Oxidative cleavage of alkenes using an in situ generated iodonium ion with oxone as a terminal oxidant

A facile and operationally convenient catalytic procedure for oxidative cleavage of alkenes is described. In situ formed [hydroxy(4-carboxyphenyl)iodonium]ion, 2, from the oxidation of 4-iodobenzoic acid, 1, has been shown to facilitate the cleavage of a variety of alkenes in presence of Oxone as a co-oxidant. Optimization of the reaction conditions using 1-phenyl-1-cyclohexene, 3, and the competitive oxidative cleavage of different substrates using the optimized conditions has uncovered important mechanistic details of the reaction.     

Aerobic oxidation of alcohols using bismuth bromide as a catalyst

We developed an environmentally friendly method for aerobic oxidation of alcohols using a commercially available, relatively benign bismuth salt as a catalyst. We found that the catalytic combination of BiBr₃ with nitric acid is key for enhancing the reactivity. The reaction proceeds well under air, making the use of pure oxygen unnecessary. Each of the primary or secondary alcohols tested was oxidized to the corresponding aldehydes or ketones using this protocol.     

KTiOPO4单晶膜钾离子选择性电极的研究

本文采用KTiOPO4单晶薄片作为离子活性传感膜, 制备了钾离子选择性电极。20℃时, 其线性响应范围为1.2×10^-^5～1.0mol.dm^-^3氯化钾溶液, 平均响应斜率为58mV/-lgak, 对钠离子的电位选择性系数为4.0×10^-^4。该电极的优点是电极斜率受酸度变化影响小, 稳定性和重现性好, 寿命长。     

Electrochemical detection of the oxidation of alcohols byN-hydroxyethylethylenediamminetriacetatoruthenate(IV)

The oxidation of [Ru^III(hedta)(H₂O)]=(1) to its Ru^IV monomeric complex at a glassy carbon electrode is abserved to promote oxidation of alcohols bearing an a-hydrogen (i-PrOH benzyl alcohol,sec-phenethyl alcohol). Tertiary substitution blocks the oxidation (t-BuOH). The oxidation of the alcohols is detected by an enhancement in the current of the Ru^IV/III waves at potentials above 0.96V, caused by scavenging (reduction) of Ru^IV by the alcohols. Binuclear complexes which possess Ru^IV bridged by oxo to either a second Ru^IV or to Ru^III in species of composition [LRuORuL]ⁿ⁻, L=hedta³⁻, fail to oxidize the alcohols. The terminal oxo moiety attached to Ru^IV is postulated to facilitate the oxidation of primary and secondary alcohols in a manner analogous to Meyer's [RuO(trpy)(bpy)]²⁺ catalyst. The dissociation of the (III,IV) binuclear complex into its monomers provides a pathway which increases catalytic activity at the expense of the inactive (III, IV) binuclear complex's concentration. TMC 2531     

Microwave-assisted oxidation of alcohols using Magtrieve™

Primary and secondary alcohols can be selectively oxidized under microwave irradiation into the corresponding aldehydes and ketones within 5-30 min using commercially available and magnetically retrievable Magtrieve™.     

Shape-selective oxidation of primary alcohols using perruthenate-containing zeolites

Potassium perruthenate (KRuO4), a known, effective oxidant for the conversion of primary and secondary alcohols into carbonyl compounds is impregnated into zeolite X and shown to be a shape-selective oxidant using benzyl alcohol (reacted) and pyrenemethanol (not reacted).     

Electrochemical oxidation of alcohols: Part II preparative anodic oxidation of secondary alkanols employing lithium nitrate

The nitrate-mediated oxidation of simple alkanols to the corresponding ketones is described. Except for compounds containing several tertiary hydrogens the procedure is simple to perform and gives clean products in high current yield.     

Transition metal-free and substrate-selective oxidation of alcohols using water as an only solvent in the presence of β-cyclodextrin

A facile, substrate-selective and transition metal-free oxidation of benzylic and allylic alcohols catalyzed by β-cyclodextrin with NaOCl oxidant using water as an only solvent was developed.     

