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1.
Liquid-phase oxidation of hydrocarbons in the presence of different types of phase-transfer reagents
The autoxidation of cyclohexene, tetralin and cumene was investigated in the presence of non-ionic, anionic and cationic surfactants and it was found that all three types of phase-transfer reagents are able to influence the rate of oxidation. If their HLB values are not too low (> 3) or not too high (< 15) all the non-ionic surfactants increase the rate of oxidation, otherwise they exert a slight inhibitory effect. If present in acid form, anionic surfactants all increase the rate of oxidation, while their Na-salts slightly inhibit the oxidation. Cationic surfactants all increase the autoxidation rate, but their catalytic efficiencies depend strongly on the experimental conditions. It was shown that the phosphonium ion-type surfactants are quickly oxidized by hydroperoxide present, but their catalytic and phase-transfer capabilities are not detectably reduced. In biphasic systems, the catalytic activities of cationic surfactants are strongly reduced by the presence of water as a separate phase. Light scattering measurements demonstrated that all three types of surfactants are prone to self-association when their concentrations are increased, and this limits their influence on the rate of oxidation. The oxidation rate is strongly reduced when non-ionizing but strongly solvating solvents are simultaneously applied in the reaction mixture. The rate-diminishing effect seems to correlate with the sequence of solvating ability of the solvents. It was pointed out that the presence of hydroperoxide is essential for the PTC-catalyzed oxidation of hydrocarbons. It is thought that the cationic and the anionic surfactants interact with the more nucleophilic (the inner one) and the more electrophilic (the outer one) O-atom of hydroperoxide, respectively, whereby homolysis of the O---O bond is facilitated. The non-ionic surfactants exert their rate-influencing effects through H-bond formation. In the PTC-catalyzed oxidation of hydrocarbons, the rate changes linearly only in a narrow range of PTC, hydroperoxide and substrate concentrations, and consequently the turnover number is not suitable to characterize the oxidation. 相似文献
2.
The retardation effect of oxygen and external magnetic field on the yield of radicals in hydroperoxide decomposition in catalytic nanoreactors was discovered. Mixed reverse micelles formed by the cationic surfactants (Surf) and hydroperoxide {mLOOH...nSurf} play the role of nanoreactors. Similar effects of oxygen and external magnetic field (60–150 mT) on the yield of radicals are observed in the catalytic decomposition of hydroperoxide in the presence of acetylcholine. It is noteworthy that the retardation effect of the magnetic field decreases in the presence of paramagnetic particles such as oxygen and relatively stable radicals. 相似文献
3.
N. A. Trunova D. A. Krugovov Yu. G. Bogdanova O. T. Kasaikina 《Moscow University Chemistry Bulletin》2008,63(4):214-218
The effect of the nature of the surfactant, peroxide (ROOH), and medium on the rate of radical initiation in a surfactant-ROOH mixed micellar system has been studied. Cationic surfactants, as distinct from anionic and nonionic ones, have been found to catalyze ROOH decomposition to form radicals. Cationic surfactants in an organic medium exhibit higher catalytic effect than in an aqueous solution. The catalytic activity of the surfactants is strongly dependent on the counterion nature. The highest catalytic activity is shown by cetyltrimethylammonium chloride. 相似文献
4.
O. T. Kasaikina N. V. Potapova D. A. Krugovov L. M. Pisarenko 《Kinetics and Catalysis》2017,58(5):556-562
The peculiarities of the catalytic action of cationic surfactants (CSurf) in combination with hydroperoxides on the generation of radicals and the influence of various factors on this process (transition metal compounds, oxygen, and external magnetic field) were considered. In the oxidized hydrocarbons (RH), hydroperoxides (ROOH), which are the primary amphiphilic products of oxidation, form mixed micelles {mROOH…nCSurf} with CSurf, in which fast decomposition of ROOH into radicals occurs and other polar components (metal compounds, inhibitors, etc.) can concentrate, which significantly affects the rate and mechanism of oxidation. The cationic surfactants immobilized on a solid support retain the ability to catalyze the decomposition of hydroperoxides, forming radicals, and to initiate radical oxidation and polymerization. It was found that acetylcholine, which is the most important neurotransmitter that plays an important role in the neuromuscular and cognitive activity of living beings, like cationic surfactants, catalyzes the radical decomposition of hydroperoxides in organic media, and the yield of radicals in this process decreases in a magnetic field and in the presence of oxygen. 相似文献
5.
