Effect of Quinones on the Cobalt(II) Acetate–Catalyzed Mild Oxidation of Cyclohexane with Hydrogen Peroxide in Acetic Acid

The effects of free-radical reaction inhibitors (InH), hydroquinone (HQ) and quinone (Q), on the oxidation of cyclohexane catalyzed by cobalt(II) acetate Co(OAc)₂ · 4H₂O and on the decomposition of hydrogen peroxide in acetic acid (HOAc) at 303 K were studied. It was found that an increase in the concentration of HQ in the starting reaction mixture containing cyclohexane, the catalyst, and H₂O₂ dissolved in HOAc resulted in an exponential decrease in the yields of the target products of oxidation: cyclohexanol, cyclohexanone, and cyclohexyl hydroperoxide. In the presence of Q, the dependence of the yield of the target products on the initial inhibitor concentration exhibited a maximum at (1.8–2.5) × 10^–2 M Q. At (2.2–2.4) × 10^–2 M Q concentrations, the yield of the target products was 55–60% of that in an uninhibited process. Based on kinetic, spectrometric, and quantum-chemical data, the effect found was explained by the fact that under the experimental conditions highly active hydroxyl derivatives of radicals rather than a hydroxy quinolide hydroperoxide (the homolysis of which can produce species with a free valence, which are capable of initiating free-radical reactions) were largely formed from Q.     

Studies on Phenol Oxidation with H2O2 Catalyzed by Schiff Base Cobalt(II) Complexes in Micellar Solution

The two Schiff base cobalt(II) complexes, CoL¹ and CoL², were synthesized and characterized. The metallomicelle made up of the cobalt(II) complexes and surfactants (CTAB, LSS and Brij35), as mimic peroxidase metalloenzyme, were used in the catalytic oxidation of phenol by H₂O₂. The mechanism and a kinetic mathematic model of the phenol catalytic oxidation were studied. The acid effect of reaction system, structural effect of the complexes, and effect of temperature on the rate of the phenol oxidation catalyzed by the mimetic peroxidases have been discussed. The results showed that the schiff base cobalt(II) complexes and their metallomicelles as peroxidase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme.     

壳聚糖固载的四苯基钴卟啉催化空气氧化环己烷

 将金属卟啉吸附固载到壳聚糖上,在室温下制备了壳聚糖四苯基钴卟啉催化剂,并用紫外光谱技术测定了四苯基钴卟啉的固载量. 在未加入任何溶剂和还原剂的条件下,研究了壳聚糖四苯基钴卟啉催化空气氧化环己烷的性能. 在418 K和0.8 MPa的空气压力下,壳聚糖四苯基钴卟啉能够很好地催化空气氧化环己烷,环己烷转化率为11%,相应的主产物环己醇和环己酮的选择性为87%,转化数为2.9×105,与未固载的四苯基钴卟啉相比,其催化性能大大提高,环己烷转化率和转化数分别提高了10倍和27倍. 研究结果表明: 壳聚糖对四苯基钴卟啉不仅有明显的保护作用,使之免遭氧化破坏,而且还有重要的助催化作用.     

Selective Aerobic Oxidation of Methylarenes to Benzaldehydes Catalyzed by N-Hydroxyphthalimide and Cobalt(II) Acetate in Hexafluoropropan-2-ol

Efficient and highly selective catalytic conditions for the aerobic autoxidation of methylarenes to benzaldehydes, based on N-hydroxyphthalimide (NHPI) and cobalt(II) acetate in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP), were developed. The sustainable conditions enable a multigram scale preparation of benzaldehyde derivatives in high efficiency and with excellent chemoselectivity (up to 99 % conversion and 98 % selectivity).     

Kinetics of the Acetic Acid Oxyethylation Catalyzed by Chromium Acetate

The effect of the product of the acetic acid oxyethylation (ethylene glycol monoacetate) on the kinetics of this reaction in the presence of chromium acetate is studied. Compared to base catalysis, catalysis with chromium acetate provided a higher selectivity in the formation of the monoaddition compound. It is found that an increase in the concentration of ethylene glycol monoacetate resulted in a drop in the reaction rate. The hypothetical mechanism of catalysis is proposed. The kinetic equation that adequately describes all experimental data is derived from this mechanism.     

Molybdovanadophosphoric Acid Catalyzed Oxidation of Hydrocarbons by H2O2 to Oxygenates

Heteropoly acids of the general formula H_3+x[PMo_12-xV_xO₄₀] (where x = 1,2,3) catalyzed the oxidation of aromatic hydrocarbons at 65°C with H₂O₂ to give oxygenated products. Among the catalysts, H₄[PMo₁₁VO₄₀] was found to be a more active catalyst and its activities have been reported in the oxidation of cyclohexane, methyl cyclohexane, naphthalene, 1-methyl naphthalene and biphenyl.     

