Access to Nitriles from Aldehydes Mediated by an Oxoammonium Salt

A scalable, high yielding, rapid route to access an array of nitriles from aldehydes mediated by an oxoammonium salt (4‐acetylamino‐2,2,6,6‐tetramethylpiperidine‐1‐oxoammonium tetrafluoroborate) and hexamethyldisilazane (HMDS) as an ammonia surrogate has been developed. The reaction likely involves two distinct chemical transformations: reversible silyl‐imine formation between HMDS and an aldehyde, followed by oxidation mediated by the oxoammonium salt and desilylation to furnish a nitrile. The spent oxidant can be easily recovered and used to regenerate the oxoammonium salt oxidant.     

水解胶原蛋白热氧化及CaSO4形成机理探讨

水解胶原蛋白热氧化及CaSO4形成机理探讨;水解胶原蛋白; L-抗坏血酸; H2O2; 热氧化; CaSO4     

电催化氧化技术处理苯酚废水研究

电化学氧化法可有效处理挥发酚类废水,而阳极材料性能直接制约其电氧化效率.本文分别针对不锈钢、柔性石墨和SnO2 /Ti复合材料测定了其析氧过电位,并以不锈钢、柔性石墨为阳极材料,在 5~6V直流电压下,对合成苯酚废水进行了电化学氧化处理.结果表明:析氧过电位次序为SnO2 /Ti>柔性石墨 >不锈钢,处理后水的COD值接近或小于 100mg·L-1,且出水的苯酚浓度小于 0. 5mg·L-1.     

Nickel electrode modified by N,N-<Emphasis Type="Italic">bis</Emphasis>(salicylidene)phenylenediamine (Salophen) as a catalyst for methanol oxidation in alkaline medium

The electrocatalytic oxidation of methanol studied at the surface of nickel disc electrode coated with N,N-bis(salicylidene)phenylenediamine (Salophen) legend in 0.10 M NaOH solution using cyclic voltammetry. The results showed that the Ni-salophen layer formed at the surface of electrode behaves as an efficient electrocatalyst for the oxidation of methanol in alkaline medium. The thermal analysis of Ni-salophen complex studied at temperature ranges 0–800°C in argon atmosphere. Also, FTIR was employed to prove the formation of complex on the modified electrode surface. Moreover, the effects of various parameters such as oven temperature, methanol concentration, NaOH concentration and media temperature on electro-oxidation of methanol were investigated. The kinetic parameters such as activation energy and Tafel slope were calculated for methanol oxidation on the modified electrode surface. Published in Elektrokhimiya in Russian, 2009,, 2009, Vol. 45, No. 2, pp. 203–210. The text was submitted by author in English.     

Influence of the conditions of manufacture of nanomeric zirconium dioxide,stabilized with yttrium oxide,on its catalytic properties in the oxidation of CO

The morphological and catalytic properties of samples of nanomeric zirconium dioxide, stabilized with yttrium oxide, manufactured via the effect of a UHF field during the process of drying precipitated zirconium hydroxide and calcination at temperatures from 300 to 1000 °C, were studied. It was shown that the highest activity in the oxidation of CO occurred with 40 nm particles of zirconium dioxide prepared at 1000 °C. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 2, pp. 96–101, March–April, 2007.     

Catalytic activity and stability of anionic and cationic water soluble cobalt(II) tetraarylporphyrin complexes in the oxidation of 2-mercaptoethanol by molecular oxygen

The catalytic activity and stability of anionic cobalt(II) porphyrin complexes: 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrinatocobalt(II), 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5disulfonatophenyl)porphyrinatocobalt(II) and the cationic cobalt(II) porphyrin: 5,10,15,20-tetrakis[4-(diethylmethylammonio)phenyl]porphyrinatocobalt(II) tertraiodide have been investigated in the oxidation of 2-mercaptoethanol by dioxygen. All complexes were efficient catalysts for the auto-oxidation of 2-mercaptoethanol. The cationic cobalt(II) porphyrin has been found to be the most reactive catalyst. The rate of auto-oxidation of 2-mercaptoethanol catalysed by 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5disulfonatophenyl)porphyrinatocobalt(II) has been found to increase with increasing the pH from 7 to 9 then decreased at higher pH. The rate constants of auto-oxidation reaction showed linear dependence on catalyst concentration and saturation kinetics in both 2-mercaptoethanol concentrations and dioxygen pressure. Anionic cobalt(II) porphyrin complexes showed higher stability than the cationic catalyst in repeat oxidation reactions. Immobilizing the anionic catalysts on ion exchange resin and supporting the cationic catalyst on clay mineral montmorillonite improved their stabilities towards oxidation.     

