Selective oxidation of alkenes catalysed by ruthenium(II) complexes containing coordinated perchlorate
TL;DR: In this paper, the selective homogeneous oxidation of cyclohexene with TBHP and H2O2 as oxidizing agents was investigated. And the results showed that TBHP was more effective than H 2 O 2 as an oxidizing agent.
Abstract: Ruthenium(II) perchlorate complexes, [Ru(dppm)3(ClO4)]ClO4 1, [Ru(dppe)3(ClO4)]ClO4 2, and [Ru(dpae)3(ClO4)]ClO4 3, catalyse the selective homogeneous oxidation of alkenes with TBHP and H2O2 as oxidizing agents. Oxidation of cyclohexene with TBHP gave 2-cyclohexene-1-ol, 2-cyclohexenone and 1-(tert-butylperoxy)-2-cyclohexene. The homogeneous liquid phase oxidation of cyclohexene with TBHP shows appreciable solvent effect. Styrene on oxidation with TBHP gave benzaldehyde as the major product and styrene oxide as the minor product. Oxidation with H2O2 is radical-initiated and gives low conversion to products. TBHP and H2O2 are compared for their oxidizing ability and TBHP is more effective than H2O2 as an oxidizing agent. Linear and long chain alkenes are not efficiently oxidized. Cyclooctene and trans-stilbene are oxidized to the corresponding epoxides.
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TL;DR: In this article, a simple physical-vapor-infiltration (PVI) method was applied to prepare highly ordered Fe-containing mesoporous silica SBA-15.
Abstract: A simple physical-vapor-infiltration (PVI) method was applied to prepare highly ordered Fe-containing mesoporous silica SBA-15. The loading amount of Fe in SBA-15 was very high (up to 24 mol%) and can be tuned by using different PVI time. The liquid phase selective oxidation of styrene with H 2 O 2 has been used to characterize their catalytic properties, the major product is benzaldehyde and the minor is styrene oxide. Independent of the Fe contents and the heat treatment temperature, the selectivity for benzaldehyde in the reaction at a mild temperature of 50 °C are all above 91%. At elevated temperature of 70 °C, the conversion rate of styrene increases beyond 36% and more significantly the selectivity for benzaldehyde can reach as high as 99%. Comparatively, another two different schemes (simple wet impregnation and incorporation using silane coupling agent) have been also applied to synthesize Fe-containing SBA-15 samples. Under the same condition, the styrene conversion on these two samples are both very low with minor product of phenylacetaldehyde and other styrene oxides.
41 citations
TL;DR: In this paper, the coupling of microwave energy with solvent-free phase-transfer catalysis was studied for the oxidation of cyclohexene and styrene, and parallel oxidations were successfully employed by using a special microwave set-up.
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TL;DR: In this paper, an environmentally benign oxidation of alcohols and alkenes over transition metal substituted phosphomolybdates with molecular oxygen as an oxidant and TBHP as an initiator was carried out.
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TL;DR: In this paper, the authors used a robust biosorption system consisting of a bacterial biofilm, Arthrobacter viscosus, supported on zeolite NaY.
Abstract: The goal of this study is the preparation of new heterogeneous catalytic materials to be used in oxidation reactions under mild conditions through the valuation of heavy metals in wastewater. The samples used in the immobilization of chromium complexes were prepared from a dichromate solution of 100 mgCr L � 1 . The zeolite CrNaY was prepared from a robust biosorption system consisting of a bacterial biofilm, Arthrobacter viscosus, supported on zeolite NaY. The biofilm performs the reduction of Cr(VI) to Cr(III) and this cation is retained in the zeolite by ion exchange. The immobilization of chromium complexes with heterocyclic ligands in the supercages of Y zeolite was performed by the in situ synthesis with three different ligands, 3-methoxy-6-chloropyridazine (A), 3-piperidino-6-chloropyridazine (B) and 1-(2pyridylazo)-2-naphthol (C). A sample loaded with Cr from a liquid solution with the same initial concentration was prepared as a reference through the traditional direct ion-exchange method and coordinated with ligand (A). The resulting catalysts were fully characterized by different techniques (FTIR, XRD, TGA, SEM, Raman, cyclic voltammetric studies and chemical analysis) and the results confirmed that the Cr complexes were immobilized in supercages of NaY. Catalytic studies were performed in liquid phase for the cyclohexene oxidation, at 40 8C, using tert-butyl hydroperoxide (TBHP) as the oxidizing agent. All the prepared catalysts exhibited catalytic activity for the oxidation reaction.
