790674-36-1Relevant academic research and scientific papers
Acyl/aroylperoxyl radicals: A comparative study of the reactivity of peroxyl radicals resulting from the α-cleavage of ketones
El-Agamey, Ali,McGarvey, David J.
, p. 1611 - 1617 (2007/10/03)
Employing 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS2-) as a selective radical probe, nanosecond laser flash photolysis (LFP) and competitive kinetic methods have been used to investigate the reactions of acyl/aroylperoxyl radicals derived from the addition of oxygen to the α-cleavage products of various ketones in methanol. The selectivity of ABTS2- for acyl/aroylperoxyl radicals (as opposed to alkylperoxyl radicals), under the experimental conditions used, is supported by the oxygen concentration dependence of the ABTS·- radical ion absorption amplitudes for acyl radicals that undergo decarbonylation on sub-microsecond timescales. The oxygen concentration dependence of the ABTS·- transient absorption reflects the competition between decarbonylation and oxygen addition and therefore this data also provides information on decarbonylation and oxygen addition rates. Further evidence in support of the selectivity of ABTS2- for acyl/aroylperoxyl radicals is the agreement between results obtained from using different ketone precursors for specific acyl/aroylperoxyl radicals. The order of reactivity of the peroxyl radicals towards ABTS2- is found to be aroylperoxyl > acylperoxyl ? alkylperoxyl. The use of ABTS2- as a monitor for acyl/aroylperoxyl radicals has been exploited by using competitive kinetics to obtain rate constants for the reactions of various acyl/aroylperoxyl radicals with vitamin E and trolox.
The Oxidation of Trimethylamine by OH Radicals in Aqueous Solution, as Studied by Pulse Radiolysis, ESR, and Product Analysis. The Reactions of the Alkylamine Radical Cation, the Aminoalkyl Radical, and the Protonated Aminoalkyl Radical
Das, Suresh,Sonntag, Clemens von
, p. 505 - 513 (2007/10/02)
Hydroxyl radical reactions with trimethylamine in aqueous solution lead to the formation of the aminoalkyl radical (A(.)) and its conjugated acid (AH(+.)) as well as to the alkylamine radical cation (CH3)3N(+.) (N(+.)).These radicals are transformed into each other by hydrolytic reactions, e.g. Radicals AH(+.) are more acidic (pKa ca. 3.6) than the radicals N(+.) (pKa ca. 8.0).Consequently, N(+.) predominate over AH(+.) under quasi equilibrium conditions (e.g. in the presence of phosphate buffer) and are the only species observed by ESR in acid solutions.Reacting with the protonated amine, OH radicals abstract hydrogen at nitrogen and at carbon with comparable ease.Reaction of OH radicals with the free amine may initially also generate N(+.), beside H-abstraction at carbon.Radicals A(.) absorb more strongly at 260 nm (ε = 3390 dm3mol-1cm-1) than the radical cation N(+.) (ε = 950 dm3mol-1cm-1).Radical A(.) has reducing properties whereas radicals AH(+.) and N(+.) have oxidizing properties and hence can be monitored with p-nitroacetophenone (the reducing radicals), and Fe(CN)6(4-), N,N'-tetramethyl-p-phenylenediamine and 2,2'-azinobis-(3-ethyl-benzthiazoline-6-sulphonate) (the oxidizing radicals).These radicals mainly (>/=85percent) disproportionate, one of the products being formaldehyde. - Keywords: Radiation Chemistry, Amines, Electron Transfer, Hydrogen Abstraction, Reaction Kinetics
