Kinetics of the oxidation of aliphatic ketones by thallic salts in sulfuric acid medium

: - - 1–3 .

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With increasing partial pressure of molecules in atomic-molecular mixtures, the yield and intensity of radical-recombination luminescence of inorganic luminophors increase by 1–3 orders of magnitude.

     

Sorption of aliphatic ketones from aqueous solutions by starch cryotextures

Capillary gas chromatography was applied to study the sorption of aliphatic ketones (C₆—C₁₁), including metamers, from aqueous solutions by corn starch cryotextures. The amount of ketones sorbed by cryotextures depends linearly on their concentrations in the initial sol. Equations describing the concentration dependence of sorption were proposed. The shape of sorption isotherms reflects the strength of sorption. The binding constants and the number of binding sites were determined for weakly sorbed ketones. The length of alkyl substituent and the position of the functional group are the crucial factors governing the sorption of ketones under conditions of excess binding sites. It was found that the degree of sorption increases with an increase in the carbon chain length from 6 to 9 carbon atoms. The presence of cooperation of binding sites for ketone sorption by cryotextures was demonstrated. The major part of ketones is sorbed irreversibly. This fact points to the formation of supramolecular complexes. Ketones with lower molecular masses are better sorbed by cryotextures than by native starch grains.     

Mechanism of oxidation of some aliphatic ketones by N-bromosuccinimide in acidic media

Kinetics of the oxidation of methyl n-propyl ketone and methyl isobutyl ketone by N-bromosuccinimide (NBS) have been studied in perchloric acid media in presence of mercuric acetate. A zero order dependence to N-bromosuccinimide and a first order dependence to both ketones and hydrogen ion concentrations have been observed. Sodium perchlorate, mercuric acetate and succinimide additions have negligible effect while methanol addition has a positive effect on the reaction rate. A solvent isotope effect (k₀D₂O/K₀H₂O = 2.3-2.7 and 2.4-2.8 for MeCOn.pr and MeCoi-Bu, respectively) has been observed at 35°. Kinetic investigations have revealed that the order of reactivity is methyl n-propyl ketone > methyl isobutyl ketone. Various thermodynamic parameters have been computed and corresponding 1,2-diketones were found to be the products. A suitable mechanism in conformity with the above observations has been proposed.     

Kinetics and mechanism of the oxidation of some aliphatic ketones by n-bromoacetamide in acidic media

Kinetics of the oxidation of methyl ethyl ketone (MEK) and diethyl ketone (DEK) by N-bromoacetamide (NBA) have been studied in perchloric acid media in the presence of mercuric acetate. A zero order dependence to NBA and a first-order dependence to both ketones and H⁺ have been observed. Acetamide, mercuric acetate and sodium perchlorate additions have negligible effect while addition of acetic acid has a positive effect on the reaction rate. A solvent isotope effect (K₀D₂O/k₀H₂O = 2.–.4 and 2.2-2.5 for MEK and DEK, respectively) has been observed at 40°. Kinetic investigations have revealed that the order of reactivity is MEK > DEK. The rates were determined at four different temperatures and the activation parameters were evaluated. The main product of the oxidation is the corresponding 1,2-diketone. A suitable mechanism consistent with the above observations has been proposed.     

Kinetics of oxidation of some aliphatic ketones by ditelluratocuprate(III) in alkaline medium

The kinetics of oxidation of some ketones by ditelluratocuprate(III) were followed spectrophotometrically by estimating the disappearence of potassium ditelluratocuprate(III). The reaction follows first order kinetics in both substrates and oxidant. A correlation is found between the order of reactivity and partial rates of enolization of these ketones. By assuming that the mechanism of oxidation involves the enol form of the ketone in a slow step, the observed order of reactivity of these ketones is explained.

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(III) , (III). , , . . , , .

     

Steric effects in the hypervalent iodine oxidation of ketones

Oxidation of 3-cholestanone (1) with C₆H₅I(OAc)₂ or o-OIC₆H₄COOH or C₆H₅IO₂ in KOH/MeOH yields 2 α-carbomethoxy-A-norcholestane (2). This result is interpreted on mechanistic grounds and compared with the course of the reaction with other sterically hindered ketones such as friedelin, 3-keto, 12-keto, 17-keto steroids, and 2,2,6,6-tetramethyl-4-piperidone.     

Direct remote oxidation of aliphatic ketones to δ- andδ-diketones

Aliphatic ketones are converted into °- and °-diketones in one-pot oxidation reaction on treatment with Na₂S₂O₈ in presence of Fe(II)ions.     

Photopolymerization of methyl methacrylate sensitized by aliphatic ketones

The polymerization of methyl methacrylate photosensitized by several alkyl ketones has been investigated. It was found that alkyl ketones can induce the free radical polymerization of the monomer with an efficiency that increases when the triplet lifetime decreases. For ketones of similar triplet lifetime those decomposing predominantly by a type I photocleavage show greater initiation efficiencies than those that react by a type II mechanism. The results obtained show that quenching of the excited ketones by the monomer does not induce polymerization. For ketones bearing γ-hydrogens the initiation is due to the 1,4-biradical produced by intramolecular hydrogen abstraction.     

