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Artigos de revistas sobre o tema "Ether linkage"

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Publicado: 22 de junho de 2024

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1

Andersen, F. Alan. "Special Report: Reproductive and Developmental Toxicity of Ethylene Glycol and Its Ethers". International Journal of Toxicology 18, n.º 2_suppl (março de 1999): 53–67. http://dx.doi.org/10.1177/109158189901800208.

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Polymers of Ethylene Glycol are linked via ether linkages with various alcohols or via ester linkages to various fatty acids in many cosmetic ingredients. Ethylene Glycol, when reacted with an alkyl alcohol, forms an ethylene glycol monoalkyl ether. These compounds are metabolized in the human body by alcohol dehydrogenase and aldehyde dehydrogenase to form corresponding acetaldehyde and acetic acid derivatives. Data are presented that show reproductive and developmental toxicity is associated with metabolites of ethylene glycol monoalkyl ethers, but not with the monoalkyl ethers themselves. Further, it is suggested that the toxicity of these metabolites is inversely proportional to the length of the alkyl chain in the original alkyl ether. In the case of the compounds used in cosmetics, most have alcohols or fatty acids linked to polyethylene glycol chains, not a single Ethylene Glycol moiety. Where Ethylene Glycol is linked to a fatty acid by an ester linkage, the resulting compound is chemically different from the monoalkyl ethers. Where Ethylene Glycol is linked to an alcohol via an ether linkage, the alkyl chain is large and complex, suggesting little or no potential toxicity. Overall, it was found that metabolites of ethylene glycol monoalkyl ethers are reproductive and developmental toxins. In general, however, the metabolites of concern are not expected to be formed in cosmetic formulations that contain polymers of ethylene glycol.

2

Zhou, Jinghui, Xinjin Sui e Haiqiang Shi. "Study on the structural change of lignin during auto-catalyzed ethanol-water pulping of aspen by 1H-NMR". BioResources 4, n.º 3 (1 de junho de 2009): 979–85. http://dx.doi.org/10.15376/biores.4.3.979-985.

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This study concerns the structural change of lignin during auto-catalyzed ethanol-water pulping of aspen by 1H-NMR. The results showed that the linkages of alkyl-aryl ether of lignin, such as the α-ether linkages (α-O-4) and the β-ether linkages (β-O-4), were broken and the alkyl part formed carbenium at the Cα and Cβ of the aliphatic branch. Meanwhile, the aryl part of ether accepted one H+ and formed phenol. Because of the electronegative effect originating from the electron cloud of phenyl, partial carbenium of Cβ was rearranged. Due to its ether or hydroxyl linkage, rearranging to Cβ, the Cα was changed into carbenium and formed a new β-O-4 alkyl-aryl ether. The β-O-4 alkyl-aryl ether was not stable and broken further. So the large molecule of lignin was disintegrated into a smaller one and dissolved into ethanol. Finally, the α+ carbenium reformed α-O-4 linkages of ether with phenol.

3

Duvva, Naresh, A. R. Ramya, Govind Reddy e L. Giribabu. "Intramolecular electron transfer in porphyrin-anthraquinone donor–acceptor systems with varying molecular bridges". Journal of Porphyrins and Phthalocyanines 23, n.º 06 (28 de maio de 2019): 628–38. http://dx.doi.org/10.1142/s1088424619500287.

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Photoinduced electron transfer has been investigated in porphyrin anthraquinone (ZnTTP-AQ) donor–acceptor dyads having either ester (ZnTTP-AQ1) or ether (ZnTTP-AQ2) linkages. Both dyads were characterized by spectroscopic and electrochemical methods. Absorption spectra show absence of any ground state interaction between the porphyrin and anthraquinone moieties. The quenched fluoresence and lifetime indicate electron transfer from the porphyrin to the anthraquinone moiety. The quenching is more pronounced in ZnTTP-AQ1 with ester linkage, suggesting efficient electronic coupling compared to the ether linkage in ZnTTP-AQ2. Computational analysis and frontier molecular orbitals confirmed the formation of charged separated state por[Formula: see text]AQ[Formula: see text]. The electron transfer rates ([Formula: see text] of these triads are found in the range 0.43 × 108 to 10.52 × 109 s[Formula: see text] and are found to be solvent polarity dependent.

4

Bang, Moon-Soo. "Synthesis and Properties of Liquid Crystalline Copolymers with Ether-ether-ester Linkage in Main Chain". Journal of the Korea Academia-Industrial cooperation Society 11, n.º 4 (30 de abril de 2010): 1367–72. http://dx.doi.org/10.5762/kais.2010.11.4.1367.

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5

Zhao, Rui, Pan Shi, Junyou Chen, Shuaishuai Sun, Jingnan Chen, Jibin Cui, Fangming Wu et al. "Chemical synthesis and biological activity of peptides incorporating an ether bridge as a surrogate for a disulfide bond". Chemical Science 11, n.º 30 (2020): 7927–32. http://dx.doi.org/10.1039/d0sc02374d.

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6

Ni, Zhi-Yu, Yi-Bing Wu, Mei Dong, Man-Li Zhang, Yu-Fang Wang, Françoise Sauriol, Chang-Hong Huo et al. "Diabietane Ether, a New Dimeric Abietane with an Ether Linkage from Taxus cuspidata Needles". Zeitschrift für Naturforschung B 66, n.º 10 (1 de outubro de 2011): 1083–86. http://dx.doi.org/10.1515/znb-2011-1015.

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7

Kikuchi, Shuhei, Yugo Iwasaki, Mina Yoshioka, Kodai Hino, Shin-ya Morita, Ryu Tada, Yasuhiro Uchimura et al. "Solitary and Synergistic Effects of Different Hydrophilic and Hydrophobic Phospholipid Moieties on Rat Behaviors". Pharmaceutics 16, n.º 6 (4 de junho de 2024): 762. http://dx.doi.org/10.3390/pharmaceutics16060762.