Chain ion molecular mechanism of ascorbic acid oxidation with hydrogen peroxide. Cu3+ ion as a chain carrier

The kinetics and mechanism of ascorbic acid (DH₂) oxidation have been studied under anaerobic conditions in the presence of Cu²⁺ ions. At 10^?4 ≤ [Cu²⁺]₀ < 10^?3M, 10^?3 ≤ [DH₂]₀ < 10^?2M, 10^?2 ≤ [H₂O₂] ≤ 0.1M, 3 ≤ pH < 4, the following expression for the initial rate of ascorbic acid oxidation was obtained: where χ₂ (25°C) = (6.5 ± 0.6) × 10^?3 sec^?1. The effective activation energy is E₂ = 25 ± 1 kcal/mol. The chain mechanism of the reaction was established by addition of Cu⁺ acceptors (allyl alcohol and acetonitrile). The rate of the catalytic reaction is related to the rate of Cu⁺ initiation in the Cu²⁺ reaction with ascorbic acid by the expression where C is a function of pH and of H₂O₂ concentration. The rate equation where k₁(25°C) = (5.3 ± 1) × 10³M^?1 sec^?1 is true for the steady-state catalytic reaction. The Cu⁺ ion and a species, which undergoes acid–base and unimolecular conversions at the chain propagation step, are involved in quadratic chain termination. Ethanol and terbutanol do not affect the rate of the chain reaction at concentrations up to ≈0.3M. When the Cu²⁺–DH₂–H₂O₂ system is irradiated with UV light (λ = 313 nm), the rate of ascorbic acid oxidation increases by the value of the rate of the photochemical reaction in the absence of the catalyst. Hydroxyl radicals are not formed during the interaction of Cu⁺ with H₂O₂, and the chain mechanism of catalytic oxidation of ascorbic acid is quantitatively described by the following scheme. Initiation: Propagation: Termination:      

Electrochemical oxidation of α-hyponitrate ion and its analytical applications

α-Hyponitrate ion is electrochemically oxidized at mercury electrodes: the reaction proceeds by an initial 1-electron oxidation to give an anion radical which decomposes to give nitrogen oxide and nitrite as the ultimate products. The d.c. polarographic wave of α-hyponitrate (E_{$\text{1}\text{2}$} = -0.325 V vs. SCE) in 0.1 M sodium hydroxide can be used for the determination of α-hyponitrate in the range 0.08–1.3 mM; a.c. polarography (E_p = -0.30 V vs. SCE) is useful in the range 0.075–1.0 mM. Amperometric titration with 0.05 M hexacyanoferrate(III) is suitable for determinations of 5–20 mg of sodium α-hyponitrate. A.c. polarography at pH 11.0 allows α-hyponitrate to be determined in the presence of 50-fold amounts of hydroxylamine.     

Metal-free oxidation of secondary benzylic alcohols using aqueous TBHP

We report a simple, yet efficient metal-free oxidation of secondary benzylic alcohols in the presence of t-butyl hydroperoxide (70% TBHP) with high yields of up to 98%. This type of reaction can be carried out using a wide variety of substrates, requires no other organic solvent, and proves to be tolerant toward a variety of different functional groups.     

Resorufin as an electron acceptor in glucose oxidase-catalyzed oxidation of glucose

Resorufin (1) has been found to act as an electron acceptor in glucose oxidase (GOD)-catalyzed oxidation of glucose. When a 1: 1: 1 mixture of solutions of 1 (5.0 microM), glucose, and GOD (4.0 mg/ml) in phosphate buffer (pH 7.4, 0.1 M) was incubated at 36 degrees C under aerobic conditions and the reaction was followed by a measurement of changes in fluorescence intensity due to 1, only two types of fluorometric traces were observed: (1) when a glucose solution of less than 0.7 mM was subjected to the enzymatic reaction, no consumption of 1 was observed; (2) the reaction with glucose at more than 1.0 mM always consumed 1, affording a regression fluorometric curve, and yet the obtained fluorometric traces could be almost superimposed on one another with no dependence on the glucose concentration. The reasons for the observed phenomena are discussed.     