The Mercury (II) Catalyzed,One-Pot Oxidation of Terminal Alkynes by Sodium Perborate in Acetic Acid

A series of terminal alkynes has been reacted with sodium perborate and mercuric acetate catalyst in acetic acid to produce 1-acetoxyalkan-2-ones in good yield. The reaction constitutes a mild and convenient method for the oxidation of terminal triple bonds.     

Water Oxidation Catalyzed by Cobalt(II) Adsorbed on Silica Nanoparticles

A novel, highly efficient, and stable water oxidation catalyst was prepared by a pH-controlled adsorption of Co(II) on ～10 nm diameter silica nanoparticles. A lower limit of ～300 s(-1) per cobalt atom for the catalyst turnover frequency in oxygen evolution was estimated, which attests to a very high catalytic activity. Electron microscopy revealed that cobalt is adsorbed on the SiO(2) nanoparticle surfaces as small (1-2 nm) clusters of Co(OH)(2). This catalyst is optically transparent over the entire UV-vis range and is thus suitable for mechanistic investigations by time-resolved spectroscopic techniques.     

Catalyzed Autoxidation of Hydrogensulfite by Cobalt(II) (2,3,9,10-tetramethyl-1,4,8,11-tetraaza-cyclotetradeca-1,3,8,10-tetraene) (H 2 O) 2 2+

The catalytic autoxidation of hydrogensulfite (hydrogentrioxosulfate(1-)) in the presence of Co(tim)(H 2 O) 2 2+ (tim=2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) was studied. Dioxygen reacts with excess sulfite in the presence of Co(tim)(H 2 O) 2 2+ in a complex process (a minimum of five kinetic steps can be identified) to produce Co(tim)(SO 3 ) x (3 m 2 x )+ ( x =1 or 2) ( u max at 350 nm) and sulfate. Seventy turnovers over 4 h were attained in a system where dioxygen and sulfite were supplied constantly. The Co(III) product formed reacts only slowly with dioxygen to produce sulfate. A mechanistic analysis of the results implies the involvement of a Co(tim)-dioxygen adduct, stabilized by an axial sulfite ligand.     

Selective Oxidation of Sulfides to Sulfoxides using H2O2 Catalyzed by p-Toluenesulfonic Acid (p-TsOH) Under Solvent-Free Conditions

Abstract

An efficient, chemoselective, and environmental friendly procedure for the oxidation of sulfides to sulfoxides is described. Various types of aromatic and aliphatic sulfides are selectively oxidized to sulfoxides in good to excellent yields using 30% H₂O₂ in the presence of catalytic amounts of a p-TsOH under solvent-free conditions at room temperature.     

wo3催化h2o2氧化环己酮合成己二酸

以WO3为催化剂,在无有机溶剂和相转移催化剂的情况下,用H2O2氧化环己酮合成己二酸。探讨了催化剂用量、H2O2用量、反应温度和时间等条件对反应的影响。在优化条件下:n(环己酮)∶n(H2O2)∶n(WO3)=100∶500∶2,反应温度为120℃,反应6 h,己二酸分离收率可达80.3%,纯度为99.8%;催化剂重复使用5次后己二酸收率仍可达70.2%。     

Liquid-Phase and Solventless Oxidation of Cyclohexane,Benzene, and Other Hydrocarbons by Cerium(IV) Catalyzed by Iridium(III) in Acidic Medium

Oxidation of some hydrocarbons dissolved in acetic acid by cerium(IV) sulphate at 100 °C in the presence of traces of iridium(III) chloride (catalyst-substrate 1:56818 to 151515) in the solution phase resulted in good to excellent yields of corresponding carbonyl compounds. In the cases of cyclohexane and benzene, 44% and 51.8% yields of corresponding carbonyl compounds were obtained, whereas in other cases, yield ranged from 34.9 to 99.8%. Yield decreased when reactions were performed in a microwave oven by adsorbing reactants (except acetic acid) on alumina. Decrease in the yield was probably due to the high temperature generated during the course of the reaction, resulting in the loss of organics from evaporation. Conditions were optimized for the highest yields under ambient conditions.     

Competition Between O2 and H2O2 in the Oxidation of Fe(II) in Natural Waters

The oxidation rates of nanomolar levels of Fe(II) in seawater (salinity S = 36.2) by mixtures of O₂ and H₂O₂ has been measured as a function of pH (5.8–8.4) and temperature (3–35∘C). A competition exists for the oxidation of Fe(II) in the presence of both O₂ (μ mol⋅L⁻¹ levels) and H₂O₂ (nmol⋅L⁻¹ levels). A kinetic model has been applied to explain the experimental results that considers the interactions of Fe(II) with the major ions in seawater. In the presence of both oxidants, the hydrolyzed Fe(II) species dominate the Fe(II) oxidation process between pH 6 and 8.5. Over pH range 6.2–7.9, the FeOH⁺ species are the most active, whereas above pH 7.9, the Fe(OH)⁰₂ species are the most active at the levels of CO²⁻₃ concentration present in seawater. The predicted Fe(II) oxidation rate at [Fe(II)]₀ = 30nmol⋅L⁻¹ and pH = 8.17 in the oxygen-saturated seawater with [H₂O₂]₀ = 50nmol⋅L⁻¹ (log ₁₀ k = −2.24s⁻¹) is in excellent agreement with the experimental value of log ₁₀ k = −2.29s⁻¹ ([H₂O₂]₀ = 55nmol⋅L⁻¹, pH = 8).     

