Simulation of the nonbranched-chain addition of saturated free radicals to alkenes and their derivatives yielding 1: 1 adducts

A reaction scheme is suggested for the initiated addition process. The scheme includes the reaction between the free 1: 1 adduct radical and the unsaturated reactant, which is in competition with chain propagation through a reactive free radical (\({}^ \cdot P{\mathbf{ }}Cl_2 ,(CH_3 )_2 \mathop C\limits^\cdot {\mathbf{ }}OH\), etc.) and yields a low-reactivity free radical (\(CH_2 = C(CH_3 )\mathop C\limits^\cdot {\mathbf{ }}H_2 ,{\mathbf{ }}CH_2 = CH\mathop C\limits^\cdot {\mathbf{ }}HOH\), etc.) inhibiting the nonbranched-chain process. Simple rate equations containing one to three parameters to be determined directly are set up using quasi-steady-state treatment. These equations provide good fits for the nonmonotonic (peaking) dependences of the formation rates of the molecular addition products (1: 1 adducts) on the concentration of the unsaturated component in liquid homogeneous binary systems consisting of a saturated component (PCl₃, 2-propanol, etc.) and an unsaturated component (methylpropene, 2-propen-1-ol, etc.). The unsaturated compound in these systems is both a reactant and an autoinhibitor generating low-reactivity free radicals.     

Using terahertz radiation to detect OH radicals and NO molecules in flames

The possibility of detecting OH radicals and stable paramagnetic NO species in flames using the effect of rotation of the polarization plane of terahertz radiation (1–10 THz) in a magnetic field (Faraday effect) was experimentally demonstrated. Experimental data on detection of NO in a cell and OH radicals in an atmospheric-pressure H₂/O₂/N₂ flame using this method are given. The proposed method can be used to study highly scattering media which are opaque in the visible region, for example, dusty or sooty flames.     

Electrochemical oxidation of toluene promoted by OH radicals

Benzaldehyde can be produced from toluene by an electrochemical process involving OH radicals. In the cathodic compartment of the electrolytic cell the reduction of molecular O₂ and of a metal ion M^ox, are simultaneously carried out in the presence of a toluene suspension. M^ox is the oxidized form of a redox couple such as V(V)/V(IV), V(IV)/V(III), Cu(II)/Cu(I); the electrogenerated H₂O₂ and the reduced metal ion generates OH radicals and M^ox, which is converted back to the reduced form at the electrode. The reactivity of the redox couples examined were compared from the point of view of their effectiveness for the toluene oxidation process. In some cases, current yields very close to the theoretical ones could be obtained.     

Electrochemical production of OH. radicals and their reaction with toluene

The reaction between electrochemically generated Fenton's reagent and toluene was studied. The products arising from this reaction system were consistent with a primary hydrogen atom abstraction from the methyl group of toluene to give benzyl radicals.Benzaldehyde was obtained with a current yield higher than 60%; benzyl alcohol was also produced in smaller quantities in some experiments. The dependence of the yields on reagent concentrations, temperature and coulombs passed was examined. On the basis of the experimental results a mechanism is proposed involving peroxy and alkoxy radicals as intermediates.     

Electrochemical oxidation of aliphatic hydrocarbons promoted by inorganic radicals. I. OH radicals

The OH initiated oxidation of aliphatic hydrocarbons by the simultaneous electrochemical reduction of O₂ and of Fe(III) at controlled potential was investigated in the liquid phase over a Fe(III) concentration range 0.5–5 mM. OH radicals were generated by the reaction: Fe(II)+H₂O₂Fe(III)+^.OH+OH^– The compounds studied were the linear alkane hydrocarbons from C₅ to C₁₀ and 3-methyl pentane. The results showed that the ketones are the only reaction products and that the yields decrease with increasing number of carbonium atoms of the hydrocarbon. Decreasing yields were also observed with increasing Fe(III) concentration.     

Oxidation of polymethylated benzenes promoted by.OH radicals

OH radicals, produced in aqueous acid media by the electrogenerated system Fe(II)/H₂O₂, promote the oxidation of polymethylated benzenes. Under our experimental conditions only one -CH₃ group was oxidized to -CHO. A reduction of aldehyde to alcohol by^.OOH radicals was shown to occur when H₂O₂ was produced in excess over Fe(II). In hydrochloric acid or in perchloric acid with Cl^– ions added, a remarkable increase of the yields was observed. The results are discussed on the basis of the kinetic parameters of the reactions involved in the process.     