Electrocatalytic oxidation of phytohormone salicylic acid at copper nanoparticles-modified gold electrode and its detection in oilseed rape infected with fungal pathogen Sclerotinia sclerotiorum

Salicylic acid (SA) is a biological substance that acts as a phytohormone and plays an important role in signal transduction in plants. It is important to accurately and sensitively detect SA levels. A gold electrode modified with copper nanoparticles was used to assay the electrocatalytic oxidation of salicylic acid. It was found that the electrochemical behavior of salicylic acid was greatly improved at copper nanoparticles, indicating that anodic oxidation could be catalyzed at copper nanoparticles. And the pH had remarkable effect on the electrochemical process, a very well-defined oxidation peak appeared at pH 13.3 (0.2 M NaOH). The kinetics parameters of this process were calculated and the heterogeneous electron transfer rate constant (k) was determined to be 1.34 × 10⁻³ cm s⁻¹, and (1 − α)n_α was 1.22. The gold electrode modified with copper nanoparticles could detect SA at a higher sensitivity than common electrodes. The electrode was used to detect the SA levels in oilseed rape infected with the fungal pathogen Sclerotinia sclerotiorum. The results showed that the SA concentration reached a maximum during the 10th-25th hours after infection. This result was very similar to that determined by HPLC, indicating that the gold electrodes modified with copper nanoparticles could be used as salicylic acid sensors.     

A Single-Atom Manipulation Approach for Synthesis of Atomically Mixed Nanoalloys as Efficient Catalysts

Synthesis of well-defined atomically mixed alloy nanoparticles on desired substrates is an ultimate goal for their practical application. Herein we report a general approach for preparing atomically mixed AuPt, AuPd, PtPd, AuPtPd NAs(nanoalloys) through single-atom level manipulation. By utilizing the ubiquitous tendency of aggregation of single atoms into nanoparticles at elevated temperatures, we have synthesized nanoalloys on a solid solvent with CeO₂ as a carrier and transition-metal single atoms as an intermediate state. The supported nanoalloys/CeO₂ with ultra-low noble metal content (containing 0.2 wt % Au and 0.2 wt % Pt) exhibit enhanced catalytic performance towards complete CO oxidation at room temperature and remarkable thermostability. This work provides a general strategy for facile and rapid synthesis of well-defined atomically mixed nanoalloys that can be applied for a range of emerging techniques.     

Oxidations by a H2O2-VO3 −-pyrazine-2-carboxylic acid reagent

Alkanes (cyclohexane, hexane, heptane isomers) are effectively oxidized in CH₃CN at 20–70°C by hydrogen peroxide when catalyzed by a Bu₄NVO₃-pyrazine-2-carboxylic acid system. Alkyl hydroperoxide is the main product; an alcohol and a ketone or an aldehyde are also formed. Under these conditions benzene is oxidized to give phenol, while alkyl benzenes yield oxygenation products both of the ring and the side chain. It has been assumed that the interaction of H₂O₂ with VO₃ ^– gives rise to generation of HO radicals and other radical-like vanadium containing species that abstract a hydrogen atom from an alkane, RH. The radical R^. formed reacts with O₂ to produce ROO^. which is then transformed to alkyl hydroperoxide.Presented at the VIII International Symposium on Homogeneous Catalysis (Amsterdam, 1992).Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 64–68, January, 1993.     

Preparation, Electrochemical Behavior and Electrocatalytic Activity of a Copper Hexacyanoferrate Modified Ceramic Carbon Electrode

A copper hexacyanoferrate modified ceramic carbon electrode （CuHCF/CCE） had been prepared by two-step sol-gel technique and characterized using electrochemical methods. The resulting modified electrode showed a pair of well-defined surface waves in the potential range of 0.40 to 1.0 V with the formal potential of 0.682 V （vs. SCE） in 0.050 mol·dm^-3 HOAc-NaOAc buffer containing 0.30 mol·dm^-3 KCl. The charge transfer coefficient （a） and charge transfer rate constant （ks） for the modified electrode were calculated. The electrocatalytic activity of this modified electrode to hydrazine was also investigated, and chronoamperometry was exploited to conveniently determine the diffusion coefficient （D） of hydrazine in solution and the catalytic rate constant （kcat）. Finally, hydrazine was determined with amperometry using the resulting modified electrode. The calibration plot for hydrazine determination was linear in 3.0 × 10^-6--7.5 × 10^-4 mol·dm^-3 with the detection limit of 8.0 × 10^-7 molodm^-3. This modified electrode had some advantages over the modified film electrodes constructed by the conventional methods, such as renewable surface, good long-term stability, excellent catalytic activity and short response time to hydrazine.