29 citations
TL;DR: In this article, Co2+ exchanged supported 12-tungstophosphoric acid was synthesized and characterized for the oxidation of alkenes such as styrene, cyclohexene, and cis-cyclooctene under mild conditions.
Abstract: Co2+ exchanged supported 12-tungstophosphoric acid was synthesized and characterized. Its catalytic activity was evaluated for the oxidation of alkenes such as styrene, cyclohexene and cis-cyclooctene under mild conditions. The superiority of the catalyst lies efficiently in catalyzing the non-solvent liquid phase oxidation of alkenes, especially oxidation of cyclohexene with 98% conversion and 57% selectivity for cyclohexene oxide, with molecular oxygen at 1 atm pressure. The active intermediate, responsible for the oxidation of alkenes, was also isolated and characterized by ESR. Its catalytic activity was evaluated for the oxidation of styrene under optimized conditions. Based on the above study a probable reaction mechanism was also proposed.
28 citations
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TL;DR: In this article, the authors compared the selectivities of epichlorohydrin and allyl chloride with several organic hydroperoxides, and found that the lower selectivities were due to their facile heterolytic decomposition under the reaction conditions.
83 citations
TL;DR: A series of [RuVILO2] complexes (H2L =Para-substituted tetraphenylporphyrins) have been synthesized and characterized, and the kinetics and mechanism of oxidation of the C-H bond and alkenes investigated as mentioned in this paper.
Abstract: A. Series of [RuVILO2] complexes (H2L =Para-substituted tetraphenylporphyrins) have been synthesised and characterized, and the kinetics and mechanism of oxidation of the C–H bond and alkenes investigated. The complexes were selective towards tertiary C–H bonds in saturated alkanes but were almost inactive towards secondary C–H bonds. However, they were reactive towards aromatic hydrocarbons and the second-order rate constants (k2) for the oxidation of ethylbenzene and cumene by [Ru(tpp)O2](tpp = 5, 10, 15, 20-tetraphenylporphyrinate) were 2.21 × 10–4 and 3.16 × 10–4dm3 mol–1 s–1 respectively. A kinetic isotope effect (KH/KD) of 11.7 was found for the allylic oxidation of cyclohexene by [Ru(tpp)O2]. The major organic products of the oxidation of alkenes in CH2Cl2–MeOH mixtures were epoxides and [Ru(tpp)O2] gave a monomeric product formulated as [RuIV(tpp)O]·EtOH. or [RuIV(tpp)(OH)2·]EtOH. Similar reactions with [RuVI(oep)O2](oep = 2,3,7,8,12,13,17,18-octaethylporphyrinate) gave [{RuVI(oep)(OH)}2O] in non-co-ordinating solvents. The observed rate law for alkene oxidation was rate =K2[RuVI][alkene]. There exists an almost linerar free-energy relationship between log k2 and E½(one-electron oxidation potentials of alkenes) with slope =–1.1 V–1 for the [Ru(tpp)O2] system. Activation parameters have been determined for the oxidation of styrene, norbornene and cyclooctene by [RuVILO2]. Non-linear and U-shaped Hammett plots were observed for the oxidation of substituted styrenes. The mechanism of alkene oxidation is proposed to involve a continum of transition states, the structures of which may change and be stabilized by defferent substituents.
52 citations
TL;DR: Quaternary ammonium salts assist the extraction of both hydrogen peroxide and metal salts, e.g. ruthenium or palladium chloride from the aqueous to the non-aqueous component of a two-phase system.
Abstract: Quaternary ammonium salts assist the extraction of both hydrogen peroxide and metal salts, e.g. ruthenium or palladium chloride from the aqueous to the non-aqueous component of a two-phase system; the system has been used for the oxidation of styrene.
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27 citations
TL;DR: In this article, the various industrial processes for the manufacture of a variety of bulk and fine chemicals are reviewed and compared, focusing on the new development trends that constitute the driving force for industrial research on catalytic oxidation.
Abstract: Summary The various industrial processes for the manufacture of a variety of bulk and fine chemicals are reviewed and compared. Emphasis is placed on a discussion of the new development trends that constitute the driving force for industrial research on catalytic oxidation. For example, the rationale underlying changes in feedstocks for certain products and the implications arising from the trend towards low-salt technologies are discussed. Interesting recent developments having practical implications, such as the use of phase transfer catalysis and the application of redox zeolites and redox pillared clays as unique solid catalysts for liquid phase oxidations are reviewed.
24 citations