S. V. Rykov

Thermolysis of Methanolic Solutions of Acetyl Propionyl Peroxide

Kinetic measurements by 1H NMR spectroscopy and chemically induced dynamic nuclear polarization (CIDNP) effects were used to study thermolysis of solutions of acetyl propionyl peroxide in methanol-d4. It is found that the thermolysis may occur both by radical and by nonradical mechanisms. A scheme of the thermolysis is proposed. Parameters of the Arrhenius equation for the rate constants of the decomposition of the peroxide and the decarboxylation of acyloxyl radicals are obtained.

Photochemical reactions of some mono- and diketo derivatives of adamantane in various solvents

Adamantanes are photoactive in the presence of CCl4 and CDCl3. The mechanism of their photolysis, involving the formation of singlet or triplet excited donor-acceptor complexes has been suggested.

The carbon isotopic effect in photolysis of an aqueous solution of cyclopentanol measured by the NMR method

Using the13C NMR method, the manifestation of the carbon isotopic effect on the products of the photolysis of an aqueous solution of cyclopentanone is investigated. A relative enrichment by the isotope13C of the carbonyl (13%) and α-carbon (6%) atoms of initial cyclopentanone and of the carbonyl atom of pent-4-en-1-ale (11%), as well as the depletion of the carbonyl (15%) and methyl (7%) carbon atoms of valeric acid are revealed. The isotopic effect observed is shown to have a magnetic nature.

Photolysis of a methanolic solution of benzyl acetate in low acoustic fields

The influence of low acoustic fields on the photolysis of benzyl acetate in solution was investigated. A change in the contributions of alternative photolysis mechanisms is caused by destruction of solvate shells.

Photolysis of methanolic solutions of benzyl acetate

Photolysis of solutions of benzyl acetate in CD3OD has been studied. As has been established based on the effects of CIDNP and the yields of products, decomposition of the starting compound occurs from both excited singlet and triplet electronic states. The contributions of homolysis and solvolysis to the overall photochemical process have been measured, and the lifetimes of the acetoxy radicals formed have been evaluated. Toluene-d has been shown to be formed mostly by disproportionation of benzyl radicals with hydroxymethyl radicals derived from the solvent molecules.

Effect of an external magnetic field on photolysis of aqueous solutions of cyclohexanone

The effect of an external magnetic field on the ratio of the yields of the basic products of photolysis of aqueous solutions of cyclohexanone was investigated by high-resolution NMR spectroscopy. It was shown that the magnetic field does not significantly affect the yield of the products of the reaction with a 0.2 M concentration of the starting ketone, the yield of 5-hexenal decreases, and the yield of caproic acid and the rate of photolysis increase below 0.02 M. The observed effects are explained by association of cyclohexan-one with involvement of the HFI mechanism from the theory of “radical pairs.”

Effect of isotope substitution on the magnitude of nonequilibrium nuclear polarization in photolysis of acetone in methanol

Polarization of nuclei in both the products of the reactions and in the CHD2OD proton without polarization in the CH3OH protons is observed in irradiation of a solution of acetone in CD3OD in the presence of CHD2OD and CH3OH. Polarization of the protons of the products is strongly dependent on the temperature of the solution and arises in radical pairs; polarization of the proton of partially deuterated methyl alcohol is due to a mechanism of optical nuclear polarization. It was hypothesized that the isotope effect is due to a difference in proton and electron relaxation and to a difference in the rates of cross-relaxation transitions.

Isotope effect in the gas-phase photolysis of cyclohexanone

An isotope effect was found for the carbonyl and α-carbon atom in the gasphase photolysis of cyclohexanone, which is apparently magnetic in nature. This finding additionally indicates that the chemically induced dynamic nuclear polarization in the gas phase in the photolysis of cyclohexanone arises predominantly in biradicals and not in triplet molecules. The separation of isotopes occurs more efficiently in the photolysis of aqueous solutions of cyclohexanone than in the gas phase.

Nonequilibrium nuclear polarization in the photolysis of aniline solutions

ConclusionsNegative polarization of the protons of aniline and other compounds is observed upon the photoexcitation of aniline solutions. This effect is a consequence of optical nuclear polarization in short-lived donor-acceptor complexes.