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Glycerophospholipids have hydrophobic and hydrophilic moieties. Previous studies suggest that phospholipids with different moieties have different effects on rodent behavior; however, the relationship between chemical structures and behavioral effects remains unclear. To clarify the functions of phospholipid moieties, we injected male rats with phospholipids with different moieties and conducted behavioral tests. Exploratory activity was reduced by phosphatidylethanolamine (PE)(18:0/22:6) but not PE(18:0/18:0) or PE(18:0/20:4). Conversely, exploratory activity was increased by plasmanyl PE(16:0/22:6), which harbors an alkyl–ether linkage, but not by phosphatidylcholine (PC)(16:0/22:6) or plasmanyl PC(16:0/22:6). Docosahexaenoic acid (DHA)(22:6) and an alkyl–ether linkage in PE were thus postulated to be involved in exploratory activity. Anxiety-like behavior was reduced by plasmenyl PC(18:0/20:4), which harbors a vinyl–ether linkage, but not by PC(18:0/20:4) or plasmanyl PC(18:0/20:4), suggesting the anxiolytic effects of vinyl–ether linkage. The activation of social interaction was suppressed by PE(18:0/18:0), PE(18:0/22:6), PC(16:0/22:6), plasmanyl PE(16:0/22:6), and plasmanyl PC(16:0/22:6) but not by PE(18:0/20:4), plasmenyl PE(18:0/20:4), or plasmanyl PC(18:0/22:6). DHA may suppress social interaction, whereas arachidonic acid(20:4) or a combination of alkyl–ether linkage and stearic acid(18:0) may restore social deficits. Our findings indicate the characteristic effects of different phospholipid moieties on rat behavior, and may help to elucidate patterns between chemical structures and their effects.

8

Lundquist, Knut, Vratislav Langer e Jim Parkås. "The structure and conformation of lignin as judged by X-ray crystallographic investigations of lignin model compounds: Arylglycerol beta-syringyl ethers". BioResources 4, n.º 2 (5 de março de 2009): 529–36. http://dx.doi.org/10.15376/biores.4.2.529-536.

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Structural elements of the arylglycerol b-syringyl ether type are very frequent in hardwood lignins. A variety of crystalline dimeric lignin models representing different diastereomeric forms of structural elements in lignin of this type have been studied using X-ray crystallography. Bond distances and bond angles in the model compounds are in all probability nearly identical with those of the corresponding structural elements in lignins. Special attention was paid to the geometry of the b-O-syringyl linkage, since the reactivity of this linkage is of particular interest in connection with pulping reactions. The crystal structures of the model compounds suggest that two types of conformations are predominating; in both of them the aromatic rings are separated by ca. 4.5 Å (maximal distance 4.9-5 Å). Based on X-ray crystallographic data from four compounds a sequence of units (5 aromatic rings, 8 chiral C-atoms) attached to each other by b-syringyl ether linkages was constructed. The appearance of the resulting oligomer illustrates that stereoisomerism can be expected to influence the shape of the lignin molecules to a great extent.

9

Xie, Yimin, Xudong Chen, Kai Zhang, Sheng Cui e Gongxia Zhang. "Elucidation of lignin and polysaccharide linkages in wheat straw by 2H/13C isotopic tracer". BioResources 18, n.º 1 (17 de novembro de 2022): 550–69. http://dx.doi.org/10.15376/biores.18.1.550-569.

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To elucidate chemical linkages between lignin and polysaccharides, the aqueous mixed solutions of coniferin-[α-13C], syringin-[α-13C], D-glucose-[6-2H], and phenylalanine ammonia-lyase inhibitor were injected into a living wheat stalk. Internode tissues with high abundance of 2H-13C were collected. The milled wood lignin, lignin-carbohydrate complex (LCC), and residual LCC (R-LCC) with enrichment of 2H-13C were isolated. The 13C and 2H abundances showed that the lignin and polysaccharides of internode tissues were labeled by 13C and 2H, respectively. Analysis with carbon-13 nuclear magnetic resonance (13C-NMR) showed that ketal and benzyl ether bonds were formed between α-C of lignin and carbohydrates. The R-LCC and LCC were further treated with enzymes to obtain enzymatic degraded R-LCC (ED-R-LCC) and enzymatic degraded LCC (ED-LCC). 13C-NMR spectra of ED-LCC showed that the α-C of lignin side chain was combined with 6-C of carbohydrates by ether, ester, and ketal linkages. 1H-NMR differential spectra of ED-LCCs revealed an LC linkage of benzyl ether bond. Glucan-lignin (En-R-GL) and xylan-lignin (En-R-XL) complexes were separated from ED-R-LCC by ionic liquid. A part of lignin α-C was linked to cellulose 6-C by benzyl ether and α-ketal linkages. 13C-NMR spectra of En-R-XL showed there were α-benzyl ether and α-ketal bonds between lignin and xylan.

10

Grainger, James, V. Vikram Reddy e Donald G. Patterson. "Pentachlorodibenzo-p-dioxin Isomer Differentiation by Capillary Gas Chromatography Fourier Transform Infrared Spectroscopy". Applied Spectroscopy 42, n.º 5 (julho de 1988): 800–806. http://dx.doi.org/10.1366/0003702884429166.

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Reference infrared vapor-phase spectra of the 14 pentachlorodibenzo-p-dioxin (PnCDD) isomers were recorded at low microgram concentrations. A unique infrared spectrum corresponding to each chromatographically separated or spectrally subtracted mixture component was observed. The structures for individual isomers in each isomer pair were assigned by qualitative valence-bond evaluations and empirically derived quantitative estimations of ether linkage asymmetric stretching frequencies [ vcoc(asym)] Correlations between calculated ether linkage (C-O-C) bond angles and vcoc(asym) indicate the existence of buttressed 1,6 and 1,9 nonbonded interactions not observed in tetrachlorodibenzo- p-dioxin (TCDD) isomers.

11

Horská, Květa, Aleš Cvekl, Ivan Rosenberg, Antonín Holý e Karel Šebesta. "DNA-dependent RNA polymerase mediated formation of methylphosphonyl internucleotide linkage". Collection of Czechoslovak Chemical Communications 55, n.º 8 (1990): 2100–2109. http://dx.doi.org/10.1135/cccc19902100.

