Sample records for benzhydrol

  1. Correlation analysis of reactivity in the oxidation of some para- substituted benzhydrols by triethylammonium chlorochromate in non-aqueous media

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    S. Sheik Mansoor


    Full Text Available Triethylammonium chlorochromate (TriEACC oxidation of some para-substituted benzhydrols (BH in dimethylsulfoxide (DMSO leads to the formation of corresponding benzophenones. The reaction was run under pseudo-first-order conditions. The reaction is catalyzed by hydrogen ions. The hydrogen ion dependence has the form: kobs = a + b[H+]. Various thermodynamic parameters for the oxidation have been reported and discussed along with the validity of isokinetic relationship. Oxidation of benzhydrol was studied in 18 different organic solvents. The rate data showing satisfactory correlation with Kamlet–Taft solvatochromic parameters (α, β and π∗ suggests that the specific solute–solvent interactions play a major role in governing the reactivity, and the observed solvent effects have been explained on the basis of solute–solvent complexation. A suitable mechanism of oxidation has been proposed.

  2. Synthesis and characterization of Nb2O5 supported Pd(II)@SBA15: Catalytic activity towards oxidation of benzhydrol and Rhodamine-B (United States)

    Ramanjaneya Reddy, G.; Chennakesavulu, K.


    The mesoporous silica (SBA15) supported niobium pentoxide(Nb2O5) along with the palladium(II) nanocomposite catalysts was synthesised. The nanocomposites (PdSBA and NbPdSBA) impregnation and stability were studied by several spectroscopic, thermal analysis, sorption and microscopic techniques (FTIR, DRS/UV-Vis, XRD, XPS, BET - nitrogen adsorption isotherms, TGA, SEM and TEM). The catalytic activity of the nanocomposites was studied in liquid phase oxidation of benzhydrol/H2O2 and photo degradation of the Rhodamine-B (RhB) under UV light irradiation. The catalytic activity of the nanocomposite NbPdSBA was shows higher catalytic activity in the benzhydrol oxidation and RhB degradation. The oxidation ability of the nanocomposites was determined by the spectrophotometrically. Thus a reusable catalyst shows comparable activity with fresh catalyst without loss of it's activity.

  3. Photo catalytic reduction of benzophenone on TiO{sub 2}: Effect of preparation method and reaction conditions

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    Albiter E, E.; Valenzuela Z, M. A.; Alfaro H, S.; Flores V, S. O.; Rios B, O.; Gonzalez A, V. J.; Cordova R, I., E-mail: mavalenz@ipn.m [IPN, Escuela Superior de Ingenieria Quimica e Industrias Extractivas, Laboratorio de Catalisis y Materiales, Zacatenco, 07738 Mexico D. F. (Mexico)


    The photo catalytic reduction of benzophenone was studied focussing on improving the yield to benzhydrol. TiO{sub 2} was synthesized by means of a hydrothermal technique. TiO{sub 2} (Degussa TiO{sub 2}-P25) was used as a reference. Catalysts were characterized by X-ray diffraction and nitrogen physisorption. The photo catalytic reduction was carried out in a batch reactor at 25 C under nitrogen atmosphere, acetonitrile as solvent and isopropanol as electron donor. A 200 W Xe-Hg lamp ({lambda}= 360 nm) was employed as irradiation source. The chemical composition of the reaction system was determined by HPLC. Structural and textural properties of the synthesized TiO{sub 2} depended on the type of acid used during sol formation step. Using HCl, a higher specific surface area and narrower pore size distribution of TiO{sub 2} was obtained in comparison with acetic acid. As expected, the photochemical reduction of benzophenone yielded benzopinacol as main product, whereas, benzhydrol is only produced in presence of TiO{sub 2} (i.e. photo catalytic route). In general, the hydrothermally synthesized catalysts were less active and with a lower yield to benzhydrol. The optimal reaction conditions to highest values of benzhydrol yield (70-80%) were found at 2 g/L (catalyst loading) and 0.5 m M of initial concentration of benzophenone, using commercial TiO{sub 2}-P25. (Author)

