Syntheses of DL-threo-Thiamphenicol via Green Oxidation

IntroductionAqueous hydrogen peroxide is considered to be a“green”oxidant with a high oxidation efficiency due toits low molecular weight,cleanness in the oxidationprocess in which only harmless water is produced,lowcost of production and safe transport…     

Novel perfluoropolyethers containing 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole blocks: synthesis and characterization

Peroxidic perfluoropolyethers (PFPEs) are industrial intermediates used by Solvay Solexis for the preparation of different classes of (per)fluoropolyethers (Fomblin^®, Galden^®, Solvera^®, Fluorolink^®). The chemistry of these peroxidic compounds has been recently exploited for the synthesis of novel PFPE block copolymers. In the present work we report the synthesis, the structural and physical-chemical characterization of block copolymers obtained by the reaction of peroxidic PFPEs with 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, a cyclic homopolymerizable perfluoroolefin. These block copolymers combine the most attractive properties of the PFPEs, like the excellent lubrication, the high thermal stability and the optical transparency, with new specific properties which are related to the perfluorodioxolenic blocks.     

Analysis of hydrogen peroxide and an organic hydroperoxide via the electrocatalytic Fenton reaction

A new concept for the electrochemical detection of hydrogen peroxide, and organic hydroperoxides is presented. One advantage of the significance of this technique is that it does not require chemical modification of the electrode or addition of enzymes. Direct electro-reduction of the peroxides was not observed on the carbon disk electrode as it is a kinetically slow process. Redox cycling of the iron complex is apparent as Fe^IIEDTA rapidly reduces the O-O bond of the peroxides (Fenton Reaction) upon its production by the kinetically facile electro-reduction of Fe^IIIEDTA. This provides an enhanced and steady-state reductive current as observed by cyclic voltammetry. These features are indicative of the electrocatalytic (EC′) mechanism. A calibration curve was constructed based on the chronoamperometric response at 32 s and a detection limit for H₂O₂ and t-butyl hydroperoxide was calculated to be 0.4 μM and 20 µM, respectively. This difference is attributable to the rate in which the iron(II) complex reduces the O-O bond, H₂O₂ (2.3 × 10⁵ M^− 1 s^− 1) being faster than for the organic peroxide (5.1 × 10⁴ M^− 1 s^− 1). The Fe^IIEDTA complex was observed to be unreactive toward dialkyl peroxides. This method may find use in the detection of peroxide-based explosives or in enzymatic assays as it is rapid, simple, inexpensive and should prove to be robust.     

Fluorometry of hydrogen peroxide using oxidative decomposition of folic acid

Hydrogen peroxide (H₂O₂) is one of the most important reactive oxygen species. In the present study, a fluorometry method for detecting H₂O₂ utilizing folic acid was evaluated. Folic acid was decomposed by H₂O₂ in the presence of Cu(II) into pterine-6-carboxylic acid, leading to strong fluorescence enhancement. In the absence of the metal ion, superoxide and H₂O₂ could not decompose folic acid. Also, H₂O₂ plus sodium hypochlorite (a source of singlet oxygen) could not induce fluorescence enhancement. These results demonstrate that H₂O₂ can be selectively detected using folic acid plus Cu(II). The limit of detection (LOD; at S/N=3) for H₂O₂ is 0.5 μM. This method based on the fluorescence enhancement of folic acid was applied in order to determine small amounts of H₂O₂ generated through the autooxidation of semicarbazide (generation rate: ∼0.01 μM min⁻¹), a carcinogenic compound.      

Fluorinated monomer–styrene copolymer latex particles: I. kinetic studies in a soap-free aqueous medium

Soap-free emulsion copolymerization of 2, 2, 2-trifluoroethyl acrylate (3FEA) with styrene was carried out by using potassium persulfate as an initiator, and the effects of the weight fraction of 3FEA in the monomer feed on the kinetics and the particle size were investigated. Monomer conversions were followed by a gravimetric method, revealing that the overall polymerization rate increased exponentially with an increase in the weight fraction of 3FEA. According to dynamic light scattering measurement, the final particle size was found to decrease with an increase in the weight fraction of 3FEA. The number of particles for 3FEA homopolymerization was roughly twice as large as that at the fraction of 0.9, although both fractions had the almost same polymerization rates. These results indicate that soap-free emulsion homopolymerization of 3FEA would proceed not only inside the polymer particles but also in the aqueous phase throughout the polymerization.     