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Analogues of ATP modified in the triphosphate moiety by introducing phosphonylmethyl ether residue(s) were used as substrates for bacterial DNA-dependent RNA polymerase. Although the analogues function as poor substrates they enter the initiation as well as the elongation site of the enzyme. The ATP analogue containing the phosphonylmethyl ether group in the α position in the presence of UTP and poly [d(A-T)] gives rise to alternating di- and trinucleotides with one anomalous internucleotide linkage per molecule.

12

Huang, De-Cheng, Jung-Tsu Wu, Yang-Ze Fan e Guey-Sheng Liou. "Preparation and optoelectronic behaviours of novel electrochromic devices based on triphenylamine-containing ambipolar materials". Journal of Materials Chemistry C 5, n.º 36 (2017): 9370–75. http://dx.doi.org/10.1039/c7tc02953e.

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13

Das, Avijit Kumar, Shyamaprosad Goswami, Ching Kheng Quah e Hoong-Kun Fun. "Neighbouring group participation of thiol through aldehyde group assisted thiolysis of active ether: ratiometric and vapor phase fast detection of hydrogen sulfide in mixed aqueous media". New Journal of Chemistry 39, n.º 7 (2015): 5669–75. http://dx.doi.org/10.1039/c5nj00689a.

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14

Yin, Chongxin, Min Wang, Qingzhi Ma, Huiyang Bian, Hao Ren, Hongqi Dai e Jinlan Cheng. "Valorization of Rice Straw via Hydrotropic Lignin Extraction and Its Characterization". Molecules 26, n.º 14 (6 de julho de 2021): 4123. http://dx.doi.org/10.3390/molecules26144123.

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Rice straw hydrotropic lignin was extracted from p-Toluene sulfonic acid (p-TsOH) fractionation with a different combined delignification factor (CDF). Hydrotropic lignin characterization was systematically investigated, and alkaline lignin was also studied for the contrast. Results showed that the hydrotropic rice straw lignin particle was in nanometer scopes. Compared with alkaline lignin, the hydrotropic lignin had greater molecular weight. NMR analysis showed that β-aryl ether linkage was well preserved at low severities, and the unsaturation in the side chain of hydrotropic lignin was high. H units and G units were preferentially degraded and subsequently condensed at high severity. High severity also resulted in the cleavage of part β-aryl ether linkage. 31P-NMR showed the decrease in aliphatic hydroxyl groups and the increasing carboxyl group content at high severity. The maximum weight loss temperature of the hydrotropic lignin was in the range of 330–350 °C, higher than the alkaline lignin, and the glass conversion temperature (Tg) of the hydrotropic lignin was in the range of 107–125 °C, lower than that of the alkaline lignin. The hydrotropic lignin has high β-aryl ether linkage content, high activity, nanoscale particle size, and low Tg, which is beneficial for its further valorization.

15

Ni, Z. Y., Y. B. Wu, M. Dong, M. L. Zhang, Y. F. Wang, F. Sauriol, C. H. Huo et al. "Diabietane Ether, a New Dimeric Abietane with an Ether Linkage from Taxus cuspidata Needles". Zeitschrift für Naturforschung B 66 (2011): 1083. http://dx.doi.org/10.5560/znb.2011.66b1083.

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16

García-Sosa, Karlina, Rodolfo Aldana-Pérez, Reyna V. Ek Moo, Paulino Simá-Polanco e Luis M. Peña-Rodríguez. "Dinimbidiol Ether, a Novel Bioactive Dimeric Diterpene from the Root Extract of Cnidoscolus souzae". Natural Product Communications 12, n.º 9 (setembro de 2017): 1934578X1701200. http://dx.doi.org/10.1177/1934578x1701200903.

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The radical scavenging assay-guided fractionation of the root extract of Cnidoscolus souzae resulted in the isolation and identification of a novel bioactive dimeric diterpene with an ether linkage which has been designated as dinimbidiol ether (2). Evaluation of the antioxidant activity using the DPPH reduction assay showed that 2 is the most active metabolite in the crude extract of the plant.

17

R., Balasubramanian, Fathima Rigana M., Balaji S., Selvamani A. e Sarojadevi M. "New polytriazoleimides containing green synthesized titanium dioxide using Artemisia pallens plant extract: optical, dielectric, thermal and mechanical properties". New Journal of Chemistry 41, n.º 7 (2017): 2815–25. http://dx.doi.org/10.1039/c6nj03164a.

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18

Kuang, Tongdong, Hui-Qin Chen, Hao Wang, Fan-Dong Kong, Cai-Hong Cai, Wen-Hua Dong, Jing-Zhe Yuan, Wen-Li Mei e Hao-Fu Dai. "UPLC-MS-guided isolation of single ether linkage dimeric 2-(2-phenylethyl)chromones from Aquilaria sinensis". RSC Advances 9, n.º 30 (2019): 17025–34. http://dx.doi.org/10.1039/c9ra02597a.

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Eleven novel uncommon single ether linkage dimeric 2-(2-phenylethyl)chromones (aquilasinenones A–K) were isolated by a UPLC-MS guided method from artificial hole-induced agarwood originating from Aquilaria sinensis.

19

De Gregorio, Gilbert F., Cameron C. Weber, John Gräsvik, Tom Welton, Agnieszka Brandt e Jason P. Hallett. "Mechanistic insights into lignin depolymerisation in acidic ionic liquids". Green Chemistry 18, n.º 20 (2016): 5456–65. http://dx.doi.org/10.1039/c6gc01295g.

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20

Li, Xiaochen, Masahiko Miyauchi, Carlos González e Steven Nutt. "Thermal oxidation of PEPA-terminated polyimide". High Performance Polymers 31, n.º 6 (19 de julho de 2018): 707–18. http://dx.doi.org/10.1177/0954008318787852.