  4. SO3H-functionalized organic-inorganic ionic liquids based on polyoxometalates characterization and their application in Csbnd C coupling reaction (United States)

    Rafiee, Ezzat; Mirnezami, Fakhrosadat; Kahrizi, Masoud


    Different ionic liquids (ILs) with SO3H as functional group were achieved by combining SO3H-functionalized organic cations and polyoxometalates (POM). The obtained salts were characterized and their catalytic activities investigated in Csbnd C coupling between benzhydrol and aromatic compounds at neat conditions, including the effect of organic cations, influence of POMs, optimization of reaction conditions, and reusability of the catalyst. Furthermore, Recovery, reusability and activity of ILs as heterogeneous catalysts were studied at least four times.


    Institute of Scientific and Technical Information of China (English)

    Bao-jun Qu


    The radical intermediates, the crosslink microstructures, and the reaction mechanism of benzophenone (BP)-photoinitiated crosslinking of low-density polyethylene (LDPE) and model compounds (MD) have been reviewed in detail.The spin-trapping electron spin resonance (ESR) spectra obtained from the LDPE/BP systems with spin-trap agents showthat two kinds of polymer radical intermediates are mainly formed: tertiary carbon and secondary carbon radicals. The spin-trapping ESR studies of MD/BP systems give further evidence that photocrosslinking reactions of PE predominantly takeplace at sites of tertiary carbon, secondary carbon, and especially allylic carbon when available. The high resolution 13C-NMR spectra obtained from LDPE and MD systems show that the crosslink microstructures have H- and Y-type links andthat their concentrations are of the same order. The fluorescence, ESR, 13C and 1H-NMR spectra from the PE and MDsystems demonstrate that the main photoreduction product of BP (PPB) is benzpinacol formed by the recombination of twodiphenylhydroxymethyl (K*) radical intermediates. Two new PPB products: an isomer of benzpinacol with quinoid structure,1-phenylhydroxymethylene-4-diphenylhydroxymethyl-2,5-cyclohexadiene and three kinds of a-alkyl-benzhydrols have beendetected and identified. These results provide new experimental evidence for elucidating the reaction mechanism in the BP-photoinitiated crosslinking of polyethylene.

  6. Determination of ultraviolet filters in water samples by vortex-assisted dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry. (United States)

    Zhang, Yufeng; Lee, Hian Kee


    For the first time, a simple solvent microextraction method termed vortex-assisted liquid-liquid microextraction (VADLLME) coupled with gas chromatography-mass spectrometry (GC-MS) has been developed and used for the analysis of six benzophenone ultraviolet (UV) filters (i.e. benzhydrol, 2,4-dihydroxybenzophenone, benzophenone, 2-hydroxy-4-methoxybenzophenone, ethylhexyl salicylate and homosalate) in water samples. The most favorable extraction variables in the VADLLME process were determined. In the extraction procedure, 40 μL of tetrachloroethene as extraction solvent were directly injected into a 15-mL centrifuge tube containing 10 mL of aqueous sample, adjusted to pH 4 for VADLLME. After VADLLME, the extract was evaporated under a gentle nitrogen gas stream and then reconstituted with N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA), thus allowing the target analytes to be converted into their trimethylsilyl derivatives to optimize the GC-MS analysis. No centrifugation and disperser solvent were required in this microextraction procedure. Significantly, short extraction time and high extraction efficiency were achieved. This method opens up a potentially new horizon for on-site dispersive liquid-liquid microextraction. Under the optimum conditions, the proposed method provided good enrichment factors up to 310, with relative standard deviations ranging from 6.1 to 12.9%. The limits of quantification were in the range of 20-100 ng/L, depending on the analytes. The linearities were between 0.05 and 10 μg/L and 0.1 and 10 μg/L for different UV filters. Finally, the proposed method was successfully applied to the determination of UV filters from spiked genuine water samples and acceptable recoveries over the range of 71.0-120.0% were obtained.