- Biomass toward fine chemical products: Oxidation of α-pinene over sieves nanostructured modified with vanadium
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Vanadium-containing molecular sieves (V-M(x)) were synthetized and applied as heterogeneous catalysts for the liquid phase oxidation of α-pinene with hydrogen peroxide at 70°C. It has been found that the vanadium content in V-M(x) materials affected the conversion of α-pinene and product distribution. The turnover numbers increased strongly with the decreasing of V content probably caused by a high V dispersion. The major products were verbenone, trans-sobrerol and campholenic aldehyde. The acid-base properties of V-M(x) affected the distribution of products formed via the isomerization of α-pinene oxide over Lewis acid sites to campholenic aldehyde while Br?nsted acid sites brought about the formation of 1,2 pinanediol and trans-sobrerol by hydrolysis and by the opening of oxirane ring. The increase in V content in V-M(x) led to the increase in campholenic aldehyde, 1,2 pinanediol, trans- sobrerol and over oxidation products. Moreover, the effect of several solvents on the reaction oxidation was studied. The results showed that the highest α-pinene conversions are obtained in the following order: acetonitrile > ethanol > isoamyl alcohol > methyl ethyl ketone. Thus, using aprotic solvents, the catalytic activity was increased and the formation of alkyl glycol ethers as by-product was not observed.
- Cánepa, Analía L.,Chanquía, Corina M.,Vaschetti, Virginia M.,Eimer, Griselda A.,Casuscelli, Sandra G.
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- H2O2 based α-pinene oxidation over Ti-MCM-41. A kinetic study
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α-Pinene oxidation with hydrogen peroxide using Ti-MCM-41, prepared by hydrothermal synthesis, with a Ti content of 1.12 wt.% was studied. The major products of reaction observed were: verbenone, verbenol and campholenic aldehyde which are used in the pha
- Cánepa, Analía L.,Herrero, Eduardo R.,Crivello, Mónica E.,Eimer, Griselda A.,Casuscelli, Sandra G.
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experimental part
p. 1 - 7
(2011/10/09)
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- Accelerating ligands for osmium tetraoxide catalyzed racemic dihydroxylation of α-pinene
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Osmium tetraoxide catalyzed racemic cis-dihydroxylation of α-pinene usinf N-oxide as cooxidant and hexamethylenetetraamine as accelerating ligand in tert-butyl alcohol gives excellent yield of α-pinanediol.
- Erdik,Kahya,Daskapan
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- Metal-Catalyzed Oxidations with Pinane Hydroperoxide: A Mechanistic Probe to Distinguish between Oxometal and Peroxometal Pathways
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The relative reactivities of tert-butyl hydroperoxide (TBHP) and pinane hydroperoxide (PHP) in metal (Cr, Mo, Ru, Se, V, and Zr)-catalyzed oxidations were compared. When these oxidations involve rate-limiting oxygen transfer from a peroxometal species to the substrate huge differences between TBHP and PHP were observed, e.g., molybdenum-catalyzed epoxidation of cyclohexene with TBHP gave a 98% yield while PHP gave 0%. When the reaction involves reaction of an oxometal species with the substrate as the rate-limiting step, little or no difference is observed, e.g., the selenium-catalyzed allylic oxidation of β-pinene gave a 96% and 99% yield with TBHP and PHP, respectively. Small but significant differences are observed when reoxidation of the catalyst by the hydroperoxide to the active oxometal species is the rate-limiting step; e.g., the chromium-catalyzed oxidation of carveol gave carvone in 89% and 24% yield with TBHP and PHP, respectively. Hence, the effect of RO2H structure on rate is dependent on the rate-limiting step.
- Lempers,Ripolles i Garcia,Sheldon
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p. 1408 - 1413
(2007/10/03)
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