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The thermal oxidative stability of a 4-phenylethynyl phthalic anhydride (PEPA) endcapped polyimide (PI) was investigated. A surface reaction layer formed due to oxidization during thermal aging and grew in thickness with increasing aging time. Analysis of the surface layer revealed a partial loss of aromatic ring, ether linkage, and imide linkage in the aged polymer. The partial loss of the imide linkage and ether linkage in the surface layer was corroborated by the observed release of carbon monoxide and carbon dioxide reaction products. The oxidized layer exhibited discoloration and an increase in glass transition temperature. The surface discoloration was attributed to the formation of the conjugated unsaturated or aromatic carbonyl groups and/or the charge transfer complex. Interior regions of the oxidized samples were largely unaffected, except for a more compact molecular configuration. Compared with aging at high temperatures (288°C, 316°C), aging at 204°C produced similar chemical changes in the cured polymer, albeit with a low degradation rate. The oxidative stability of the imide polymer surpassed that of conventional nadic-endcapped PIs due to the greater intrinsic thermal stability of the PEPA endcap. The unusual oxidative stability of the PI, combined with superior mechanical properties, warrant consideration as a composite matrix for future applications in high-temperature service conditions.

21

Gao, Chunmei, Jiale Chen, Boping Zhang e Lei Wang. "Effect of Chemical Structure and Degree of Branching on the Stability of Proton Exchange Membranes Based on Sulfonated Polynaphthylimides". Polymers 12, n.º 3 (12 de março de 2020): 652. http://dx.doi.org/10.3390/polym12030652.

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Hydrolytic stability and oxidative stability are the core properties of sulfonated polynaphthylimides (SPIs) as proton exchange membranes. The chemical structure of SPIs directly influences the performance. Herein, three different series of branched SPIs were designed and prepared using 1,3,5-tris (2-trifluoromethyl-4-aminophenoxy) benzene as a trifunctional monomer and three non-sulfonated diamine monomers, such as 4,4′-oxydianiline (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (6FODA), and 4,4′-(9-fluorenylidene)dianiline (BFDA). The effect of the chemical structure and degree of branching on SPIs properties is discussed. The results showed that by controlling the chemical structure and degree of branching, the chemical stability of SPIs changed significantly. SPI-6FODA with two ether linkages and a hydrophobic CF3 group has higher hydrolytic stability than SPI-ODA with only one ether linkage. In addition, with the increase of the introduced B3 monomer, the oxidation stability of SPI-6FODA has been greatly improved. We successfully synthesized SPIs with a high hydrolytic stability and oxidative stability.

22

Grainger, James, e Leslie T. Gelbaum. "Tetrachlorodibenzo-p-Dioxin Isomer Differentiation by Capillary Gas Chromatography Fourier Transform-Infrared Spectroscopy". Applied Spectroscopy 41, n.º 5 (julho de 1987): 809–20. http://dx.doi.org/10.1366/0003702874448391.

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Reference infrared vapor-phase spectra of the 22 tetrachlorodibenzo-dioxin (TCDD) isomers were recorded at low microgram concentrations. These reference spectra of synthetic mixture components separated chromatographically or by spectral subtraction exhibit distinct infrared spectra for each isomer. The infrared frequencies are delineated in correlation tables and are interpreted in terms of substitution patterns which determine the strength of the ether linkage. Absorbance values in the 1330–1280 cm−1 (C-O-C asymmetric stretch) region correlate with specific substitution patterns and molecular geometry. Relative electron-withdrawing capacities for chlorinated aromatic rings in TCDD isomers were estimated on the basis of relative capacities determined for model compounds. Qualitative correlations were established between electron-withdrawing capacities and the effects of resonance and field interactions on the ether linkage absorption frequencies of individual TCDD isomers. Gas chromatography Fourier transform infrared (GC/FT-IR) isomer assignments are generally consistent with those obtained by proton Fourier transform nuclear magnetic resonance (1H FT/NMR) and flame ionization gas chromatography (GC/FID). A chromatographically independent method of assigning TCDD isomer structures on the basis of ether linkage asymmetric stretching frequencies was established by utilization of valence-bond approximations. GC/FT-IR assignments for several TCDD isomers differ from isomer assignments in previously published results. A user-generated, vapor-phase reference library, containing individual TCDD spectra and spectra of isomer pairs that are incompletely resolved on chromatographic columns, correctly identified each isomer in variety of mixtures by means of a software algorithm.

23

Jin, Chen, Qiumeng Zhang e Wei Lu. "Selective turn-on near-infrared fluorescence probe for hypoxic tumor cell imaging". RSC Advances 7, n.º 30 (2017): 18217–23. http://dx.doi.org/10.1039/c7ra01466j.

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In this study, we designed a new selective turn on near-infrared fluorescence probe by conjugating (1-methyl-2-nitro-1H-imidazol-5-yl)methanol to DCPO with ether linkage for hypoxic tumor cell imaging.

24

Samanta, Partha, Aamod V. Desai, Bihag Anothumakkool, Mandar M. Shirolkar, Avishek Karmakar, Sreekumar Kurungot e Sujit K. Ghosh. "Enhanced proton conduction by post-synthetic covalent modification in a porous covalent framework". Journal of Materials Chemistry A 5, n.º 26 (2017): 13659–64. http://dx.doi.org/10.1039/c7ta00964j.

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Ether linkage based chemically stable porous covalent framework has been synthesized which upon post-synthetic modification presents a remarkably high proton conductivity (∼0.026 S cm⁻¹) with an ∼130 fold enhancement compared to parent compound.

25

Patel, Ritesh, Jignesh Patel, Manish Patel e Rawan Patel. "Synthesis and characterization of ether linkage containing bis-fluoran compounds". Journal of the Serbian Chemical Society 68, n.º 8-9 (2003): 607–13. http://dx.doi.org/10.2298/jsc0309607p.

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2?-chloro-6?-diethylaminofluoran and 2?-chloro-3?-methyl-6?-diethylaminofluoran were reacted with various diphenols in dimethyl formamide in the presence of potassium carbonate to give the related bisfluoran compounds. All the synthesized derivatives were identified by conventional methods (IR, 1H-NMR), elemental analysis and UV-visible spectroscopy in organic solvent and 95 % acetic acid. All the fluoran compounds change their color in acidic media.