Fluorescence quenching experiments indicate that energy transfer occurs from cumene excited at 254 nm to cumene hydroperoxide. Quantum yields show that the sensitized decomposition of the hydroperoxide occurs quantitatively and that 2-phenylpropanol-2 is the main photoproduct. In the presence of oxygen, this process plays a dominant role in the initiation of the photo-oxidation. When benzophenone is excited to the first triplet state by irradiation at 365 nm in the presence of cumene hydroperoxide, phosphorescence quenching experiments and laser flash photolysis suggest that an exciplex is formed. This exciplex dissociates into cumylperoxy and ketyl radicals in such a way that 80% of the excited ketone molecules are transformed into the corresponding pinacol. In the presence of oxygen, benzophenone primarily initiates the photo-oxidation of cumene by hydrogen abstraction but, as cumene hydroperoxide is formed, formation and reaction of the exciplex become progressively more and more important. The photochemical behaviour a fluorenone is quite different from that of benzophenone. The sensitized decomposition of cumene hydroperoxide occurs in the presence of that ketone. Surprisingly, fluorenone also initiates the photo-oxidation of cumene; the mechanism of that reaction is discussed. The whole set of results provides a sound basis for the interpretation of the photo-oxidation of polystyrene in various conditions. 相似文献
6.
4-Hydroxy-3-methyl-4′-benzeneazo(azobenzene) is used as an inhibitor to study the kinetics of radical generation upon cumyl
hydroperoxide or tert-butyl hydroperoxide decomposition in microemulsions formed in the presence of cationic surfactants in organic solvents and
on the surface of montmorillonite particles modified with cationic surfactants. It is demonstrated that, in contrast to microemulsions,
at comparable surfactant contents, modified montmorillonite has almost no effect on the decomposition rate of hydro-peroxides.
A considerable catalytic effect is only detected after Cu(2+) ions (≤0.1 wt %) are additionally applied onto the surface of
its nanoparticles. The addition of polar solvents dramatically decelerates the decomposition of hydroperoxides. The activation
energies of the reaction are determined for the dispersions of modified montmorillonite in toluene (56 kJ/mol) and toluene-ethanol
mixture (69 kJ/mol). 相似文献
7.
8.
丙烯环氧化钼—醇配合物催化剂的研究 总被引:3,自引:0,他引:3
合成了有机钼-醇配合物,并用IR和UV-Vis进行了表征。研究了对过氧化氢异丙苯(CHP)环氧化丙烯的催化性能。研究表明,合成的有机钼-醇化合物 具有较强的酸性,可分解CHP,在反应物中加入碱性抑制剂珂阻止CHP的分解;不同二醇制备的化合物,其要到性和氧化性能各不相同。由丙二醇制备的钼-醇化合物的催化环氧化性能较好。在醇/钼质量比为4、水含量低于10%(质量分数)、 酸量低于150mgKOH/mLcat.时,催化剂的性能基本相同。 相似文献
9.
The reactions of the copper (II) chelates of norephedrine (I), N-methylnorephedrine (II), N-ethylnorephedrine (III), and N-n-butylnorephedrine (IV) with benzoyl peroxide, cumene hydroperoxide, and 2,2′-diphenyl-1-picrylhydrazyl have been studied. Only the chelates of N-alkyl-substituted norephedrines enter into the reactions with free radicals, while their reactivity increases with the length of the alkyl substituent in the amino group of the ligand. The decomposition of cumene hydroperoxide was catalyzed by all four chelates; the catalytic efficiency increases in the order I<II<III < IV. 相似文献
10.
Electrocatalysis and amperometric detection of organic peroxides at modified carbon-paste electrodes
Cobalt-phthalocyanine modified carbon-paste electrodes are shown to catalyze the electro-oxidation of organic peroxides. Cyclic voltammetry offers useful insights into the catalytic behavior. Such behavior is exploited for developing an effective amperometric detection scheme for butanone peroxide, cumene hydroperoxide and tert-butyl hydroperoxide with optimum response at a potential of +0.70 V (vs. Ag/AgCl). Highly sensitive and stable flow injection measurements, with detection limits of 2.4-8.3 ng and relative standard deviations of 1.7-1.8% (n = 30), are reported. Applicability to measurements in drinking water is illustrated. 相似文献
11.
