclear. In the present study, 14-methyl-∆ 2 -pentadecenol (∆ 2 -iso-C 16:1 -ol) was prepared from D-2-hydroxy-15-methyl-∆ 3 -hexadecenoic acid (D-2-OH-∆ 3 -iso-C 17:1 ) of the ceramide component, and analyzed by 1 H and 13 C NMR in comparison with ∆ 2 -trans-hexadecenol (∆ 2 -trans-n-C 16:1 -ol) derived from commercially available D-sphingosine. From the coupling constants of protons in the double bond and the chemical shift value of allylic carbon, the configuration of the double bond was determined as trans. Since the structure of 2-hydroxy-fatty acids was clarified, cellular fatty acids of A. marina and A. maritima, another species of the genus Aureispira, were reexamined, and the description on the cellular fatty acid composition of the genus Aureispira in the previous papers (Hosoya et al., 2006, Int. J. System. Evol. Microbiol., 56, 2931-2935; Hosoya et al., 2007, Int. J. System. Evol. Microbiol., 57, 1948-1951) lacking the description of 2-hydroxy-fatty acids was emended.

The design of porphyrin-based dendrimers featuring conjugated fluorenyl dendrons via alkene spacers allows evaluating the importance of the role of these spacers on the optical properties of interest. In the continuation of previous studies, a second-generation porphyrin-based dendrimer was synthesized and metalated by Zn(II) along with its known first-generation homologue. The targeted free-base porphyrin was obtained by repetitively cycling a Michaelis--Arbuzov reaction and a Horner--Wadsworth--Emmons reaction to construct the desired vinyl-containing dendrons. After metalation by Zn(II), meso-tetraphenylporphyrin-cored dendrimers with eight (ZnTPP-D1) and sixteen (ZnTPP-D2) fluorenyl arms at their periphery were eventually isolated. These species allow evaluating the influence of the central metal and of the 1,2-alkyne for 1,2-alkene exchange on fluorescence, oxygen photosensitization, and two-photon absorption. Such structure--property relationships are currently needed for the design of optimal dendrimeric photosensitizers allowing combined two-photon-based photodynamic therapy (2P-PDT) and imaging. [ABSTRACT FROM AUTHOR]

In the present investigation, 48 new tertiary amine derivatives of cinnamic acid, phenylpropionic acid, sorbic acid and hexanoic acid (4d–6g, 10d–12g, 16d–18g and 22d–24g) were designed, synthesized and evaluated for the effect on AChE and BChE in vitro. The results revealed that the alteration of aminoalkyl types and substituted positions markedly influences the effects in inhibiting AChE. Almost of all cinnamic acid derivatives had the most potent inhibitory activity than that of other acid derivatives with the same aminoalkyl side chain. Unsaturated bond and benzene ring in cinnamic acid scaffold seems important for the inhibitory activity against AChE. Among them, compound 6g revealed the most potent AChE inhibitory activity (IC50 value: 3.64 µmol/L) and highest selectivity over BChE (ratio: 28.6). Enzyme kinetic study showed that it present a mixed-type inhibition against AChE. The molecular docking study suggested that it can bind with the catalytic site and peripheral site of AChE.

The topic of heavier main group compounds possessing multiple bonds is the subject of momentous interest in modern organometallic chemistry. Importantly, there is an excitement involving the discovery of unprecedented compounds with unique bonding modes. The research in this area is still expanding, particularly the reactivity aspects of these compounds. This article aims to describe the overall developments reported on the stable derivatives of silicon and germanium involved in multiple bond formation with other group 13, and heavier groups 14, 15, and 16 elements. The synthetic strategies, structural features, and their reactivity towards different nucleophiles, unsaturated organic substrates, and in small molecule activation are discussed. Further, their physical and chemical properties are described based on their spectroscopic and theoretical studies. [ABSTRACT FROM AUTHOR]