四氯化锡催化乙酸异戊酯的合成

羧酸酯是重要的化工产品 ,其合成一直受到人们的关注 .它一般是利用羧酸、羧酸酐或酰氯与醇反应制得 ,羰基化制酯类近年也颇受重视 [1] .异戊醇是工业废料杂醇油的主要成份 ,如何合理利用是一个急需解决的问题 .一个方便的途径是使其与乙酸反应制备乙酸异戊酯 .乙酸异戊酯在香料、溶剂、萃取剂等方面都有广泛的应用 ,其传统合成方法是利用浓硫酸作为催化剂进行酯化反应 ,存在的缺点是对设备有严重的腐蚀、副产物较多、时间较长等 .四氯化锡作为高效的酯化催化剂引起了我们的注意 [2 ,3] .本文利用四氯化锡作为乙酸异戊酯的合成催化剂 ,在较…     

Selective Oxidation of Ethane to Acetic Acid Catalyzed by a C-Scorpionate Iron(II) Complex: A Homogeneous vs. Heterogeneous Comparison

The direct, one-pot oxidation of ethane to acetic acid was, for the first time, performed using a C-scorpionate complex anchored onto a magnetic core-shell support, the Fe₃O₄/TiO₂/[FeCl₂{κ³-HC(pz)₃}] composite. This catalytic system, where the magnetic catalyst is easily recovered and reused, is highly selective to the acetic acid synthesis. The performed green metrics calculations highlight the “greeness” of the new ethane oxidation procedure.     

钨磷酸催化H2O2氧化降解壳聚糖

钨磷酸催化H2O2氧化降解壳聚糖;壳聚糖;钨磷酸;H2O2;催化降解     

羟胺酸钴配合物催化对二甲苯氧化的研究

利用羟胺酸BPHA(N 苯甲酰基 N 苯基羟胺)钴配合物Co(BPHA)2作催化剂,对对二甲苯液相氧化反应进行了研究.详细考察了反应温度、催化剂浓度、配体浓度、反应时间和轴配体对该催化反应的影响.实验结果表明:当反应温度为125℃、氧气压力为0.5MPa、催化剂浓度为1.0×10-3mol/L、配体与催化剂的摩尔比为2∶1时、添加四甘醇或聚乙二醇作配体,反应2h时对二甲苯转化率可达41～43%、选择性为92%.本研究丰富了二甲苯选择性氧化的内容,并具有一定的工业应用前景.     

钴的羟胺酸类配合物催化对-二甲苯氧化反应研究

合成并表征了 3种羟胺酸类钴配合物 Co(OTPHA) 2 、Co(OTBHA) 2 和 Co(OTOHA) 2 ,并对比评价了它们催化对 -二甲苯均相液相氧化合成对 -甲基苯甲酸的活性和选择性 .考察了以纯氧为氧源 ,常压下反应温度、催化剂浓度、反应时间以及水对反应转化率和选择性的影响 .实验结果表明 ,不同分子结构的配体 ,可以通过其空间效应和电子效应对催化活性产生直接的影响 ,3种催化剂的活性顺序为 :Co(OTPHA) 2 >Co(OTBHA ) 2 >Co(OTOHA ) 2 .当反应温度为 110℃、催化剂浓度 1.0× 10 - 3mol/ L、反应 6 h时 ,催化剂 Co(OTPHA) 2 的对 -二甲苯转化率可达 33.9%、选择性为 86 .2 % .若提高反应温度和加大催化剂浓度 ,则会降低催化剂的活性 .反应中生成的水对氧化反应有抑制作用 ,应及时将反应中生成的水从体系中分出     

Oxidation Reaction of Phenol with H2O2 Catalyzed by Metallomicelles Made of Co(II) and Cu(II) Complexes of Imidazole Groups and Micelle as Mimic Peroxidase

The imidazole derivatives (N,N‐bis(2‐ethyl‐5‐methyl‐imidazole‐4‐ylmethyl) amino‐propane (biap)) and its complexes containing cobalt or copper ion were synthesized in this study. The oxidation reaction of phenol with oxidant H₂O₂ catalyzed by the metallomicelle made of the complexes of imidazole groups and micelle (CTAB, Brij35, LSS) as the mimetic peroxidase was studied. The results show that the reaction rate for the catalytic oxidation of phenol increases by a factor of approximately 1×10⁵ in the metallomicelle over that in the simple micelles or the pure buffer solution at pH=6.9 and 25°C. The catalytic effects changed with H₂O₂, temperature, pH, and surfactant kind in the catalytic reactive process are discussed. A kinetic mathematic model of the phenol oxidation catalyzed by the metallomicelle is proposed.