Nanocatalysis production of photoactive radicals

Eosin Y (EY) dye can be reduced electrochemically by accepting either one or two electrons. The stable two electron reduction product of EY is also obtained by sodium borohydride (BH) reduction. Although the one- and two-electron reductions have similar potentials (− 1.03 and − 1.04 V, respectively), gold nanocatalysts change the traditional reduction reaction pathway of EY dye with BH to a selective one-electron reduction instead of two. The resultant one-electron reduction product is a slightly persistent semiquinone intermediate: the same as is produced with the electrochemical one-electron reduction. This is the first example of nanocatalysts guiding a reaction to the same products as the electrochemical pathway. The semiquinone intermediate was found to be photochemically active and decomposed by light into a novel green EY dye after losing two bromine atoms. Whereas in the dark, the semiquinone intermediate radical was found to be reduced by accepting another electron forming a colorless reduced form of EY. It was found that hollow gold nanoparticles were superior catalysts for this reaction than solid gold nanoparticles; this was attributed to the cage effect of hollow nanoparticles. This kind of powerful catalyst induced product specificity will be useful for the synthesis of novel molecules or improving the yield of existing products.     

Spin trapping study on addition reaction of organic radicals to methyl methacrylate and methyl tiglate

Summary The addition reaction of the radicals formed from 2,2zobisisobutyronitrile(AIBN), diisopropyloxydicarbonate(DISOP), or benzoyl peroxide(BPO) to methyl methacrylate--d₂(MMA--d₂) or methyl tiglate(MTA) has been investigated at 30°C by the spin trapping technique. The tail and head addition of the radicals were detected for MMA--d₂, and only the tail addition was observed for MTA.     

Theoretical kinetic study of the reaction between dimethyl disulfide and OH radicals

The potential energy profile of the reaction between dimethyl disulfide and OH^? radicals is explored by utilizing ab initio and hybrid meta density functional theory methods. Having the energies and structural data of the stationary points, statistical rate theories, such as transition state theory and variable reaction coordinate-transition state theory, are employed to compute the overall rate constants, and discuss the mechanism and product channels. On the basis of the calculations, the overall rate coefficient is predicted to be 2.49?×?10^?10?cm³?molecule^?1?s^?1 at 298?K. It is found that in the most favorable pathway, the reaction proceeds via formation of the relatively unstable intermediate CH₃S^?(OH)SCH₃ decomposing rapidly to yield CH₃S^?+CH₃SOH.     

Iodoazide addition to olefinic esters and their reaction with methanolic KOH

Addition of iodine azide to methyl 10-undecenoate (1), methyl oleate/elaidate (III,IV) and methyltrans-2-hexadecenoate (VII) yielded methyl 10-azido-11-iodoundecanoate (II, ∼ 100%), methylerythro/threo-9(10)-azido-10(9)-iodooctadecanoate (V,VI) and methylerythro-3-azido-2-iodohexadecanoate (VIII), respectively. The reaction of iodoazide adduct (II) with methanolic KOH yielded 10-azidoundec-10-enic acid (IX) and 10-oxoundecanic acid (X), while V and VI gave a mixture of 9(10)-oxooctadecanoic acid (XI). Adduct VIII, under the identical condition after esterification, gave 3 products, methyl 4-methoxy-trans-2-hexadecenoate (XII), 2-oxopentadecane (XIII) and methyl 3-methoxyhexadecanoate (XIV). The unusual behavior of VIII can be tentatively attributed to the role of adjacent carbonyl on the expected elimination of HI by methanolic alkali.     

Evaluation of sulphonated by-products of dodecyl benzene production

Light and heavy alkylated benzene accumulated as by-products during dodecyl benzene production were studied. The chemical structures of these by-products were established via various spectroscopy and chromatography techniques. Results showed their suitability for sulphonation and formulation of liquid surfactants. The light by-product, with its high eicosyl benzene content and likely orthosulphonation, was used satisfactorily to formulate wetting agents and emulsifiers. On the other hand, the heavy alkylated benzene was found to contain a high percentage of C₁₂-C₁₈ branched side chains. Surfactants formulated from it gave high detergency power and can be recommended for heavy duty applications.     