Linear polyester ether was prepared at room temperature by Michael polymerization of hydroxyl and double bond using phosphazene-bases as catalyst, 2-methyl-1,3-propanediol and diacrylate as monomers. The effects of catalyst type, catalyst concentration, feed ratio of monomer and monomer type of double bond on polymerization reaction were investigated. The polymer structure and polymer reaction mechanism were studied by fourier transform-infrared spectroscopy（FT-IR） and nuclear magnetic resonance（NMR）, and the molecular weight and molecular weight distribution of the prepared polymers were characterized by size-exclusion chromatography（SEC）. The results show that the relatively higher molecular weight of polymer was prepared by phosphazene-bases t-BuP2 with appropriate concentration. In addition, increasing the carbon chain length of double bond monomer or improving the molar ratio of diacrylate to alcohol hydroxyl monomer can reduce the interesterification side reaction, and obtain higher molecular weight linear polymers. [ABSTRACT FROM AUTHOR]

Local nature of the boron-nitrogen (BN) bonding with different formal multiplicities (B≡N, B=N, B-N) have been investigated for 25 experimentally established organoboron molecules in both real and the Hilbert space, using topological analysis of electron localization function (ELF), electron density (AIM), and natural bond orbital (NBO) method. Each BN bond has been represented (ELF) by the bonding disynaptic attractor V(B,N), with the basin electron population between 5.72e and 1.83e, confirming possible existence of all the three bond types. A covalent character of bonding can be associated with the dative mechanism due to the V(B,N) bonding basin formed mainly (91–96%) by the N electron density. Similarly, the NBO method shows 2-center natural orbitals, consisting largely of the hybrids from the N atom. The AIM analysis yields the features typical for shared (H(3,−1)(r) < 0) and closed-shell (∇2ρ(3,−1)(r) > 0) interactions. The delocalization indices, describing electron exchanges between B and N quantum atoms, are smaller than 1.5, even for formally very short triple B≡N bonds. [ABSTRACT FROM AUTHOR]

Biodiesel is a notable alternative to petroleum derived diesel fuel because it comes from natural domestic sources and thus reduces dependence on diminishing petroleum fuel from foreign sources, it likely lowers lifecycle greenhouse gas emissions, and it lowers an engine’s emission of most pollutants as compared to petroleum derived diesel. However, the use of biodiesel often slightly increases a diesel engine’s emission of smog forming nitrogen oxides (NOx) relative to petroleum diesel. In this paper, previously proposed theories for this slight NOx increase are reviewed, including theories based on biodiesel’s cetane number, which leads to differing amounts of charge preheating, and theories based on the fuel’s bulk modulus, which affects injection timing. This paper proposes an additional theory for the slight NOx increase of biodiesel. Biodiesel typically contains more double bonded molecules than petroleum derived diesel. These double bonded molecules have a slightly higher adiabatic flame temperature, which leads to the increase in NOx production for biodiesel. Our theory was verified using numerical simulations to show a NOx increase, due to the double bonded molecules, that is consistent with observation. Further, the details of these numerical simulations show that NOx is predominantly due to the Zeldovich mechanism.

The average oil recovery by conventional water flooding from oil-wet and naturally fractured carbonate reservoirs is often less than 30%. Removal of adsorbed acidic components and/or asphaltene from the carbonate surface results in wettability alteration towards water-wet which is an effective approach to enhance oil recovery. Long chain fatty acids, long chain naphthenic acids and asphaltene are major components in crude oil which are responsible for wettability alteration in carbonate reservoirs while unsaturated acids have minor effect. In this study, a more accurate quantification of the effects of different types and structures of polar components that contribute to the initial oil-wetting extent of the reservoir rocks were used (aliphatic saturated acids, aliphatic unsaturated acids, naphthenic acids, aromatic acids and asphaltene). Different analytical tools (contact angle, zeta potential, Fourier transform infrared spectroscopy and thermal analysis) were utilized for all acids in order to study surface characteristics. The results indicated that polar organic compounds act in different ways according to their structure and properties. Presence of double bond could make the acid molecule more polar, reactive and less hydrophobic. In addition, it can affect the spatial arrangement of the molecule and hence its orientation on the surface. Presence of benzene ring increases the reactivity and polarity of carboxylic group. Moreover, it enhances hydrophilic properties of the acid due to electrons of π double bonds that can resonate over aromatic carbon atoms. The results revealed that, in the presence of water film, combination of acid dissociation in water, surface activity of acid and water solubility controls the acid adsorption and hence wettability alteration of the surface during aging process. Chemisorption of carboxylic acids/asphaltene changes the wettability of calcite surface. In addition to chemical adsorption, some acids adsorb physically on the surface. Physical adsorption of polar compounds may happen via hydrogen bonding between carboxylic groups and carbonate ions on the surface. Although physical adsorption is reversible and forms weak bonds between adsorbate and adsorbent, it may partially contribute to wettability alteration. • Polar organic compound act with calcite according to its structure and properties. • Double bond make the acid molecule more polar, reactive and less hydrophobic. • Presence of benzene ring increases the reactivity and polarity of carboxylic group. • Acid dissociation, surface activity and water solubility of acid control wettability. • Asphaltene adsorbed horizontally while carboxylic acids vertically on calcite. [ABSTRACT FROM AUTHOR]