26

Takahashi, Hideyo, Toshimitsu Fukuda, Haruhiko Mitsuzuka, Rie Namme, Hidetoshi Miyamoto, Yasufumi Ohkura e Shiro Ikegami. "Development of a Novel Sugar Linkage: 6,6′-Ether-Connected Sugars". Angewandte Chemie International Edition 42, n.º 41 (27 de outubro de 2003): 5069–71. http://dx.doi.org/10.1002/anie.200352388.

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27

Takahashi, Hideyo, Toshimitsu Fukuda, Haruhiko Mitsuzuka, Rie Namme, Hidetoshi Miyamoto, Yasufumi Ohkura e Shiro Ikegami. "Development of a Novel Sugar Linkage: 6,6′-Ether-Connected Sugars". Angewandte Chemie 115, n.º 41 (27 de outubro de 2003): 5223–25. http://dx.doi.org/10.1002/ange.200352388.

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28

Craik, DJ, PR Andrews, C. Border e SLA Munro. "Conformational Studies of Thyroid Hormones. I. The Diphenyl Ether Moiety". Australian Journal of Chemistry 43, n.º 5 (1990): 923. http://dx.doi.org/10.1071/ch9900923.

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Conformational flexibility round the diphenyl ether linkage in the thyroid hormones has been investigated by means of molecular orbital (AM1) and classical potential-energy calculations. The results obtained from these theoretical approaches are in qualitative agreement with those from n.m.r. spectroscopy, i.e., the barrier to rotation around this structural feature is sufficiently low to allow rapid interconversion between two stable conformers to occur at room temperature. Two pathways of rotation around the diphenyl ether bridge were explored and were both calculated to be approximately 14-15 kJ mol-1 by the AM1 method. This compares with the experimental barrier of 36 kJ mol-1. The potential-energy calculations gave barriers up to an order of magnitude larger which were inconsistent with experimental observations. A comparison of the AM1 data with results from previous studies with CNDO/2, which predicted a larger barrier, is also given. The detailed mode of interconversion around the two torsion angles involved in diphenyl ether rotation is investigated, as is the interplay of the bulky iodo substituents with the second aromatic ring during such conformational changes. The nature of torsion angle cooperation during rotations around this linkage is discussed.

29

Kishimoto, T., e Y. Sano. "Delignification Mechanism during High-Boiling Solvent Pulping. Part 1. Reaction of Guaiacylglycerol-β-Guaiacyl Ether". Holzforschung 55, n.º 6 (6 de novembro de 2001): 611–16. http://dx.doi.org/10.1515/hf.2001.100.

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Summary A phenolic β-O-4 type lignin model compound, guaiacylglycerol-β-guaiacyl ether (1) was treated with 70 wt% aq 1,3-butanediol solution at 160–200°C to investigate the delignification mechanism under HBS (high-boiling solvent) pulping conditions. The following compounds were identified from the reaction products by use of GC-MS: guaiacol (2), coniferyl alcohol (3), γ-etherified coniferyl alcohols (4) and α-etherified guaiacylglycerol-β-guaiacyl ethers (5), but acidolysis products, such as Hibbert's ketones were not detected. These results strongly suggest that the phenolic β-O-4 linkage was cleaved homolytically under HBS pulping conditions. The cleavage of β-ether exhibited a pseudo first-order rate behavior. The pseudo first-order rate constants were as follows: k = 0.94 × 10−2 min−1 at 160 °C; k = 1.97 × 10−2 min−1 at 170°C; k = 3.22 × 10−2 min−1 at 180 °C; k = 9.76 x 10−2 min−1 at 200 °C. The activation energy was 98.3 kJmol−1. The formation of higher molecular weight compounds was confirmed by GPC. It is highly probable that the oligomeric products were derived from the recombination of phenoxy radicals formed by homolysis of the β-aryl ether.

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Ganesh, Shimoga D., Vasantakumar K. Pai, Mahadevappa Y. Kariduraganavar e Madhu B. Jayanna. "Thermal and Dielectric Behavior Studies of Poly(Arylene Ether Sulfone)s with Sulfonated and Phosphonated Pendants". Journal of Materials 2016 (24 de agosto de 2016): 1–10. http://dx.doi.org/10.1155/2016/7271959.

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The present paper discusses the aspects of the synthesizing valeric acid based poly(ether sulfone)s with active carboxylic acid pendants (VALPSU) from solution polymerization technique via nucleophilic displacement polycondensation reaction among 4,4′-dichlorodiphenyl sulfone (DCDPS) and 4,4′-bis(4-hydroxyphenyl) valeric acid (BHPA). The conditions necessary to synthesize and purify the polymer were investigated in some detail. The synthesized poly(ether sulfone)s comprise sulfone and ether linkages in addition to reactive carboxylic acid functionality; these active carboxylic acid functional groups were exploited to hold the phenyl sulphonic acid and phenyl phosphonic acid pendants. The phenyl sulphonic acid pendants in VALPSU were easily constructed by altering active carboxylic acid moieties by sulfanilic acid using N,N′-dicyclohexylcarbodiimide (DCC) mediated mild synthetic route, whereas the latter one was built in two steps. Initially, polyphosphoric acid condensation with VALPSU by 4-bromoaniline and next straightforward palladium catalyzed synthetic route, in both of which acidic pendants are clenched by polymer backbone via amide linkage. Without impairing the primary polymeric backbone modified polymers were prepared by varying the stoichiometric ratios of respective combinations. All the polymers were physicochemically characterized and pressed into tablets; electrical contacts were established to study the dielectric properties. Finally, the influence of the acidic pendants on the dielectric properties was examined.

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Shi, Qing-Wen, e et al et al. "ChemInform Abstract: Diabietane Ether, a New Dimeric Abietane with an Ether Linkage from Taxus cuspidata Needles." ChemInform 43, n.º 10 (9 de fevereiro de 2012): no. http://dx.doi.org/10.1002/chin.201210204.

