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1.
While transition metals are well known for assuming the formal oxidation state of zero in various compounds main group elements have rarely engaged in this practice. Recent reports of N-heterocyclic carbene-stabilized main group diatomic allotropes (i.e., Si(2), Ge(2), P(2), As(2)) denote a breakthrough of zero-oxidation state main group chemistry. This Perspective addresses the synthesis and characterization of these highly reactive main group molecules, with a particular emphasis on the very recent progress in the reactivity study of carbene-stabilized Si(2) and P(2). 相似文献
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简单介绍了生物柴油的生产原料,综述了用废弃油脂生产生物柴油的现状和方法。废弃油脂生产生物柴油的方法主要有物理法和化学法,物理法主要有掺和法和微乳法,化学法主要有热裂解法和酯交换法。目前生产中采用化学法的酯交换法、以酸碱两步催化法的工艺为主,而生物酶法和超临界法是研究热点。 相似文献
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岛津GC-16A型气相色谱仪因CRT显示器控制电路故障而导致主机死机,进而造成CR-7A型数据处理机无法与主机联机而死机。通过分析故障现象和电路结构,对主机部分电路进行改造,完全拆除主机上的CRT显示器控制电路,直接通过CR-7A型数据处理机控制主机,使主机不受CRT显示器控制电路的影响而稳定地工作。经改造后,气相色谱仪工作正常,不再出现死机现象。 相似文献
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VT CPMAS NMR measurements were carried out for a series of poly(alkyl l-glutamate)s (PALG) which have n-alkyl side chains with carbon numbers ranging from 2 to 12 in order to investigate the structure and mobility of the main and the side chains. From the temperature dependencies of the peak intensities for the PALGs, the relative mobilities of the main and side chains are discussed. For PG-2 and PG-4, the molecular motions of both the main and side chains are not very fast. From the amount ratio between the main and side chains, the main chain dominates the entire mobility of the polymer. As the side chain length increases, the side chain motion is drastically activated by a temperature change. In addition, the main chain motion is induced by the side chain motion. For PALGs with long alkyl side chains, the mobilities of the polymers are governed by the structure and mobility of the side chain. 相似文献
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Steroid profiles of hemofiltrates of uremic patients contain as main steroids the sulfates of 11beta-hydroxyetiocholanolone, 11-ketoetiocholanolone, 11beta-hydroxyandrosterone and 11-ketoandrosterone. In blood of uremic patients androstenediol is the main steroid of the sulfate fraction, while in blood of healthy persons dehydroepiandrosterone sulfate is the main steroid. The gradual decrease of the kidney function is characterized by an increase of 11-oxigenated androstane conjugates in urine. 相似文献
7.
R. F. Khamidullin N. Yu. Bashkirtseva A. I. Abdullin I. I. Akhmetov 《Russian Journal of Applied Chemistry》2006,79(11):1853-1856
The main physicochemical properties of polyethylene glycol monomethyl ethers in a wide temperature range were determined. The effect exerted on the main quality indices of brake fluids by the introduction of polyethylene glycol monomethyl ethers borates was studied. The use of these ethers as the main component of DOT-5.1 brake fluids was analyzed. 相似文献
8.
