30208-47-0Relevant academic research and scientific papers
Kinetics of the reaction of trifluoromethyl radicals with nitrogen-containing compounds
Pieniazek
, p. 1775 - 1779 (2007/10/03)
A gas-phase kinetic study of hydrogen abstraction from ammonia, methylamine, dimethylamine and trimethylamine has been carried out in a static system by gas chromatography. The photolysis of trifluoromethyl iodide has been used as source of trifluoromethyl radicals. Arrhenius parameters based on Ayscough's value of 1013.16 cm3 mol-1 s-1 for the recombination of trifluoromethyl radicals have been found. The reactions scheme of trifluoromethyl iodide photolysis in the presence of ammonia and amines has been proposed and kinetically interpreted. The trends in chemical reactivity of CF3 are discussed and interpreted by enthalpy effects.
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
Modulation spectroscopy. Kinetics for the self-reactions of some α-aminoalkyl radicals in solution
Marriott, Paul R.,Castelhano, Arlindo L.,Griller, David
, p. 274 - 278 (2007/10/02)
The optical spectra and reaction kinetics of some α-aminoalkyl radicals, RCHN(CH2R)2; R = H, Me, Ph, were measured in solution using the technique of modulation spectroscopy.These radicals undergo diffusion controlled self-reaction with rate constants ca. 109 M-1 s-1.When R=Ph, the absorption spectrum has a well defined maximum at 346 nm; ε = 3390 M-1 cm-1, while the spectra when R = H or Me were less intense (ε346nm ca. 500 M-1 cm-1) and tailed into the visible.These spectra are substantially red-shifted when compared with those of simple alkyl radicals, an effect which is thought to be due to the interaction between the unpaired electron and the lone pair of electrons on nitrogen.
Absolute rate constants for the Reactions of tert-Butoxyl, tert-Butylperoxyl, and Benzophenone Triplet with Amines: The Importance of a Stereoelectronic Effect
Griller, D.,Howard, J. A.,Marriott, P. R.,Scaiano, J. C.
, p. 619 - 623 (2007/10/02)
Absolute rate constants have been determined for the reactions of tert-butoxyl, tert-butylperoxyl, and benzophenone triplet with a variety of amines.All three reagents abstract hydrogen from the carbon α to nitrogen with rate constants which are much greater than those for the corresponding reactions with hydrocarbons and isostructural ethers.This rate enhancement is attributed to polar effects on the transition state and to the stabilization of α-aminoalkyls.These product radicals are stabilized by conjugation between the unpaired electron and the nitrogen lone pair, and, as a result, the hydrogen abstractions show a pronounced stereoelectronic effect with abstraction being most facile when the C-H bond being broken is eclipsed with the axis of the nitrogen lone-pair orbital.