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Qi, Yinghua, Akash Nathani, Jianxin Zhang, Zhengji Song, Chandra Shekhar Sharma e Sunil K. Varshney. "Synthesis of amphiphilic poly(ethylene glycol)-block-poly(methyl methacrylate) containing trityl ether acid cleavable junction group and its self-assembly into ordered nanoporous thin films". e-Polymers 20, n.º 1 (10 de março de 2020): 111–21. http://dx.doi.org/10.1515/epoly-2020-0013.

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AbstractA strategy for the synthesis of well defined poly(ethylene glycol)-block-poly(methyl methacrylate) diblock copolymers containing trityl ether acid cleavable junctions is demonstrated. This approach is achieved by using a combination of poly(ethylene glycol) macroinitiator containing a trityl ether end group, which is susceptible to acid cleavage, and atom transfer radical polymerization technique. The trityl ether linkage between blocks can be readily cleaved in solution or in solid phase under very mild acid condition, which has been confirmed by 1H NMR. These diblock copolymers have been used to successfully fabricate nanoporous thin films by acid cleavage of trityl ether junction followed by complete removal of poly(ethylene glycol) block. The fabricated nanoporous thin films may have a wide range of application such as Recessed Nanodisk-array electrode (RNE) or as a template to fabricate nanoelectrode array for senor applications.

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Ando, Daisuke, Toshiyuki Takano e Fumiaki Nakatsubo. "Multi-step degradation method for β-O-4 linkages in lignins: α-TSA method. Part 1: Reaction of non-phenolic dimeric β-O-4 model compound". Holzforschung 68, n.º 4 (1 de maio de 2014): 369–75. http://dx.doi.org/10.1515/hf-2013-0126.

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Abstract The α-TSA method has been developed for the cleavage of β-O-4 linkages in lignin. It consists of three steps: (1) thioetherification at α-position of β-O-4 substructures, (2) sulfonylation, and (3) mild alkali treatment of the α-sulfone derivative. The method was tested on a nonphenolic dimeric β-O-4 lignin model compound, namely on 4-benzyloxy-3-methoxyphenylglycerol-β-guaiacyl ether. It demonstrated that the mild alkali degradation of the α-sulfone derivative proceeds efficiently, i.e., the electron-withdrawing sulfone group at α-position contributes to the cleavage of the β-O-4 linkage in the same mechanism as that in the γ-TTSA method.

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Beltz, Mark W., e Frank W. Harris. "Synthesis and properties of aromatic polyimides containing oxyalkylene linkages". High Performance Polymers 7, n.º 1 (fevereiro de 1995): 23–40. http://dx.doi.org/10.1088/0954-0083/7/1/003.

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A series of para-catenated aromatic diamines containing oxyalkylene linkages, i.e., i.2-bis(4-aminophenoxy)ethane, bis[2-(4-aminnophenoxy)ethyl]ether, 1,2-bis[24{4-aminio-phenoxy)ethoxyjethane and bis{2-[2A4-aminophenoxy)ethoxy]ethyllether were polymerized with 3,3',4.4'benzophenonetetracarboxylic dianhydride (BTDA) and pyromellitic dianhydride. The poly(amic acid)s obtained were imidized by both chemical and thermal methods. It was postulated that the incorporation of the flexible linkages in the polyimides' backbones would result in solubility in organic solvents and moderate glass transition temperatures (Tg) that would allow the polymers to be melt processed. However, the polyimides were insoluble and highly crystalline with melting points (Tm) above 400"C. In an attempt to disrupt the polymers' symmetry. mixtures of the diamines and 1,3-bis(3-aminophenoxy)benzene were polymerized with BTDA. The resulting copolymers were insoluble and semrnicrystalline with Tm values near 310C. A polyimide with similar properties was obtained by polymerizing a disubstituted diamine, 2,2-diethyl-t,3-bis(4-aminophenoxy)propane, with BTDA. A soluble polymer that could be melt processed was prepared from BTDA and a meta-catenated diamine containing an oxyalkylene linkage, bis[2-(3-aminophenoxy)ethyl)ether. The polymer had a strong Tg near 156 'C and a weak Tm near 240C.

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Fontaine, Delphine, Sandy Figiel, Romain Félix, Sana Kouba, Gaëlle Fromont, Karine Mahéo, Marie Potier-Cartereau, Aurélie Chantôme e Christophe Vandier. "Roles of endogenous ether lipids and associated PUFAs in the regulation of ion channels and their relevance for disease". Journal of Lipid Research 61, n.º 6 (7 de abril de 2020): 840–58. http://dx.doi.org/10.1194/jlr.ra120000634.

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Ether lipids (ELs) are lipids characterized by the presence of either an ether linkage (alkyl lipids) or a vinyl ether linkage [i.e., plasmalogens (Pls)] at the sn1 position of the glycerol backbone, and they are enriched in PUFAs at the sn2 position. In this review, we highlight that ELs have various biological functions, act as a reservoir for second messengers (such as PUFAs) and have roles in many diseases. Some of the biological effects of ELs may be associated with their ability to regulate ion channels that control excitation-contraction/secretion/mobility coupling and therefore cell physiology. These channels are embedded in lipid membranes, and lipids can regulate their activities directly or indirectly as second messengers or by incorporating into membranes. Interestingly, ELs and EL-derived PUFAs have been reported to play a key role in several pathologies, including neurological disorders, cardiovascular diseases, and cancers. Investigations leading to a better understanding of their mechanisms of action in pathologies have opened a new field in cancer research. In summary, newly identified lipid regulators of ion channels, such as ELs and PUFAs, may represent valuable targets to improve disease diagnosis and advance the development of new therapeutic strategies for managing a range of diseases and conditions.

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Chen, Changzhou, Peng Liu, Haihong Xia, Minghao Zhou, Jiaping Zhao, Brajendra K. Sharma e Jianchun Jiang. "Photocatalytic Cleavage of β-O-4 Ether Bonds in Lignin over Ni/TiO2". Molecules 25, n.º 9 (30 de abril de 2020): 2109. http://dx.doi.org/10.3390/molecules25092109.

