[en] The yields of radicals in the γ-radiolysis of liquid acetic and propionic acids were measured using spin traps MN and BNB. These conclusions are compared with the yields of the end products CH₄, C₂H₆ and CO₂, inhibited by addition of spin traps. The reduction of the yields of the trapped radicals is due to charge transfer from dimeric radical cations of the acids to the traps. A correlation was obtained between the yields of trapped radicals and the ability of the traps to capture a positive charge. The ionic-molecular reaction of proton transfer within the dimer, followed by decarboxylation of the acyloxy radical, is the predominant process; the yields of alkyl radicals formed are equal to the yields of R·CO radicals, within the limits of error. 10 refs., 4 figs., 1 tab

[en] The formation and reactions of radical cations of dimethylformamide and tetramethylurea in Freon solutions which were γ-irradiated at 77 K, i.e., the ion-molecule reactions occurring upon irradiation, as well as upon the phase transition in the matrix, and intramolecular hydrogen transfer, have been investigated by ESR. Fragmentation with the formation of Me₂N predominates in the pure amides in the liquid phase, as was demonstrated with the aid of spin traps

[en] Solutions of the spin traps and acids were evacuated to 5 x 10^-5 torr and irradiated with gamma rays at 20⁰ or -196⁰C. The most suitable spin traps appear to be 2,4,6-tri-tert-butylnitrosobenzene (BNB) and tert-butylmethylenenitrone (MN). The EPR spectra of these substances in acetic and propionic acid were recorded. The principal products are the alkyl and acyl radicals, while CH₂COOH and CH₃CHOOH are formed as secondary products. Formation of the adducts with BNB and MN are described, along with their temperature dependence. Hyperfine structure parameters of the adducts were calculated, and the results seem to agree with literature values. 12 references, 3 figures, 1 table

[en] The dependence of hydrogen yields on c-phenyl-tert-butylnitrone (PBN) concentration in the radiolysis of methanol and methanol water mixtures was studied. The change in the kinetics of H₂ formation when PBN is added to these mixtures is related to the nature of the radical adducts trapped. 15 references, 1 figure

[en] In CFCl₃ matrices the cation-radicals of methyl and ethyl formates, formed in γ-irradiated solutions, at 77 K efficiently undergo intramolecular H atom transfer to form the secondary cation-radicals HC(OH)OCH₂CH₂ and DC(OH)OCD₂CH₂. This process does not occur in the deuteroformate cation-radical DCOOCH₂CD₃/sup +./, which is observed in the ESR spectra in different conformations, depending on the temperature. Ion-molecule reactions involving cation-radicals are indicated

[en] Quantum-chemical (MNDO-UHF) calculations of electronic, spin and energy characteristics of radical cations (RC) of ethanal, propanal, butanal, and pentanal and their distonic isomers were performed. The calculations both with 'frozen' (vertical ionization) and completely optimize geometry (adiabatic approximation) were made. It was been shown that the most positive charge and spin population are localized at O atoms and adjacent C atom as well as at aldehyde protons. The C-H bonds corresponding to those protons as well as neighboring C-O and C-C bonds are considerable weaker (longer) in radical cations as compared to their neutral precursors. That is why such reaction centers are apt to deprotonation with the formation of acyl radical as well as to α- and β-splitting (scission) which are well-known from aldehydes mass-spectra. Our calculations shown that distonic RC (products of intramolecular H-atom transfer) are more stable as compare to their classical isomers: e.g. the difference in energy ΔE = -0.95 eV, -1.2 eV, and -1.5 eV for tree distonic isomers of butanal RC as compare to classical isomer, ΔE -1.2 eV for distonic RC of ethanal. The results of calculations are effectively correlated with ESR data obtained in freonic solutions, X- and gamma-irradiated at 77 K and in liquid aldehydes, X-irradiated by using 2,4,6-tri-tert-burylnitrosobenzene (BNB) and t-BuNO (NtB) as a spin traps. (author)

[en] The effect of 2-propanol on radical yields in γ-irradiated acetone has been studied by spin-trapping method. 2-propanol has proved to suppress the CH₂COCH₂ and CH₃ yields and to increase the (CH₃)₂COH yield. The results are explained by the ion-molecular reaction between acetone primary cation and 2-propanol. (author)

[en] In solutions of acetone and methyl ethyl ketone in CFCl₃ (0.1-22%) γ-irradiated at 77 K, monomeric and dimeric cation-radicals of the ketones, as well as RCHCOMe radicals, are stabilized with yields dependent on the ketone concentration in the CFCl₃. On exposure to light the dimeric cation-radicals are converted to RCHCOMe while the monomers disappear without forming radicals. It is shown that different types of ion-molecule reactions occur in the solid phase in which the monomeric and dimeric cation-radicals participate

[en] This paper investigates the ESR spectra of solutions of acetone and methyl ethyl ketone (MEK) in CFCl₃ (Freon II) that were gamma-irradiated at -196 C. The ketones used in this work were chemically pure. An analysis of the spectra indicated that a reduction of the acetone concentration brings about a decrease in the relative yield of acetonyl radicals and an increase (symbatic) in the yield of cation radicals Me₂CO⁺, the total concentration of radicals being constant over a broad range of acetone concentrations. A reduction of the MEK concentration from 0.5 to 0.08 M lowers the yield of the CH₃COCHCH₃ radicals, with an equivalent increase in the yield of cation radicals

[en] Electronic processes in γ-irradiated diethyl ether glass are studied by EPR. In pure diethyl ether the radiation chemical yield for trapped electrons and CH₃CHOCH₂CH₃ radicals is 1.2 and 2.7, respectively. Trapped electrons leave their traps upon light irradiation (λ ≥ 370 nm) and are captured by the radicals. In diethyl ether glass with 3 x 10^-4-0.2 M C-phenyl-N-terbutylnitrone (PBN) added, the resultant yield of paramagnetic particles is practically independent of the PBN concentration and is equal to the total yield in neat diethyl ether (3.9). For small PBN concentrations a dark transfer of trapped electrons from the physical traps to acceptor occurs (probably via tunneling mechanism) with the formation of PBN^- anion-radicals