微波无极紫外光助双氧水处理活性艳红X-3B染料废水研究

活性艳红X-3B(C.I.ReactionRed 2)是一种单偶氮染料,其应用范围广泛,可用于棉、粘纤、涤/棉、锦纶、蚕丝、羊毛、锦/粘等织物的染色和丝绸的印花,因此其废水量大且色度深。目前染料废水的生物处理方法脱色效果差、占地面积大、处理周期长,传统的物理法和化学法也存在着成本高、不能彻底矿化染料分子等缺点。近年来发展起来的光化学处理染料废水的方法及各种光化学组合技术日益受到人们关注,但其中使用的普通紫外灯存在使用寿命短、启动慢、发光不稳定、电极材料易损等缺点[1],致使光化学方法处理废水的成本很高。本文利用微波产生的高频…     

钨酸钠与酸性离子液体催化醇的环境友好氧化反应

钨酸钠与酸性离子液体组成的催化体系可以催化双氧水进行醇的清洁氧化,反应在有机底物/水两相中进行.本体系在催化氧化仲醇为相应的酮时具有很好的活性;催化伯醇氧化时可以得到相应的醛、羧酸或两者的混合物.整个催化体系具有很好的重复利用性.     

Effect of iron salt on the color removal of water containing the azo-dye reactive blue 69 using photo-assisted Fe(II)/H2O2 and Fe(III)/H2O2 systems

The effect of chloride, sulfate and nitrate anions on the color removal of water containing the azo-dye reactive blue 69 (RB69) in acidic solution, by using photo-assisted Fenton process with Fe(II)/H₂O₂ and Fe(III)/H₂O₂ systems was investigated. Experiments were conducted in a batch reactor irradiated during 5 h with a domestic 15 W lamp with emission in the visible spectra. Experimental results showed color disappearance in the first 5 min of reaction in the photo-assisted process for all of the different salts, greatly enhancing the reaction rate with respect to the corresponding systems under dark conditions. The exception of the general trend was the Fe₂(SO₄)₃/H₂O₂/UV system, where the decolorization process is slower probably because the oxidative species generated by rupture of Fe(III)–peroxo complexes are less reactive. Total organic matter depletion and mineralization of the effluent were also tested during the experimental runs by means of total organic carbon (TOC) showing that, for most of the photo-assisted experiments high mineralization was reached after 3 h of reaction.     

A convenient one-pot synthesis of 2-(trifluoromethyl)-3,4,7,8-tetrahydro-2H-chromen-5(6H)-one derivatives and their further transformations

The trifluoromethyl containing heterocycles, 2-hydroxy-4-aryl-3-(thien-2-oyl)-2-(trifluoromethyl)-3,4,7,8-tetrahydro-2H-chromen-5(6H)-one derivatives 4, were synthesized via a one-pot three-component reaction of aldehyde 1 with 1,3-cyclohexanedione 2 and 4,4,4-trifluoro-1-(thien-2-yl)butane-1,3-dione 3 in the presence of a catalytic amount of Et₃N. The effect of bases and solvents on the reaction efficiency and yield was briefly investigated. Treatment of 4 with an excess amount of NH₄OAc in ethanol afforded 2-trifluoromethyl-1H-quinolin-5-one derivatives 5. Refluxing of 4 with TsOH in CHCl₃ gave the corresponding dehydrated products 8.     

One-pot synthesis of partially fluorinated naphthalene, anthracene, and chrysene derivatives

A series of partially fluorinated naphthalene, anthracene, and chrysene derivatives have been synthesized by a convenient one-pot reaction of multi-fluorinated aromatics and 1,4-dilithio-1,2,3,4-tetraaryl-1,3-butadiene that was generated in situ from the reduction of diphenylacetylene derivatives with lithium naphthalenide.