Farzaliev V. M. Allakhverdiev M. A. Shamkhalova S. A. Rzaeva I. A. 《Russian Journal of Applied Chemistry》2004,77(5):783-786
S-Substituted 2-mercapto-1,4-dihydroxybenzenes were prepared, and their antioxidative activity in autooxidation of cumene and in the reactions with cumylperoxy radicals and cumyl hydroperoxide was studied. 相似文献
12.
A. T. Guseinova K. I. Alieva I. A. Rzaeva A. M. Magerramov I. A. Aliev V. M. Farzaliev M. A. Allakhverdiev 《Russian Journal of Applied Chemistry》2009,82(9):1587-1591
1-Amino-4-phenyl-2-butanethiols were synthesized and characterized and their antioxidant activity in auto-oxidation of cumene
and in their reaction with cumyl peroxide radicals and cumyl hydroperoxide was studied. 相似文献
13.
Influence of Amine‐Based Cationic Gemini Surfactants on Catalytic Activity of α‐Chymotrypsin 下载免费PDF全文
Santosh Kumar Verma Bhupendra Kumar Ghritlahre Kallol K Ghosh Rameshwari Verma Shekhar Verma Xiujian Zhao 《国际化学动力学杂志》2016,48(12):779-784
The α‐chymotrypsin activity was tested in aqueous media with the presence of novel cationic amine–based gemini surfactant, with different spacer chain lengths and head group size, and also compared with the cationic cetyltrimethylammonium bromide (CTAB) and cetyltriphenylphosphonium bromide (CTPB) surfactants and aqueous buffer only. The p‐nitrophenyl acetate (PNPA) hydrolysis rate was monitored in the presence of the surfactant concentration at 30°C. Most of these gemini surfactants gave higher catalytic activity as compared to cationic CTAB and CTPB. The highest superactivity was measured in the presence of gemini 16‐12‐16, [dodecanediyl‐1,12‐bis(cetyldimethylammonium bromide)] surfactant at pH 7.5. The catalytic reaction follows the Michaelis–Menten mechanism. The catalytic rate constants, kcat, show the same profile that the catalytic affinity; KM being enhanced with increasing space chain length. The results are favorable for considering that the amine‐based gemini surfactant influences more than both the aqueous and cationic micellar media. 相似文献
14.
MinLI BinXU HuaCHEN HongJieZHENG XueYuanHUANG YaoZhongLI XianJunLI 《中国化学快报》2004,15(9):1022-1024
The promotion effect of cationic gemini surfactants for the hydroformylation of 1-dodecene in the organic/aqueous biphasic catalytic system is reported. The hydroformylation reaction in the presence of gemini surfactant occurred with higher turnover frequency and higher selectivity for linear aldehyde than using conventional monomeric surfactant CTAB. 相似文献
15.
Xiaolin Guo Xinpeng Zhao Dr. Xiongfei Luo Dr. Yulian Pang Prof. Dr. Bing Tian Prof. Dr. Shouxin Liu Prof. Dr. Shujun Li Prof. Dr. Jian Li Prof. Dr. Bernd Strehmel Prof. Dr. Zhijun Chen 《Angewandte Chemie (International ed. in English)》2023,62(27):e202301242
A sustainable photocatalyst for use with multiple purpose comprising demethylated lignin ( Fe3O4@D-wood ) was made by treatment of wood and iron oxide. Characterization followed by XRD, UV/Vis, photo-current studies, and electrochemical measurements. This material became subject of photocatalytic explorations for water treatment and material synthesis by radical photopolymerization. Exposure of Fe3O4@D-wood with artificial sunlight showed an improved activity considering photochemical oxidation of organic pollutants in the presence of H2O2. The efficient generation of reactive radicals brought this system also to photopolymerization. Here, radicals based on reactive oxygen species (ROS) generated in the catalytic cycle can be seen as the dominating species to initiate radical polymerization. A mixture of UDMA and TPGDA showed good reactivity with cumene hydroperoxide ( CHP ). Photocatalyst used for water treatment facilitates reuse for photopolymerization. 相似文献
16.