Laura Pistelli Rose Vanessa Bandeira Reidel Federico Parri Elisabetta Morelli Luisa Pistelli 《Natural product research》2019,33(1):143-147
The essential oil composition of three spontaneous species growing in an abandoned mining of Elba island was analyzed by GC–MS. A total of 194 compounds were identified representing 73.7–100% of the whole oil composition. The essential oils of Cistus salvifolius and Dittrichia viscosa from this site showed different profiles in comparison with those from not polluted area, where oxygenated sesquiterpenes were the main class. Volatiles from D. viscosa growing in ex-mining area presented 10-epi-γ-eudesmol and α-eudesmol as main compounds while β-caryophyllene and limonene were the main ones in not polluted area. Ambroxide and ambrial were the most important compounds in the essential oil from C. salvifolius harvested in polluted area while nonanal and tridecanal were the main compounds in control samples. Oxygenated monoterpenes were the most abundant class from both Lavandula stoechas samples, with fenchone and camphor as main compounds. 相似文献
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The synthesis and characterization of metal poly-yne polymers containing disilane, disiloxane and phosphine groups in the main chain are described. The platinum and palladium poly-yne polymers were synthesized by polycondensation reactions between a metal chloride and an α, ω-bisethynyl complex in amines in the presence of cuprous iodide as a catalyst. The nickel poly-yne polymers were synthesized by an alkynyl ligand exchange reaction between a nickel acetylide and an α, ω-bisethynyl complex in diethylamine in the presence of cuprous iodide as a catalyst. The reaction of the platinum poly-yne polymer, containing disiloxane groups in the main chain, with copper (I) salts afforded adducts of η-2-bonded σ-acetylide polymer complexes. The reactions of the palladium poly-yne polymer, containing phosphine groups in the main chain, with transition-metal carbonyl complexes afforded polymer complexes which have phosphorus in the main chain-transition-metal bonds. A concentrated solution of the platinum poly-yne polymer containing disiloxane groups in the main chain forms a lyotropic liquid crystal in dichloromethane or 1, 2-dichloroethane. 相似文献
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Combined semi-rigid homopolyesters, containing both main chain calamitic mesogens and one or two side chain azobenzene units separated by aliphatic (hexamethylene, octamethylene and decamethylene) chains in the polymer repeat units, were prepared and their liquid crystalline properties characterized. Polyesters having two side chain azobenzene units and a main chain biphenyl moiety showed a higher ordered smectic B or smectic F phase, whereas the other polymers containing a main chain 2,5-diphenyl-1,3,4-thiadiazole unit and one or two side chain methoxyazobenzene units formed a smectic C phase despite the presence of different mesogens in the main and side chains. This is probably due to the compact molecular chain-packing and intra- and intermolecular interactions between the polymer backbones and the two azobenzene units. 相似文献
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用气相色谱-质谱法对乙酰甲喹样品中的共存物进行定性、定量分析,确定样品中含有3种与乙酰甲喹结构类似的化合物,即3-甲基-2-乙酰基喹噁啉、3-甲基-2-乙酰基喹噁啉-4-氧化物、3-甲基-2-乙酰基喹噁啉-1-氧化物,其相对含量分别为4%、20%、30%,乙酰甲喹相对含量为46%。 相似文献
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Hiroaki Horiuchi Toru Fukushima Changli Zhao Tetsuo Okutsu Shoji Takigami Hiroshi Hiratsuka 《Journal of photochemistry and photobiology. A, Chemistry》2008,198(2-3):135-143
Conformational change of the main chain of poly(methylphenylsilane) functionalized with pendant azobenzene has been studied in the solution and in the film state. The conformation of the main chain was found to depend on the molar ratio of the Si units with and without the pendant azobenzene moiety. The inflection region for the conformational change was 0.3–0.5 of the molar ratio. The conformation of the main chain changed by the photoisomerization of the pendant azobenzene moiety in the film state. The efficiency of the conformational change of the main chain increased with the decrease of the molar ratio, accompanied by the highest final value of degree of the conformational change at the molar ratio of 0.5. The reverse conformational change was induced by heating. 相似文献
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V. I. Bol'shakova L. I. Demenkova V. A. Khan Zh. V. Dubovenko É. N. Shmidt V. A. Pentegova 《Chemistry of Natural Compounds》1985,21(6):749-752
The chemical composition of the oleoresin of the Kamchatka larch has been studied. Mono-, sesqui-, and diterpenoids have been found in it. The monoterpenes were represented by nine components (the main one being 3-carene), and among the sesquiterpene hydrocarbons γ-element, longifolene, and germacrene D predominated. The main oxygen-containing diterpenoid was larixyl acetate. Seven resin acids were determined, the main one being isopimaric and palustric and/or levopimaric. 相似文献
