5723-77-3Relevant academic research and scientific papers
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 (1995)
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.
Rates and Mechanisms of the Reactions of Ethanol and Propanol with Fluorine and Chlorine Atoms
Khatoon, T.,Edelbuettel-Einhaus, J.,Hoyermann, K.,Wagner, H. Gg.
, p. 626 - 632 (2007/10/02)
The reactions of C2H5OH (1), C2H5OD (2), C2D5OD (3), 1-C3H7OH (4), 2-C3H7OH (5), 2-C3H7OD (6) with F atoms and the reactions of C2H5OH (7), 1-C3H7OH (8), 1-C3H7OD (9), 2-C3H7OD (10) with Cl atoms have been studied in a discharge flow reactor and a Laval nozzle reactor at room temperature and at pressures of a few mbar.Samples of the reaction mixtures were withdrawn continuously by a molecular beam device and analyzed by a mass spectrometer.The rates of the reactions were measured relative to the standard reactions C2H6 + F (0) and C2H6 + Cl (00) yielding k1/k0 = 1.06 , k2/k0 = 1.25, k3/k0 = 1.20, k4/k0 = 1.26, k5/k0 = 1.06, k6/k0 = 1.20, k7/k00 = 2, k9/k00 = 4.For the reactions of F atoms with alcohols the probability of attack at one of the alkyl H atoms was found to be five times less than at the hydroxyl H atom site.For the reaction of Cl atoms with alcohols no abstraction from the OH group was observed, the abstraction from the alkyl groups follows the thermodynamically favoured route by forming mainly secondary radicals. - Keywords: Chemical Kinetics / Elementary Reactions / Isotope Effects / Mass Spectrometry