Lipids fromPlasmodium vinckei-infected erythrocytes and their susceptibility to oxidative damage

The constituent lipids of plasma and red blood cells (RBC) from mice late in infection with the malarial parasitePlasmodium vinckei were analyzed and compared with those obtained from uninfected animals. On a dry weight basis, the total extractable lipids of RBC increased three-fold during infection, while those of the plasma did not change significantly. In general, changes in individual plasma lipid constituents paralleled those found in RBC of infected mice but were of smaller magnitude. While the increase in the total lipids of parasitized RBC was largely attributable to an increase of more than fourfold in total phospholipids, a significant increase in neutral lipids was also observed. Phosphatidylcholine and phosphatidylethanolamine were the major phospholipids present within RBC, and their total and relative concentrations increased as a result of the infection. A parallel increase occurred in the ratio of unsaturated to saturated fatty acids in the parasitized RBC phospholipids. Infection was also associated with decreases in the relative amount of cholesterol present in RBC and in the ratio of cholesterol to phospholipid. Consistent with this, the fluorescence polarization of 1[4-(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene within parasitized RBC plasma membranes was decreased in comparison with its value in noninfected RBC, indicating that malarial infection decreases the “order” of membrane lipids. These modifications, in conjunction with the increased levels of vitamin E and malonyldialdehyde reported elsewhere, are important determinants of the susceptibility of the different membrane compartments within infected RBC to peroxidative damage.     

苯法生产己内酰胺新技术

简述了苯法生产己内酰胺的新工艺技术 ,指出采用环己烷仿生催化氧化或复合金属氧化物催化氧化生产环己酮、环己基过氧化物无碱催化分解成环己醇酮、钛硅分子筛催化环己酮氨肟化生产环己酮肟、烟酸多级重排或分子筛气相重排生产己内酰胺以及进行己内酰胺精制工艺改进是技术发展的方向。     

氯化苯生产中苯流失的分析与对策

分析了氯化苯生产过程中苯的流失问题,并提出了减少苯耗、降低污染的对策。     

负载型杂多酸制备及对苯羟基化反应的活性研究

采用浸渍法和回流吸附法在γ-Al₂O₃、NaX型分子筛、TiO₂、SiO₂和椰壳活性炭载体上制备7种负载型杂多酸催化剂,并对催化苯羟基化制苯酚的反应活性进行研究。结果表明,制备的负载型杂多酸催化剂具有催化活性,且催化活性与负载方式和载体的种类有关,椰壳活性炭是硅钼钒杂多酸最好的载体,负载率达16.3%,苯酚收率7.4%,苯酚选择性97.1%。     

Improvement in hydration resistance of CaO granules by addition of Zr(OH)4 and Al(OH)3

Improving the hydration resistance of CaO aggregates is the key to successful application of lime-based refractories in metallurgical industry. Additive Zr(OH)₄ and Al(OH)₃ were introduced in the preparation of CaO granules using granulation equipment and calcination method in this study. The results showed that the hydration resistance of CaO granules was improved significantly, especially for granules with 0.6 wt.% Zr(OH)₄ and 0.9 wt.% Al(OH)₃, respectively. The shell of CaO granules was relatively dense after calcination and the volume of open pores of CaO granules decreased from 3.56 × 10⁻² to 1.80 × 10⁻² cm³/g when additive was introduced. Zr(OH)₄ and Al(OH)₃ have the opposite effect on the closed porosity of CaO granules, the closed porosity of CaO granules was decreased with Zr(OH)₄ addition, but increased with Al(OH)₃ addition.     

Photocatalytic reactivity and diffusing OH radicals in the reaction medium containing TiO2 particles

The generation of OH radicals on UV-illuminated TiO₂ surface is mainly responsible for the photocatalytic oxidation of pollutants in various contaminated environmental media. Although the reactivity of OH radicals is largely limited within the surface region, the possibility of OH desorption and diffusion into the reaction medium has been often raised. This study provides several examples for the presence of diffusing OH radicals in aqueous solution and polymer matrix containing TiO₂ particles. The photocatalytic degradation rates of (CH₃)₄N⁺ in TiO₂ suspension were comparable between acidic and alkaline conditions, which could not be explained by a simple electrostatic surface charge model. From the present mechanistic study, it is suggested that the photocatalytic oxidation of (CH₃)₄N⁺ at acidic pH mainly proceeds through free OH radicals in the solution bulk, not on the surface of TiO₂. The diffusing OH radicals also played the role of main oxidants in the solid phase. The photolysis of TiO₂-embedded PVC composite films generated cavities around the imbedded TiO₂ particles and the development of cavity diameter continued even after the direct contact between the PVC and TiO₂ was prohibited. This implied that active oxygen species that were photogenerated on TiO₂ surface desorbed and diffused across a few micrometers to react with the polymer matrix.