Ruthenium-catalyzed oxidation of alcohols and catechols using t-butyl hydroperoxide

Ruthenium complexes catalyze the oxidation of alcohols to the corresponding ketones or aldehydes when t-BuOOH (70% aq.) is used as an oxidant. The reactions proceed at room temperature to give the products in excellent to fairly good yields. Among the transition metal catalysts used, dichlorotris(triphenylphosphine)ruthenium (RuCl₂(PPh₃)₃) showed the highest catalytic activity. 3,5-Di-t-butylcatechol and 4-t-butylcatechol are also effectively oxidized to the corresponding 1,2-benzoquinones in the presence of a catalytic amount of RuCl₂(PPh₃)₃ at room temperature with 1.1 equiv. of t-BuOOH, in quantitative yields. Hydrogen peroxide (30% aq.) can also be employed as an oxidant to give 1,2-benzoquinones in excellent yields.     

Resazurin as an electron acceptor in glucose oxidase-catalyzed oxidation of glucose

The behavior of resazurin (1) as an electron acceptor in glucose oxidase (GOD)-catalyzed oxidation of glucose under anaerobic conditions is described. When a mixture of 1, glucose, and GOD in phosphate buffer (pH 7.4, 0.1 M) was incubated at 25 degrees C, the resulting solution turned purple to fluorescent pink due to the deoxygenated product, resorufin (2). On incubation of 1 with GOD alone or with H2O2 under essentially the same conditions, no color change was seen, indicating that generation of 2 in the enzymatic reaction is brought about through reduction of 1 by the reduced form (GODred) of GOD, which was also supported by the voltammetric behavior of 1. However, it was found that the enzymatic transformation of 1 to 2 is of no practical use as an indicator reaction for glucose determination using only GOD due to a slow reaction of 1 with GODred. Based on a ping-pong type mechanism with a steady-state approximation, KM and kcat for 1 as an electron acceptor from GODred were estimated to be 15+/-1.3 microM and (5.0+/-0.5) x 10(-2) s(-1), respectively.     

Selective oxidation of aromatic primary alcohols to aldehydes using molybdenum acetylide oxo-peroxo complex as catalyst

Selective oxidation of various aromatic alcohols to aldehydes has been carried out with very high conversion (90%) and selectivity (90%) for aldehydes using cyclopentadienyl molybdenum acetylide complex, CpMo(CO)₃(CCPh) (1) as catalyst and hydrogen peroxide as environmentally benign oxidant. Water-soluble Mo acetylide oxo-peroxo species is formed in situ after reaction of 1 with aqueous hydrogen peroxide during the course of reaction as catalytically active species. Interestingly even though the catalyst is homogeneous it could be recycled very easily by separating the products in organic phase and catalyst in aqueous phase using separating funnel. Even after five recycles no appreciable loss in alcohol conversion and aldehyde selectivity was observed.     

Electrochemical studies of few-layered graphene as an anode material for Li ion batteries

Few-layered graphene (FLG) with specific surface area of only ~8.2 m² g^?1 was synthesized from graphene oxide (GO) using microwave-assisted exfoliation. GO was prepared using modified Hummers method. Few-layered nature of the exfoliated material was confirmed by electron microscopy, X-ray and electron diffraction, and Raman spectroscopy. Coin cells were fabricated using FLG as an anode and lithium metal as a counter electrode. The cells were tested using cyclic voltammetry and galvanostatic cycling techniques. FLG showed reversible capacity values of ~400 and ~250 mAh g^?1 at current rates of 0.1 and 1 C, respectively. Columbic efficiency was more than 98 % while cycle to cycle capacity fading was less than 2 %. Maximum discharge or charging capacity was below 0.3 V, a preferable characteristic for achieving ideal anodic behavior.