共查询到20条相似文献,搜索用时 184 毫秒
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本文报道2-环丙基-2-苯基六甲基三硅烷经光化学分解产生环丙基苯基硅烯(1)。1能与烯烃立体专一地进行加成,中间体硅杂环丙烷的醇解开环也是立体专一地顺式开环。 相似文献
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环丙烷基三甲基硅醚类化合物的脱硅基及酯化反应的研究 总被引:1,自引:0,他引:1
环丙烷基硅醚在卤化锌的作用下能够与硅胶反庆生成环丙基醇。研究了环丙烷基硅醚在卤化锌作用下与酰氯发生的酯化反应,发现在配位性较弱的溶剂二氯甲烷中,可得到比在乙醚中更高的产率。此外,采用一锅煮的方法,从烯醇硅醚出发,经过环丙化反应、酯化反应,以较好的产率合成了环丙基酯。 相似文献
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DUSY沸石催化α-蒎烯异构化的溶剂化效应 总被引:1,自引:0,他引:1
脱铝超稳Y沸石(简称DUSY)催化α 蒎烯异构化反应是固 液多相催化反应。α 蒎烯是松节油的主要成分,具有特殊的双环双键结构。DUSY是八面沸石经改性后的固体酸催化剂,它主要用于石油化学工业的精细化学品的合成。我们曾报道了DUSY沸石催化α 蒎烯的异构化反应及其动力学特征[1 3]。本文研究了脱铝超稳Y沸石(DUSY,SiO2/Al2O3=8 61)在介电常数不同的溶剂中催化α 蒎烯异构化反应,考察了在不同溶剂中,反应时间、温度对转化率、产物分布的影响。结果表明,采用介电常数较大的极性溶剂四氢呋喃,对反应更为有利。1 实验部分1 1 原料… 相似文献
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The mechanism of addition reactions of radicals formed during thermal decomposition of benzoyl peroxide with various chloro-substituted p-benzoquinones has been studied by the ESR technique in various solvents. The ESR spectra of the intermediate radicals show that addition occurs at the carbonyl oxygen. The important role of charge-transfer complexes in the reaction has been established. For strong CT complexes, the quinone molecule reacts with radicals derived from the solvent. 相似文献
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Bunyard WC Kadla JF DeYoung J DeSimone JM 《Journal of the American Chemical Society》2001,123(30):7199-7206
The thermal decomposition of the free-radical initiator bis(perfluoro-2-N-propoxyprionyl) peroxide (BPPP) was studied in dense carbon dioxide and a series of fluorinated solvents. For the fluorinated solvents, the observed first-order decomposition rate constants, k(obs), increased with decreasing solvent viscosity, suggesting a single-bond decomposition mechanism. The k(obs) values are comparatively larger in dense carbon dioxide and similar to the "zero-viscosity" rate constants extrapolated from the decomposition kinetics in the fluorinated solvents. The decomposition activation parameters demonstrate a compensation behavior of the activation enthalpy with the activation entropy upon change in solvent viscosity. Comparison of the change in activation parameter values upon change in solvent viscosity for BPPP with two additional initiators, acetyl peroxide (AP) and trifluoroacetyl peroxide (TFAP), further suggests that carbon dioxide exerts a very minimal influence on the decomposition mechanism of these initiators through solvent-cage effects. 相似文献
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The reaction between benzoyl peroxide and p-benzoquinone in concentrated solutions in a wide variety of solvents has been investigated by isolation and identification of the reaction products. Despite the high efficiency of p-benzoquinone as a trap for benzoyloxy radicals, partial decarboxylation to phenyl radicals usually occurs. Complete suppression of decarboxylation is achieved only when p-benzoquinone is present at such a high concentration that it is effectively the solvent for the reaction.The benzoyloxy- and phenyl semiquinones show marked differences in reactivity, the former tend to combine to form dibenzoyloxy dibenzoquinone while disproportionation is favoured by the latter to form quinhydrone of monophenylbenzoquinone.At lower quinone ratio, the peroxide undergoes induced decomposition by phenyl radicals both in “reactive” and “unreactive” solvents. The induced decomposition involves the formation of radical intermediates which undergo disproportionation, but not intramolecular rearrangement, to form p-phenylbenzoyloxy radicals. The latter can be captured, before undergoing decarboxylation, by the benzoyloxysemiquinones formed in the reaction.A correlation between the electron donating property of a radical and its capability to induce the decomposition of the peroxide was developed. 相似文献
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Mariángeles Iglesias Gastón P. Barreto Gladys N. Eyler Adriana I. Cañizo 《国际化学动力学杂志》2010,42(6):347-353
The thermal decomposition reaction of acetone cyclic triperoxide, acetone cyclic diperoxide, 4‐heptanone cyclic diperoxide, and pinacolone cyclic diperoxide ca. 0.02 M was studied in pure solvents (acetone and 1‐propanol) and in binary mixtures of acetone/1‐propanol at 150°C. The kinetics of each system was explored by gas chromatography (GC) at different solvent compositions. The reactions showed a behavior accordingly with a pseudo‐first‐order kinetic law up to at least 90% peroxide decomposition. The main organic products derived from these thermolysis reactions were detected by GC analysis. Among them, the corresponding ketones, methane, ethane, and propane were the main identified products. The rates of decomposition of pinacolone diperoxide in the pure solvents were practically independent of the solvent characteristics, so it was of no interest to analyze its kinetic behavior in binary solvent mixtures. In acetone/1‐propanol mixtures, the solvation effect on the cyclic peroxides derived from 4‐heptanone and acetone molecules was slightly dominated by specific interactions between 1‐propanol and a diradical‐activated complex initially formed. This species was preferentially solvated by 1‐propanol instead of acetone. Specific interactions between the O atoms from the peroxidic bond and the H from the OH in 1‐propanol can be taken into account. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 347–353, 2010 相似文献
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Product analysis of the thermolysis of allyl t-butyl peroxide in cyclohexane and tetrahydrofuran shows that an important induced decomposition of the peroxide occurs by the addition of radicals derived from the solvent, to the peroxide double bond, followed by an intramolecular homolytic displacement of the t-butoxyl group. Such a reaction is a 2,3-epoxypropanation of the solvent in which the initiator is decomposed. The reaction is shown to be general, by using other ethers and cycloalkanes as solvents. 相似文献