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It is of great importance to explore the selective hydrogenolysis of β-O-4 linkages, which account for 45–60% of all linkages in native lignin, to produce valued-added chemicals and fuels from biomass employing UV light as catalyst. TiO2 exhibited satisfactory catalytic performances in various photochemical reactions, due to its versatile advantages involving high catalytic activity, low cost and non-toxicity. In this work, 20 wt.% Ni/TiO2 and oxidant PCC (Pyridinium chlorochromate) were employed to promote the cleavage of β-O-4 alcohol to obtain high value chemicals under UV irradiation at room temperature. The Ni/TiO2 photocatalyst can be magnetically recovered and efficiently reused in the following four consecutive recycling tests in the cleavage of β-O-4 ether bond in lignin. Mechanism studies suggested that the oxidation of β-O-4 alcohol to β-O-4 ketone by oxidant PCC first occurred during the reaction, and was followed by the photocatalysis of the obtained β-O-4 ketone to corresponding acetophenone and phenol derivates. Furthermore, the system was tested on a variety of lignin model substrates containing β-O-4 linkage for the generation of fragmentation products in good to excellent results.

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Obenhuber, A. H., T. L. Gianetti, R. G. Bergman e J. Arnold. "Regioselective [2+2] and [4+2] cycloaddition reactivity in an asymmetric niobium(bisimido) moiety towards unsaturated organic molecules". Chemical Communications 51, n.º 7 (2015): 1278–81. http://dx.doi.org/10.1039/c4cc07851a.

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The asymmetric bis-imido structure and the lability of the diethyl ether linkage in complex 1 provide a niobium complex that undergoes regioselective [4+2] cycloaddition reactions with an α,β-unsaturated ketone and cycloaddition reactions that involve bond formation to the MAD ligand (MAD = monoazabutadiene).

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Hashimoto, Makoto, Yuka Tsunekawa, Katsuyoshi Masuda, Miho Muto, Yasuyuki Muto, Yuta Murai, Yasuyuki Hashidoko, Yoshitake Orikasa, Yuji Oda e Yasumaru Hatanaka. "Chemo-Enzymatic Synthesis of 1’-Photoreactive Sucrose Derivatives via Ether Linkage". HETEROCYCLES 84, n.º 1 (2012): 283. http://dx.doi.org/10.3987/com-11-s(p)19.

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Scalbert, A. "Ether linkage between phenolic acids and lignin fractions from wheat straw". Phytochemistry 24, n.º 6 (1985): 1359–62. http://dx.doi.org/10.1016/s0031-9422(00)81133-4.

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Parry, Ronald J., Rajesh Turakhia e Buu Hanh Phuoc. "The biosynthesis of furanomycin. Mechanism of formation of the ether linkage". Journal of the American Chemical Society 110, n.º 12 (junho de 1988): 4035–36. http://dx.doi.org/10.1021/ja00220a051.

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Brandis, Alexander S., Andre N. Kozyrev e Andrey F. Mironov. "Synthesis and study of chlorin and porphyrin dimers with ether linkage". Tetrahedron 48, n.º 31 (janeiro de 1992): 6485–94. http://dx.doi.org/10.1016/s0040-4020(01)88238-7.

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Ainsworth, Peter J., Donald Craig, John C. Reader, Alexandra M. Z. Slawin, Andrew J. P. White e David J. Williams. "Intramolecular Diels-Alder reactions of trienes tethered with an ether linkage". Tetrahedron 52, n.º 2 (janeiro de 1996): 695–724. http://dx.doi.org/10.1016/0040-4020(95)00920-5.

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Kaya, İsmet, e Musa Kamacı. "Synthesis, optical, and thermal properties of polyimides containing flexible ether linkage". Journal of Applied Polymer Science 135, n.º 31 (23 de abril de 2018): 46573. http://dx.doi.org/10.1002/app.46573.

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Afsar, Ashfaq, Laurence M. Harwood, Michael J. Hudson, Mark E. Hodson e Elizabeth J. Shaw. "Neocuproine-functionalized silica-coated magnetic nanoparticles for extraction of copper(ii) from aqueous solution". Chem. Commun. 50, n.º 56 (2014): 7477–80. http://dx.doi.org/10.1039/c4cc01250j.

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Neocuproine has been covalently bound to silica-coated maghemite (γ-Fe₂O₃) magnetic nanoparticles (MNPs) by a phenyl ether linkage. The resulting MNPs are able to remove Cu(ii) from 12 ppm aqueous solution with an extraction efficiency of up to 99% at pH 2.

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Ganesh, S. D., M. N. K. Harish, B. J. Madhu, Husnasarvari Maqbool, K. V. Pai e M. Y. Kariduraganavar. "Poly(Arylene Ether Sulfone)s with HEPES Pendants: Synthesis, Thermal, and Dielectric Studies". ISRN Polymer Science 2013 (29 de maio de 2013): 1–7. http://dx.doi.org/10.1155/2013/897034.

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Polyethersulfone with active carboxylic acid pendants was prepared from solution polymerization via nucleophilic displacement polycondensation reaction among 4,4′-dichlorodiphenyl sulfone (DCDPS) and 4,4′-bis(4-hydroxyphenyl) valeric acid (BHPA). The conditions necessary to synthesize and purify the polymer were investigated in some details. The synthesized polyethersulfone comprises sulfone and ether linkages in addition to reactive carboxylic acid functionality; this reactive carboxylic acid group was exploited to hold the HEPES moiety via ester linkage and is achieved by simple DCC coupling condition at ambient temperature. Without impairing the primary polymeric backbone, three modified polymers were prepared by varying the stoichiometric ratio of HEPES. Characterization of the polymers by 1H & 13C NMR, FT-IR, and TGA demonstrated that HEPES was quantitatively incorporated into the prime polymer. All the prepared polymers were pressed into tablets, and electrical contacts were established to study the dielectric properties. Finally, the influence of the HEPES on the dielectric properties was examined.

