56263-67-3Relevant academic research and scientific papers
Application of a new kinetic method in the investigation of cleavage reactions of haloaromatic radical anions
Enemaerke, Rasmus J.,Christensen, Torben B.,Jensen, Henrik,Daasbjerg, Kim
, p. 1620 - 1630 (2007/10/03)
A simple kinetic method based on competition kinetics is presented for the measurement of cleavage rate constants of radical anions over the range of 107 - 5 × 109 s-1 in aprotic solvents. The standard potential for the formation of the radical anions may be extracted from the kinetic analysis as well. The method employs electrochemical steady-state or optical detection techniques and is an extension of the redox catalysis approach described previously in the literature. The applicability of the method is illustrated through a systematic study of the cleavage reactions for a number of short-lived haloaromatic radical anions. Interestingly, the radical anion of iodobenzene is found to be an intermediate in the homogeneous reduction of iodobenzene, even though recent investigations have shown that the corresponding heterogeneous reduction at an electrode surface proceeds by a concerted electron transfer-bond cleavage process. The nature of the cleavage reactions is discussed in terms of the activation driving force plot of the cleavage rate constants versus the relevant Gibbs energies. While the exergonic cleavage reactions follow a simple decay mechanism taking place at the halogen site, the endergonic processes are best described as intra-molecular electron transfers from the substituent to the carbon-halogen bond. Nevertheless, the overall intrinsic barrier is found to be relatively small (27-39 kJ mol-1) and it is suggested that the endergonic reactions may proceed by a stepwise mechanism, in which a σ* radical anion is formed as an intermediate prior to the formation of the dissociated products, the aryl radical and the halide. The above conclusions were supported by semi-empirical PM3 calculations of structures and charge distributions in the radical anions.
Investigation of the Reactions of Benzonitrile, Ethylbenzene and Cumene with O(3P) in the Gas Phase
Frerichs, H.,Stucken, D.-V.,Tappe, M.,Wagner, H. Gg.
, p. 1 - 10 (2007/10/02)
The rates of the reaction of benzonitrile, ethylbenzene and cumene with atomic oxygen in the ground state 3P)> have been measured in a discharge flow system with mass spectrometric detection.All measurements were performed in an excess of O-atoms in the temperature range 298 K - 873 K.The following Arrhenius expressions for the bimolecular rate constants were obtained: Benzonitrile k(T) = (1.5 +/- 0.4) * 1013 * exp cm3 * mol-1 * s-1, Ethylbenzene: k(T) = (2.2 +/- 0.4) * 1013 * exp * cm3 * mol-1 * s-1, Cumene: k(T) = (2.0 +/- 0.3) * 1013 * exp cm3 * mol-1 * s-1.Kinetics / O-atoms / Aromatic hydrocarbons / Mass spectrometry
Theory and Experimental Illustration of Preparative Electrochemistry Using Redox Catalysis of Electron Transfer Initiated Radical Chain Reactions. Application to the Cross-Coupling between Aryl Halides and Phenoxide Ions
Alam, N.,Amatore, C.,Combellas, C.,Thiebault, A.,Verpeaux, J. N.
, p. 6347 - 6356 (2007/10/02)
A general equation predicting the yield of electron transfer initiated radical chain reaction (SRN1 and related mechanisms) under preparative electrochemical conditions is given for situations where the electron-transfer activation of the chain is performed by means of a redox mediator.Simple tests, allowing for the choice of proper redox mediator, are given, and their origins established and discussed.The validity and application of this simple model is shown and discussed for the case of the SRN1-like reaction involving di-tert-butylphenoxide as a nucleophile, to afford biaryls of interest for their properties in nonlinear optics.
Intramolecular Electron Transfer and Dehalogenation of Anion Radicals. 3. Halobenzonitriles and Cyanobenzyl Halides
Neta, P.,Behar, D.
, p. 103 - 106 (2007/10/02)
One-electron reduction of halobenzonitriles and cyanobenzyl halides produces the anion radicals which then undergo intramolecular electron transfer leading to dehalogenation.Kinetic spectrophotomethric pulse radiolysis allowed the observation of the halobenzonitrile anion radicals and the determination of their dehalogenation rates.The rates varied from 104 to >107 s-1 depending on the halogen and its position relative to cyano group.The production of X- was measured in steady-state radiolysis experiments, and the participation of cyanophenyl radicals as intermediates was also deduced from observation of chain reaction.The anion radicals of cyanobenzyl halides were not observed since they dehalogenate very rapidly.The cyanobenzyl radicals produced by this process were monitored spectrophotometrically.The rates of dehalogenation of the anion radicals studied here are at least 5 orders of magnitude higher than the corresponding values determined previously for analogous nitro derivatives, but the pattern of reactivities is similar in both series of radicals.
Free-Radical Reductions of Arenediazonium Ions in Aqueous Solution. IV. Kinetics of Reactions of para-Substituted Diazonium Ions with Benzyl Alcohol, Isopropyl Alcohol And Methanol
Packer, John E.,Heigway, Christopher J.,Miller, Helen M.,Dobson, Brian C.
, p. 965 - 977 (2007/10/02)
Electron-withdrawing substituents are shown to increase the chain length of free-radical hydrodediazoniation reactions, but the actual reaction step causing the substituent effect depends on the relative rates of propagation and termination reactions.With benzyl alcohol as reducing agent the rate of the slow propagation step is increased, while with isopropyl alcohol the rate of the termination step is decreased.Rate constants for some reactions of radicals with diazonium ions are reported, and the nature of some of these reactions and their implication foran understanding of the homolysis of aromatic diazo compounds are discussed.