Erzsébet P. Gere Barna Bérczi Péter Simándi Gyula Wittmann András Dombi 《International journal of environmental analytical chemistry》2013,93(7):443-450
The kinetics of the reactions of H 2 O 2 and of methyl, ethyl, tert -butyl, and cumene hydroperoxides with I m were investigated in the presence and absence of molybdate as catalyst. These results were utilized to develop an analytical method for the simultaneous determination of H 2 O 2 and organic hydroperoxides in aqueous solutions. The total amount of H 2 O 2 and organic hydroperoxides can be determined by the spectrophotometric measurement of $ {\rm I}_3^ - $ formed quantitatively during 30 min of heating at 60°C. Catalase selectively decomposes H 2 O 2 in solutions containing organic hydroperoxides. The total amount of the latter can therefore be determined iodometrically after H 2 O 2 decomposition. In the oxidation of leuco crystal violet to crystal violet by H 2 O 2 and organic hydroperoxides, horseradish peroxidase exerts similar activities in the reactions involving methyl and ethyl hydroperoxides and H 2 O 2 , but its activity is much lower with tert -butyl and cumene hydroperoxide. It was observed that acetate buffer is unsuitable for pH adjustment in this type of hydroperoxide determination in consequence of the slow oxidation of the dye in the blank solution. 相似文献
17.
以 5,5-二甲基-1-吡咯啉-N-氧化物 (DMPO) 为自旋捕捉剂, 采用电子顺磁共振波谱 (EPR) 法研究了对氯四苯基锰卟啉 (T(p-Cl)PPMnⅢCl) 催化分解异丙苯过氧化氢 (CHP) 的反应过程. 结果表明, 在 25 oC 下的初始反应阶段, 在 T(p-Cl)PPMnⅢCl 与 CHP 的反应体系中仅检测到有异丙苯氧自由基的 DMPO 自旋加合物. 随着 CHP 浓度的增大, 还检测到有异丙苯过氧自由基自旋加合物的重排产物信号. 这说明在 T(p-Cl)PPMnⅢCl 的催化作用下, 初始阶段 CHP 是以 O–O 键均裂的方式产生异丙苯氧自由基引发分解反应, 并主要生成 2-苯基-2-丙醇. 在较大的初始 CHP 浓度下, 异丙苯氧自由基进一步与 CHP 反应, 产生异丙苯过氧自由基. 提出了 CHP 分解反应的主要自由基历程. 相似文献
18.
Polymer supported catalyst for the effective autoxidation of cumene to cumene hydroperoxide 总被引:2,自引:0,他引:2
The autoxidation of cumene to cumene hydroperoxide (CHP) in the presence of catalyst which was prepared by adsorbing copper(II) acetate onto polymer support, was investigated. When a styrene-divinylbenzene copolymer with sulfonic acid functional groups was used as a support, the resulting catalyst had no catalytic activity. When a macroreticular acrylic polymer containing carboxylic acid exchange groups was used as a support, an effective catalyst was obtained. In the presence of this catalyst (0.2 g Cu(OAc)2-BR-0.6 per 10 mL of cumene) at 353 K, the steady autoxidation rate is 84% faster than that initiated with CHP; the selectivity is 99% at 6.8% conversion. The catalyst is stable at 383 K. Furthermore, the catalyzed cumene autoxidation rate increases linearly with copper acetate loading as well as the amount of catalyst. But when the steady autoxidation rate increases, the selectivity to cumene hydroperoxide reduces, but is still satisfactory. Hence, it is possible to speed up the cumene autoxidation rate by raising the reaction temperature, using catalysts with high metal loading and using more catalyst. 相似文献
19.
环氧树脂的紫外光引发阳离子/自由基固化 总被引:2,自引:0,他引:2
研究了两类阳离子引发剂复合苯基硫钅翁盐和芳茂铁盐的紫外光引发活性以及它们分别与自由基引发剂的复合体系的增强光引发活性,并讨论了强氧化剂异丙苯过氧化氢对于芳茂铁盐引发效率的促进作用以及适量多元醇对于提高阳离子固化体系交联度所起的作用 相似文献
20.
G. Geuskens D. Baeyens-Volant G. Delaunois Q. Lu Vinh W. Piret C. David 《European Polymer Journal》1978,14(4):299-303
Decrease of the intensity of excimer fluorescence during the photo-oxidation of polystyrene indicates that energy transfer occurs from excited phenyl chromophores to oxidation products. Among these, hydroperoxide groups are prominent because, after acting as energy acceptors, they decompose efficiently into free radicals which initiate the photo-oxidation. This effect is clearly demonstrated using cumene hydroperoxide as a model compound for polystyrene hydroperoxides. It is concluded that the sensitized decomposition of hydroperoxide groups provides a general explanation for the characteristic kinetic behaviour of polymers in photo-oxidation as opposed to autoxidation. 相似文献