Temperature dependent near-UV molar absorptivities of aliphatic aldehydes and ketones in aqueous solution

Temperature dependent molar absorptivities are reported for acetone, 2-butanone, 2-pentanone, 3-pentanone, acetaldehyde, propionaldehyde, and n-butyraldehyde in aqueous solution. Molar absorptivities are given at eight temperatures in the range 6.5–69.5°C for wavelengths greater than 200 nm, a spectral resolution of 2.0 nm, and a spacing of 2.5 nm. For both ketones and aldehydes a shift to shorter wavelengths of approximately 10 nm is observed in the aqueous phase absorption spectrum relative to that found in the gas phase. For the ketones, there is an increase in the total intensity of the spectrum of approximately 5% over the range of temperatures studied. For the aldehydes a much larger change in the intensity of the absorption spectrum is observed, due to the temperature dependence of the hydration reaction RCHO + H₂O ⇄ RCH(OH)₂; K_hyd = [RCH(OH)₂/[RCHO]. The change in the spectral intensity with temperature is used to determine thermodynamic parameters for the hydration reaction, giving the following results (at 25°C): acetaldehyde, K_hyd = 1.13 ± 0.06, ΔH = −19.7±0.6kJ/mol, ΔS= −65.0±2.5J/mol-K; propionaldehyde, K_hyd=1.02±0.06, ΔH=-20.8±0.8kJ/mol, ΔS=-69.6±3.1J/mol-K; n-butyraldehyde, K_hyd=0.50±0.05, ΔH=-27.0±2.2kJ/mol, ΔS= −96.5± 8.2 J/mol-K. The implications of these results for aqueous phase atmospheric chemistry are discussed.     

Reactions of aliphatic ketones on zeolites

Reactions of some ketones (acetone, methyl ethyl ketone and diethyl ketone) on the H-form of ZSM-5, ZSM-11, mordenite and erionite have been studied in an integral reactor. At a reaction temperature of 300 or 350°C acetone is selectively transformed on all these zeolites into isobutene, while with higher ketones substantial amounts of aromatics are formed.

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(, ) - ZSM-5, ZSM-11 . , 300 350°C , .

     

Reactions of acyloxiranes with aliphatic ketones

Acyloxiranes react with aliphatic ketones in the presence of boron trifluoride etherate to give the corresponding 4-acyl-1,3-dioxolanes. The corresponding 4,5s-dimethyl-4r-acetyl-1,3-dioxolanes are formed in this case from 2,3t-dimethyl-2r-acetyloxirane, whereas a mixture of cis- and trans-1,3-dioxolanes is formed from trans-2-acetyl-3-phenyloxirane and acetone. The reaction of acyloxiranes with unsymmetrical ketones gives a mixture of the cis- and trans-1,3-dioxolanes with respect to the substituents attached to C-2 relative to the acetyl group, whereas the isomer ratio in this case depends on the effective volumes of the substituents attached to C-2.     

Formation of hydrotrioxides in the low-temperature ozonization of aliphatic ketones

Conclusions The ozonization of 2-butanone and 2-hexanone at from –70°C to –60°C leads to the corresponding hydrotrioxides, which undergo first-order thermal decomposition accompanied by intense chemiluminescence in the visible and IR regions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1660–1662, July, 1985.     

Low-energy mass spectra of some aliphatic ketones

The charge exchange mass spectra of a selection of C₅-C₇ ketones have been measured using [CS₂]⁺˙, [COS]⁺˙ and [N₂O]_+. as reagent ions. The low energy charge exchange with [CS₂]⁺˙ or [COS]⁺˙ provides simple primary ion mass spectra, which readily permit structure elucidation in contrast to metastable ion spectra. In several cases, isomer distinction is easier from the charge exchange mass spectra than from the electron impact mass spectra. The energy transfer from [N₂O]⁺˙ is sufficiently high for complex spectra resembling electron impact mass spectra to be obtained.     

Electroreductive crossed pinacol coupling of aromatic ketones with aliphatic ketones and aldehydes

The intermolecular crossed pinacol coupling of aromatic ketones with aliphatic aldehydes and ketones was effected by electroreduction in the presence of chlorotrimethylsilane. The best result was obtained using a Pb cathode in Bu₄NPF₆/THF. The electroreduction of aromatic 1,4-, 1,5-, and 1,6-diketones under the same conditions gave four-, five-, and six-membered 1,2-diols with trans-stereoselectivity, while the reduction of these diketones with TiCl₄-Zn produced the cis-isomers of the same intramolecular crossed pinacol coupling products predominantly.     

Kinetics of catalytic oxidation of aliphatic alcohols in aqueous alkaline solutions of copper phenanthroline complexes

The effect of Cu(II), phenanthroline, alcohol, NaOH and O₂ concentrations on the oxidation rates of alcohols in aqueous alkaline solutions has been studied and a reaction mechanism is proposed.

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Cu(II), , , NaOH, O₂ - . .

     

Enantioselective organocatalytic reductive amination of aliphatic ketones by benzothiazoline as hydrogen donor

The chiral phosphoric acid-catalyzed enantioselective reductive amination of aliphatic ketones with aromatic amines was successfully achieved by the use of benzothiazoline as the hydrogen donor. Corresponding chiral aliphatic amines were obtained with excellent enantioselectivities.