The first divinyldiarsenes [{(NHC)C(Ph)}As]2 (NHC=IPr 3 a, SIPr 3 b; IPr=C{(NAr)CH}2; SIPr=C{(NAr)CH2}2; Ar=2,6‐iPr2C6H3) are reported. Compounds 3 a and 3 b were prepared by the reduction of corresponding chlorides {(NHC)C(Ph)}AsCl2 (NHC=IPr 2 a, SIPr 2 b) with Mg. Calculations revealed a small HOMO–LUMO energy gap of 3.86 (3 a) and 4.24 eV (3 b). Treatment of 3 a with (Me2S)AuCl led to the cleavage of the As=As bond to restore 2 a, which is expected to proceed via the diarsane [{(IPr)C(Ph)}AsCl]2 (4). Remarkably, 4 as well as 2 a can be selectively accessed on treatment of 3 a with an appropriate amount of C2Cl6. Moreover, 3 a readily reacts with PhEEPh (E=Se or Te) at room temperature to give {(IPr)C(Ph)}As(EPh)2 (E=Se 5 a; Te 5 b), revealing the cleavage of As=As and E−E bonds and the formation of As−E bonds. Such highly selective stepwise oxidation (3 a→4→2 a) and bond metathesis (3 a→5 a,b) reactions are unprecedented in main‐group chemistry. [ABSTRACT FROM AUTHOR]

This study deals with the experimental and the theoretical spray tip penetration characteristics of diesel and various biodiesel fuels for charge formation in low temperature combustion engines. A theoretical modified Roisman correlation is validated for far-field spray tip penetration of biodiesel spray based on fuel properties. The biodiesel viscosity is a dominant property affecting the spray characteristics in the model. The modified Roisman correlation is validated with experimental spray tip penetration characteristics for low to high ambient gas densities. The use of unsaturated biodiesel shows a high spray tip penetration even at high ambient gas density. The use of multiple fuel injection technique in low temperature combustion engines with unsaturated biodiesel can be helpful in achieving the optimum charge formation. [ABSTRACT FROM AUTHOR]

Abstract Oxygen rich organic coatings are synthesized in a dielectric barrier discharge at atmospheric pressure. The critical effect of the precursor structure on the final chemical and physical properties of the synthesized coatings and the plasma characteristics are reported. A correlation is proposed between the electrical, optical emission spectroscopy and atmospheric mass spectrometry (MS) measurements of the plasma phase with the chemical properties of the synthesized films. It is shown that the addition of a precursor in an argon plasma leads to a stabilization of the discharge, critically dependent on the precursor structure itself. Different polymerization pathways are evidenced for the saturated and unsaturated precursors by the monitoring of some specific fragments by MS. The polymerized coatings are also characterized with X-Ray Photoelectron Spectroscopy, Infrared Spectroscopy and Atomic Force Microscopy. The presented results not only evidence a stronger preservation of the precursor structure with double bonds in the plasma phase but also reveal the essential role of the distance separating the unsaturation and a function of interest. Highlights • Double bonds in organic precursors modify the electrical behaviour of an atmospheric DBD • Double bonds in organic precursor induce a specific polymerization pathway in the plasma phase • A specific fragment for polymerization is evidenced when double bonds are present • The position of the double bond is of crucial importance in the preservation of the precursor chemistry [ABSTRACT FROM AUTHOR]