- KINETICS AND MECHANISM OF OXIDATION OF SOME KETONES BY N-BROMOACETAMIDE
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The kinetics of oxidation of n-butyl methyl ketone (n-BMK) and i-butyl methyl ketone (i-BMK) by N-bromoacetamide (NBA) is studied in perchloric acid media in the presence of mercuric acetate.The main product of the oxidation is the corresponding 1,2-dicarbonyl compound.The reaction order with respect to NBA is zero while with respect to ketone and H+ it is unity.Mercuric acetate, acetamide and sodium perchlorate have negligible effect on the reaction rate, while the dielectric effect is negative.A solvent isotope effect (k0(D2O)/k0(H2O) = 1.80-2.05 and 1.70-2.06 for n-BMK and i-BMK, respectively ) at 35 deg C is observed.On the basis of the available evidence a suitable mechanism consistent with the experimental results is proposed in which it is suggested that the mechanistic route for NBA oxidation is through the enol form of the ketone in an acidic medium.
- Singh, Bharat,Shrivastav, Rohit
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- Selective alkene oxidation with H2O2 and a heterogenized Mn catalyst: Epoxidation and a new entry to vicinal cis-diols
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Covalent anchoring of 1,4-dimethyl-1,4,7-triazacyclononane on silica gel is the first step in the preparation of a heterogenized Mn catalyst. When H2O2 is used as the oxidant, this material can catalyze the vicinal cis- dihydroxylation of disubstituted olefins, as shown schematically here. Both enantiomers of the product are obtained.
- De Vos, Dirk E.,De Wildeman, Stefaan,Sels, Bert F.,Grobet, Piet J.,Jacobs, Pierre A.
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p. 980 - 983
(2007/10/03)
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- The male pheromone of the old house borer Hylotrupes banjulus (L.) (Coleoptera: Cerambycidae): Identification and female response
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We report here the identification of the long-range, male-produced sex pheromone of the Old house borer Hylotrupes bajulus. Chemical analysis of hexane extracts obtained by surface extraction from dissected prothoracic glands and from headspace samples of the two sexes, revealed male-specific compounds: (3R)-3-hydroxy-2-hexanone, 2-hydroxy-3-hexanone, the diastereomeric diols (2R, 3R)-2,3-hexanediol and (2S, 3R)-2,3-hexanediol, 2,3-hexanedione, as well as 1-butanol. In wind tunnel bioassays we tested the influence of these male-specific compounds from the prothoracal glands on the behaviour of unmated and mated females. Specific behavioural sequences of the tested females (activity, running behaviour, searching, cleaning, flying, extension of ovipositor) were recorded. Unmated females were attracted by male beetles, headspace extracts of males, synthetic blends of the major pheromone compounds as well as by the components (3R)-3-hydroxy-2-hexanone, and the diastereomeric diols. Hexane, female beetles and 2,3-hexanedione did not attract unmated females. The reactions of mated females to male beetles and headspace samples did not differ significantly from those of the controls. The results of the bioassays show that the two-stage premating behaviour is initiated by emission of a long-range sex pheromone from the male prothoracal glands, which functions as an activator, attractant, and possibly aphrodisiac for unmated females.
- Fettkother,Dettner,Schroder,Meyer,Francke,Noldt
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p. 270 - 277
(2007/10/02)
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- Cobalt(II)-Catalyzed Reaction of Aldehydes with Acetic Anhydride under an Oxygen Atmosphere: Scope and Mechanism
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The reaction of aldehydes with acetic anhydride in the presence of catalytic cobalt(II) chloride under an oxygen atmosphere at ambient temperature is dependent upon the reaction medium.Aliphatic aldehydes react in acetonitrile to give 1,2-diones whereas the aromatic aldehydes are acylated to yield the corresponding acylals.On the other hand, carboxylic acids are obtained from aliphatic and aromatic aldehydes by conducting the reaction in dichloroethane or benzene.Cobalt(II) chloride in acetonitrile catalyzes the conversion of aliphatic aldehydes to the correspondinganhydrides in the absence of acetic anhydride whereas aromatic aldehydes remain largely unaffected under these conditions.A preliminary mechanistic study in three different solvents (i.e. acetonitrile, dichloroethane, and DMF) has revealed that in acetonitrile and in the presence of acetic anhydride, aliphatic aldehydes behave differently than aromatic aldehydes.Some trapping experiments using methyl acrylate and stilbene have been conducted to demonstrate the occurence of an acyl cobalt and peroxyacyl cobalt intermediate during these reactions.
- Bhatia, Beena,Punniyamurthy, T.,Iqbal, Javed
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p. 5518 - 5523
(2007/10/02)
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- Cobalt(II) Chloride Catalysed Coupling of Acetic Anhydride with Aldehydes. A Novel Synthesis of Asymmetrical 1,2-Diones
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Cobalt(II) chloride in acetonitrile efficiently catalyses the coupling of acetic anhydride with various aldehydes to the corresponding 1,2-diones in very high yields.
- Ahmad, Saeed,Iqbal, Javed
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p. 692 - 693
(2007/10/02)
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