2348-46-1Relevant academic research and scientific papers
Absolute Rate Constant for the Reaction of O(3P) with Ethanol
Grotheer, Horst-Hemming,Nesbitt, Fred L.,Klemm, R. Bruce
, p. 2512 - 2518 (1986)
The rate constant for the reaction of atomic oxygen with ethanol was measured directly by two experimental techniques: flash photolysis-resonance fluorescence (FP-RF, 297-886 K) and discharge flow-resonance fluorescence (DF-RF, 298-706 K).Kinetic complications in the DF-RF experiments from a fast secondary reaction and heterogeneous effects were overcome by operating at very low initial O-atom concentrations combined with the addition of excess O2.Under these conditions results obtained in the DF-RF experiments were in very close agreement with those from the FP-RF work, which was not perturbed by any apparent complication.The combined results show slight non-Arrhenius behavior and the data were accordingly fit to a three-parameter expression, 298-886 K, k1(T) = 9.88 * 10-19T2.46 exp(-932/T), in units of cm3 molecule-1 s-1, with an error limit of about +/- 15percent over the given temperature range.In addition, initial variation experiments were carried out at 298 K in the DF-RF apparatus to investigate the mechanism of this reaction, and model calculations for an assumed mechanism were performed.Finally, the branching ratios for the three possible H-abstraction channels are discussed in light of the non-Arrhanius behavior displayed in the present rate data.
The reactivity of ketyl and alkyl radicals in reactions with carbonyl compounds
Denisov
, p. 2110 - 2116 (2007/10/03)
A parabolic model of bimolecular radical reactions was used for analysis of the hydrogen transfer reactions of ketyl radicals: >C+OH + R1COR2 → >C=O + R1R2C+OH. The parameters describing the reactivity of the reagents were calculated from the experimental data. The parameters that characterize the reactions of ketyl and alkyl radicals as hydrogen donors with olefins and with carbonyl compounds were obtained: >C+OH + R1CH=CH2 → >C=O + R1C+ HCH3; >R1CH=CH2 + R2C+HCH2R3 → R2C+HCH3 + R2CH=CHR3. These parameters were used to calculate the activation energies of these transformations. The kinetic parameters of reactions of hydrogen abstraction by free radicals and molecules (aldehydes, ketones, and quinones) from the C-H and O-H bonds were compared.
Determination of Absolute Rate Constants for the Reversible Hydrogen-atom Transfer between Thiyl Radicals and Alcohols or Ethers
Schoeneich, Christian,Asmus, Klaus-Dieter,Bonifacic, Marija
, p. 1923 - 1930 (2007/10/02)
Absolute rate constants have been determined for the reversible hydrogen-transfer process R. + RSH ->/. by pulse radiolysis, mainly through direct observation of the RS. radical formation kinetics in water-RH (1:1, v/v) mixtures.The thiols investigated were penicillamine and glutathione; the RH hydrogen donors were methanol, ethanol, propan-1-ol, propan-2-ol, ethylene glycol, tetrahydrofuran and 1,4-dioxane with the abstracted hydrogen being located α to the hydroxy or alkoxy function.Rate constants for the forward reaction of the above equilibrium (in radiation biology referred to as 'repair' reaction) were typically of the order of 1E7-1E8 dm3 mol-1 s-1 while hydrogen abstraction from RH by thiyl radicals (reverse process) occurred with rate constants of the order of 1E3-1E4 dm3 mol-1 s-1.This yields equilibrium constants of the order of 1E4.Based on these data, standard reduction potentials could be evaluated for the R'R''C.OH/H(1+)//R'R''CHOH, R'R''CO/H(1+)//R'R''C.(OH) and R'R''CO//R'R''C.O(1-) couples from methanol, ethanol and propan-2-ol.Effective hydrogen-atom abstraction by RS. required activation by neighbouring groups of the C-H bond to be cleaved in RH.No such process was observed for the RS. reaction with -CH3 groups, e.g. in 2-methylpropan-2-ol.Several halogenated hydrocarbons, including some anaesthetics (e.g. halothane) and Fe(CN)6(3-) have been tested with respect to their ability to disturb the (CH3)2C.OH + RSH ->/. equilibrium through an irreversible electron-transfer reaction with the reducing α-hydroxyl radical, thereby drawing the equilibrium to the left-hand side.The respective efficiencies are found to be related to the electronegativities of the electron acceptors.The results are briefly discussed in terms of their biological relevance.