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Pd‐initiated polymerization of diazo compounds bearing dialkoxyphosphinyl group and hydrolysis of the resulting polymers and oligomers to afford phosphonic acid‐containing products 下载免费PDF全文
Hiroaki Shimomoto Akira Oda Motoki Kanayama Tomoya Sako Tomomichi Itoh Eiji Ihara Naohiro Hoshikawa Akihiko Koiwai Naoki Hasegawa 《Journal of polymer science. Part A, Polymer chemistry》2016,54(12):1742-1751
Pd‐initiated polymerization and oligomerization of diazo compounds containing a dialkoxyphosphinyl group are described. Polymerization of 2‐dialkoxyphosphinylethyl diazoacetates with π‐allylPdCl‐based initiating systems afforded C? C main chain polymers bearing phosphonate on each main chain carbon atom. The quantitative transformation of the side chain phosphonate to phosphonic acid resulted in the formation of water soluble polymers having the acid groups accumulated around their main chains, although the carbonyl ester linkage in the side chain was cleaved via intramolecular acid‐assisted hydrolysis in water at 80 °C. Pd‐initiated oligomerization of diethyl diazomethylphosphonate yielded an oligomeric product bearing diethoxyphosphiny groups directly attached to its main chain carbons, with unexpected incorporation of azo group in the main chain framework. Hydrolysis of the phosphonate of the oligomer afforded a water‐soluble product, which was revealed to show higher proton conductivity than poly(vinylphosphonic acid) under certain conditions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1742–1751 相似文献
15.
L. A. Serafimov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(10):1647-1657
The main heterogeneous equilibrium laws in multicomponent two-phase liquid-vapor systems and the main rules governing the
behavior of such systems and reported in 2002–2009 are considered from the point of view of modern concepts. 相似文献
16.
I.I. Konstantinov A.A. Sitnov V.S. Grebneva Y.B. Amerik 《European Polymer Journal》1983,19(4):327-331
Glass transition temperatures and thermodynamic parameters of mesophase melting of polymers with mesogenic side-groups of the phenyl benzoate class depend on the length of the alkoxy substitutent, the mobility of the mesogenic groups and the nature of the main chain. Polymers with mesogenic groups connected directly to the main chain, obtained by precipitation from solution, have equilibrium liquid crystalline structures in which the macromolecules exist in a compact coil conformation with an ordered arrangement of the mesogenic groups. The nature of the main chain of these polymers affects the liquid crystalline structure. Mesophase melting parameters of the polymers with mesogenic groups, connected by flexible spacer groups to the main chain, are almost independent of the thermal history of the samples. These polymers in the isotropic melts are assumed to contain aggregates of the mesogenic groups. 相似文献
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E. Ya. Beider A. A. Donskoi G. F. Zhelezina E. K. Kondrashov Yu. V. Sytyi E. G. Surnin 《Russian Journal of General Chemistry》2009,79(3):548-564
The main grades of fluorine-containing materials, including solid and powder materials, paint-and-lacquer coatings and films, organic glasses, rubbers and sealants used in aviation engineering are described in the paper. The main operating performances are given as well. 相似文献
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The reduction of carbon dioxide (CO2) is of interest to the chemical industry, as many synthetic materials can be derived from CO2. To help determine the reagents needed for the functionalization of carbon dioxide this experimental and computational study describes the reduction of CO2 to formate and CO with hydride, electron, and proton sources in the presence of sterically bulky Lewis acids and bases. The insertion of carbon dioxide into a main group hydride, generating a main group formate, was computed to be more thermodynamically favorable for more hydridic (reducing) main group hydrides. A ten kcal/mol increase in hydricity (more reducing) of a main group hydride resulted in a 35% increase in the main group hydride's ability to insert CO2 into the main group hydride bond. The resulting main group formate exhibited a hydricity (reducing ability) about 10% less than the respective main group hydride prior to CO2 insertion. Coordination of a second identical Lewis acid to a main group formate complex further reduced the hydricity by about another 20%. The addition of electrons to the CO2 adduct of tBu3P and B(C6F5)3 resulted in converting the sequestered CO2 molecule to CO. Reduction of the CO2 adduct of tBu3P and B(C6F5)3 with both electrons and protons resulted in only proton reduction. 相似文献