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Gomes, Marco Antônio G. B., Alicia Bauduin, Chloé Le Roux, Romain Fouinneteau, Wilfried Berthe, Mathieu Berchel, Hélène Couthon e Paul-Alain Jaffrès. "Synthesis of ether lipids: natural compounds and analogues". Beilstein Journal of Organic Chemistry 19 (8 de setembro de 2023): 1299–369. http://dx.doi.org/10.3762/bjoc.19.96.

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Ether lipids are compounds present in many living organisms including humans that feature an ether bond linkage at the sn-1 position of the glycerol. This class of lipids features singular structural roles and biological functions. Alkyl ether lipids and alkenyl ether lipids (also identified as plasmalogens) correspond to the two sub-classes of naturally occurring ether lipids. In 1979 the discovery of the structure of the platelet-activating factor (PAF) that belongs to the alkyl ether class of lipids increased the interest in these bioactive lipids and further promoted the synthesis of non-natural ether lipids that was initiated in the late 60’s with the development of edelfosine (an anticancer drug). More recently, ohmline, a glyco glycero ether lipid that modulates selectively SK3 ion channels and reduces in vivo the occurrence of bone metastases, and other glyco glycero ether also identified as GAEL (glycosylated antitumor ether lipids) that exhibit promising anticancer properties renew the interest in this class of compounds. Indeed, ether lipid represent a new and promising class of compounds featuring the capacity to modulate selectively the activity of some membrane proteins or, for other compounds, feature antiproliferative properties via an original mechanism of action. The increasing interest in studying ether lipids for fundamental and applied researches invited to review the methodologies developed to prepare ether lipids. In this review we focus on the synthetic method used for the preparation of alkyl ether lipids either naturally occurring ether lipids (e.g., PAF) or synthetic derivatives that were developed to study their biological properties. The synthesis of neutral or charged ether lipids are reported with the aim to assemble in this review the most frequently used methodologies to prepare this specific class of compounds.

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Shabaev, Albert S., Azamat A. Zhansitov e S. Yu Khashirova. "Thermal Stability of Polyetherketones". Materials Science Forum 935 (outubro de 2018): 31–35. http://dx.doi.org/10.4028/www.scientific.net/msf.935.31.

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The thermal stability of polyether ketone, polyetheretherketone, polyarylene ketone at 400-500 °C was studied by gas chromatography. It was found out that the thermal destruction of polyetherketones and polyetheretherketones begins with the rupture of the ketone group, and polyarylene ketones with the detachment of the methyl group and the rupture of the ether linkage of the diane fragment.

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Muslim, Mohd, Arif Ali, Saima Kamaal, Musheer Ahmad, Mohd Afzal e Maksym O. Plutenko. "Crystal structure and Hirshfeld surface analysis of diethyl 5-(2-cyanophenoxy)isophthalate". Acta Crystallographica Section E Crystallographic Communications 76, n.º 6 (22 de maio de 2020): 905–8. http://dx.doi.org/10.1107/s2056989020004508.

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The title compound, C19H17NO5, obtained by ether bond formation between the reagents, crystallizes in the monoclinic space group P21/c. The compound is non-planar, subtending a dihedral angle of 82.38 (4)° between the plane of hydroxy isophthalate-based ester and that of the benzonitrile moiety. The molecule is bent at the ether linkage, with a Caryl—O—Caryl bond angle of 116.74 (11)°. In the crystal, molecules are linked by C—H...O hydrogen bonds and other weak interactions forming a supramolecular framework. A Hirshfeld surface analysis was performed to generate two-dimensional fingerprint plots, which reveal the type of interactions occurring in the vicinity of the molecule.

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Lu, Yunhua, Jican Hao, Guoyong Xiao, Lin Li, Zhizhi Hu e Tonghua Wang. "Optical, thermal and gas separation properties of acetate-containing copoly(ether-imide)s based on 6FDA and fluorenyl diamines". High Performance Polymers 31, n.º 9-10 (9 de janeiro de 2019): 1101–11. http://dx.doi.org/10.1177/0954008318822118.

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The diamine, 9,9-bis[4-(4-amino-3-hydroxylphenoxy)phenyl]fluorene (BAHPPF) was synthesized by the modified two-step method. Then, a series of acetate-containing copoly(ether-imide)s were prepared by the copolymerization of BAHPPF, 9,9-bis(4-aminophenyl)fluorene (BAF) and 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) followed by chemical imidization. The structures and properties of the BAHPPF and copoly(ether-imide)s were characterized by nuclear magnetic resonance spectrometer (NMR), Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), ultraviolet-visible spectrophotometer (UV-VIS), and tensile testing. Single gas permeation performances of these copoly(ether-imide)s were also studied for five representative gases of interest including H2, O2, N2, CO2, and CH4. The experimental results showed that the copoly(ether-imide)s showed excellent optical properties with high light transmittance above 80.2% at 450 nm. The glass transition temperature of these copolymers were higher than 333°C. Their tensile strength and Young’s module also increased, and the elongation decreased with the decrease of BAHPPF. High gas permeabilities of copoly(ether-imide)s were obtained, and the ideal selectivity of CO2/CH4 was improved due to the introduction of acetate group and flexible ether linkage. These copoly(ether-imide)s could be applied to the field of optics and gas separation.

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Guo, Hao, Mingyue Wang, Rui Xue, Jing Yao, Xuejiao Wang, Longwen Zhang, Jianfeng Liu e Wu Yang. "A new COF linked by an ether linkage (–O–): synthesis, characterization and application in supercapacitance". RSC Advances 9, n.º 24 (2019): 13458–64. http://dx.doi.org/10.1039/c9ra01357a.

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A new COF (NWNU-COF-4) linked by aryl ether bonds was readily synthesized by condensation of 2,4,6-trihydroxypyrimidine and trinitrophenol. It exhibited excellent pseudocapacitive performance and cycling stability, with promising application as a supercapacitor electrode.