N. N. Kabal'nova

Determination of rate constants for quenching singlet oxygen by chemiluminescence technique

Overall rate constants have been found for quenching1O2 generated under thermal decomposition of hydrotrioxides ROOOH, by several unsaturated species at 0°C. CH3CH(OH)OOOHm (CH3)2C(OH)OOOH, CH3C(OC2H5)2OOOH and CH3C(O) CH(OOOH) (CH2)2CH3 were used as ROOOH; unsaturated compounds were 1,3-diphenylisobenzofurane, 2-methylfurane, 2,3,4,5-tetraphenylfurane, furfuroldiacetate, tetramethylethylene, adamantylideneadamantane, exo,-exo-2,3-dioxymethyl-7-adamantylidenenorbornane, exo,-exo-2,3-(21-oxatrimethylene)-7-adamantylidenenorbornane, 1,3-cyclohexadiene, (E,E)-8, 10-dodecadienol, cyclooctatetraene and isoprene.AbstractОпределены брутто константы скорости тушения1O2, генериремого при термическом распаде гидротриоксидов ROOOH рядом ненасыщенных соединений при O°C. В качестве ROOOH использовали CH3CH(OH)OOOH, (CH3)2C(OH)OOOH, CH3C(OC2H5)2OOOH, CH3C(O)CH(OOOH) (CH2)2CH3; ненасышенных соедниений-1,3-дифенилизобензофуран, 2-метилфуран, 2,3,4,5-тетрафенилфуран, фурфуролдиацетат, тетраметилэтилен, адамантилиденадамантан. экзо, экзо-2,3-(21-оксатриметилен)-7-адамантулуденнорборан, 1,3-циклогексадиен, (Э,Э)-8,10-додекадиенол, циклооктатетраен, изопрен.

Reaction of chlorine dioxide with phenol

The kinetics of phenol oxidation with chlorine dioxide in different solvents (2-methylpropan-1-ol, ethanol, 1,4-dioxane, acetone, acetonitrile, ethyl acetate, dichloromethane, heptane, tetrachloromethane, water) was studied by spectrophotometry. In all solvents indicated, the reaction rate is described by an equation of the second order w = k[PhOH]·[ClO2]. The rate constants were measured (at 10—60 °C), and the activation parameters of oxidation were determined. The reaction rate constant depends on the solvent nature. The oxidation products are a mixture of p-benzoquinone, 2-chloro-p-benzoquinone, and diphenoquinone.

The kinetic regularities, products, and mechanism of the thermal decomposition of dimethyldioxirane. The contribution of molecular and radical reaction channels

The products and kinetics of the thermal decomposition of dimethyldioxirane (DMDO) were studied. The reaction proceedsvia three parallel pathways: isomerization to methyl acetate, oxygen atom insertion into the C−H bond of a solvent molecule (acetone), and the solvent-induced homolysis of the O−O bond in the DMDO molecule. The contribution of the latter reaction channel isca. 23% at 56°C. The overall kinetic parameters of DMDO thermolysis in oxygen atmosphere were determined. The free radical-induced DMDO decomposition occurs in an inert atmosphere. The formal kinetics of this reaction was investigated. The mechanism of the DMDO thermolysis is discussed.

Kinetics of thermal decomposition of dimethyldioxirane in oxygen atmosphere

Dimethyldioxirane decomposition in oxygen atmosphere follows a first-order kinetic law. Decomposition rate constant (k, s−1) in acetone in the temperature range from 30 to 50°C has been determined as lgk=(7.1±0.9)−(16.0±1.4)/θ, θ=2.303RT kcal/mol.

Quenching of singlet oxygen by phenols

The rate constants for the quenching of singlet oxygen by sterically hindered phenols were determined. It was observed that the rate constant for the quenching increases with a decrease in the ionization potential of phenols.

Kinetics of formation and thermal decomposition of 1,1-diethoxyethane hydrotrioxide

Conclusions1.The dependence of the yield of hydrotrioxide during the ozonation of 1,1-diethoxy-ethane on temperature and degree of conversion shows that when the process has progressed to a great extent, ozone enters into reaction with the hydrotrioxide.2.The thermal decomposition of 1,1-diethoxyethane hydrotrioxide proceeds mainly by a nonradical mechanism; the fraction of radical decomopsition, measured by the acceptors method, is 1.2%.3.The first discovery was made of the fact that the thermal decomposition of acetal hydrotrioxides is accompanied by chemiluminescence in the IR region.

Oxidation of 1,3-dioxacycloalkanes with dimethyldioxirane

The kinetic regularities of the reactions of dimethyldioxirane with 1,3-dioxane, 2-propyl-, 2-isopropyl-, 2-phenyl-, 2,2-pentamethylene-, 2,2-dimethyl-, and 4-(hydroxymethyl)-2,2-dimethyl-1,3-dioxolanes, as well as with 2-isopropyl-, 2-phenyl-, 2,2,4-trimethyl-, 2-isopropyl-4-methyl-, 4-methyl-, 4-methyl-2-phenyl-, and 5,5-dimethyl-2-phenyl-1,3-dioxanes in acetone were studied by spectrophotometry. The reaction kinetics are described by a second-order equation (first order in dioxirane and first order in dioxacycloalkane). The reaction rate is independent of the concentration of oxygen in the reaction mixture. The activation parameters of the reactions were determined.

Oxidation of alcohols by dimethyldioxirane

The kinetics of oxidation of a series of monoatomic alcohols (methanol, 2-propanol, 2-butanol, 2-methyl-1-propanol, 2-chloroethanol, 1,3-dichloro-2-propanol, benzyl alcohol), hydroxyacetic acid, and 1,3-butandiol (ROH) by dimethyldioxirane (1) was studied. The reaction kinetics obeys the second order equationw=k[ROH][1]. The rate constants were measured in the range of 7–50†C, and the activation parameters were found. To describe the reaction rate constants as a function of the ROH structure, the two-parametric Taft equation was used, which takes into account both the polar and resonance substituent effects. Alcohol oxidation produces the corresponding carbonyl compounds,viz., ketones from secondary alcohols and aldehydes from primary alcohols, in yields of at least 80%. The results were explained by the competition of the molecular (oxenoid) and radical mechanisms. The introduction of electron-withdrawing substituents into the alcohol molecule increases the contribution of the radical channel of the reaction.

Chemiluminescence during ozonation of adamantane on silica gel

Ozonation of adamantane adsorbed on silica gel produces visible chemiluminescence in the wavelength range of 400–650 nm. When the supply of O3 stops, chemiluminescence decays in a first order reaction with the effective rate constant k. Its dependence on the initial amount of adamantane and temperature has been studied.

The formation of nitroxyl radicals in reactions of dimethyldioxirane with 2,2,6,6-tetramethylpiperidine and 2,2,5,5-tetramethyl-3-imidazoline-3-oxide derivatives

The oxidation of secondary and tertiary amines, derivatives of 2,2,6,6-tetramethylpiperidine and 2,2,5,5-tetramethyl-3-imidazoline-3-oxide, by dimethyldioxirane results in the formation of nitroxyl radicals, which induce the decomposition of dimethyldioxirane. Chemiluminescence in the IR and visible regions during the reaction of dimethyldioxirane with 2,2,6,6-tetramethyl-4-hydroxypieeridine-1-oxyl was observed.