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Michel Julliard Myriam Scelles André Guillemonat Gaston Vernin Jacques Metzger 《Tetrahedron letters》1977,18(4):375-378
The photolysis of bis aryl-1,3 triazenes carried out in non-aromatic solvents gives products whose structures are consistent with a cage recombination process of homolytically formed radicals and the subsequent abstraction of hydrogen from the solvent molecules by these arylamino radicals.In aromatic solvents, a free-radical chain process leads to the formation of products resulting from the homolytic substitution on the solvent. 相似文献
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In hexamethylphosphoric triamide (HMPA), four representative diacyl peroxides, namely, benzoyl peroxide (1), Cyclopropylformyl peroxide (2), lauroyl peroxide (3) and trifluoroacetyl peroxide (4), all decompose at rates much higher than those expected from their unimolecular thermal decomposition, and the corresponding carboxylic acids are formed in high yields (74–97%). Furthermore, several radical colligation products formed from HMPA molecules can be identified. Evidently, the initial step in the reaction between a diacyl peroxide and the “solvent” HMPA involves an electron transfer with the latter acting as the donor. 相似文献
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Finding suitable solvents remains one of the most elusive challenges in rechargeable, nonaqueous Li-air battery technology. Although ether and amides are identified as stable classes of aprotic solvents against nucleophilic attack by superoxide, many of them are prone to autoxidation under oxygen atmosphere. In this work, we use density functional theory calculations coupled with an implicit solvent model to investigate the autoxidative stability of ether- and N,N-dialkylamide-based solvents. The change in the activation free energy for the C-H bond cleavage by O(2) is consistent with the extent of peroxide production for each class of solvent. Conversely, the thermodynamic stability alone is not sufficient to account for the observed variation in solvent reactivity toward O(2). A detailed understanding of the factors influencing the autoxidative stability provides several strategies for designing molecules with enhanced air/O(2) stability, comparable or superior to that of structurally related hydrocarbons. The mechanism of superoxide-mediated oxidation of hydroperoxides derived from ethers and amides is presented. The degradation mechanism accounts for the primary decomposition products (esters and carboxylates) observed in the Li-air battery with ether-based electrolytes. The identification of solvents having resistance to autoxidation is critical for the development of rechargeable Li-air batteries with long cycle life. 相似文献
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Vakrat-Haglili Y Weiner L Brumfeld V Brandis A Salomon Y McLlroy B Wilson BC Pawlak A Rozanowska M Sarna T Scherz A 《Journal of the American Chemical Society》2005,127(17):6487-6497
Generation of reactive oxygen species (ROS) is the hallmark of important biological processes and photodynamic therapy (PDT), where ROS production results from in situ illumination of certain dyes. Here we test the hypothesis that the yield, fate, and efficacy of the species evolved highly depend on the dye's environment. We show that Pd-bacteriopheophorbide (Pd-Bpheid), a useful reagent for vascular targeted PDT (VTP) of solid tumors, which has recently entered into phase II clinical trials under the code name WST09 (trade name TOOKAD), forms appreciable amounts of hydroxyl radicals, superoxide radicals, and probably hydrogen peroxide in aqueous medium but not in organic solvents where singlet oxygen almost exclusively forms. Evidence is provided by pico- and nanosecond time-resolved spectroscopies, ESR spectroscopy with spin-traps, time-resolved singlet oxygen phosphorescence, and chemical product analysis. The quantum yield for singlet oxygen formation falls from approximately 1 in organic solvents to approximately 0.5 in membrane-like systems (micelles or liposomes), where superoxide and hydroxyl radicals form at a minimal quantum yield of 0.1%. Analysis of photochemical products suggests that the formation of oxygen radicals involves both electron and proton transfer from (3)Pd-Bpheid at the membrane/water interface to a colliding oxygen molecule, consequently forming superoxide, then hydrogen peroxide, and finally hydroxyl radicals, with no need for metal catalysis. The ability of bacteriochlorophyll (Bchl) derivatives to form such radicals upon excitation at the near infrared (NIR) domain opens new avenues in PDT and research of redox regulation in animals and plants. 相似文献
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Sakamoto M Cai X Fujitsuka M Majima T 《The journal of physical chemistry. A》2006,110(42):11800-11808
The solvent effects on ketyl radicals of benzophenone derivatives (BPD) in the excited state (BPDH*(D1)) were investigated. Absorption and fluorescence spectra of BPDH*(D1) in various solvents were measured using nanosecond-picosecond two-color two-laser flash photolysis. The fluorescence peaks from BPDH*(D1) showed a shift due to the dipole-dipole interaction with the solvent molecules. The dipole moments (mu(e)) of BPDH*(D1) were estimated to be 7-10 D, indicating that BPDH*(D1) are highly polarized. It was revealed that the fluorescence lifetime (tau(f)) depends on mu(e) in acetonitrile because the stabilization by solvent molecules affects the tau(f) value in polar solvents, predominantly. On the contrary, the conformation of BPDH*(D1) plays an important role in cyclohexane because the efficiency of the unimolecular reaction from BPDH*(D1) depends on the conformation. The substituent effect on the electron transfer from BPDH*(D1) to their parent molecules was also discussed. 相似文献