Bimolecular Self-reaction Research Articles

Bimolecular self-reactions of ketyl radicals of acetophenone and diphenylaminyl radicals

The rate constants of self-reactions of ketyl radicals of acetophenone in n-heptane [2 k = (3.2 ± 0.5) × 10 9 M −1 s −1] and diphenylaminyl radicals in toluene [2 k = (3.3 ± 0.5) × 10 7 M −1 s −1] have been determined at 298 K using the flash photolysis technique. The rate constant of ketyl radicals is equal to the calculated diffusion constant and, therefore, this reaction is diffusion-controlled. The aminyl radical recombination rate is independent of the viscosity of the toluene/vaseline oil binary mixture (0.55 ⩽ η ⩽ 12 cP) and this reaction is activation-controlled. Reactivity anisotropy averaging due to the cage effect has been considered for ketyl and some other radicals. On the basis of the analysis it has been proposed that ketyl recombination involves formation of not only pinacol, but also iso-pinacols.

Kinetic applications of electron paramagnetic resonance spectroscopy. 39. Bimolecular self-reactions of some N-alkylcarboxyamidyl, N-alkylsulfonamidyl, and N-alkyl-N-(alkoxycarbonyl)aminyl radicals. Intermolecular hydrogen atom abstraction by N-ethylpropionamidyl radical

Kinetic applications of electron paramagnetic resonance spectroscopy. 39. Bimolecular self-reactions of some N-alkylcarboxyamidyl, N-alkylsulfonamidyl, and N-alkyl-N-(alkoxycarbonyl)aminyl radicals. Intermolecular hydrogen atom abstraction by N-ethylpropionamidyl radical

An electron spin resonance study of sulphuranyl radicals of the type R2S–SX [X = CF3or R′C(O)

Photochemically generated trifluoromethyl- or acyl-thiyl radicals add to dialkyl sulphides to form the sulphuranyl radicals R2S1–S2X [X = CF3 or R′C(O)], the e.s.r. spectra of which have been detected. These adducts appear to be non-planar at the three-co-ordinate sulphur and the unpaired electron is thought to occupy an S–S σ* orbital. The β-hydrogen splittings from the S1-alkyl groups probably arise mainly through a hyperconjugative mechanism of spin transmission and appear to depend upon the spin density (ρ) in the S1-3pσ orbital and the dihedral angle (θ) between the S1CHβ and S2S1C planes according to the approximate equation a(Hβ)= 25.2 ρcos2θ G. The g factors of the sulphuranyl radicals are markedly dependent upon temperature and the nature of R. At low temperatures, the adducts generally decay by a second-order process, presumably bimolecular self-reaction. Different behaviour is observed when R2S = [graphic omitted] or (Et2N)2S and rapid ring-opening or S–N cleavage, respectively, occurs even at low temperatures. Temperature-dependent lineshape effects are evident in the spectra of R2S–SX, and several different processes appear to be responsible for these effects, including efficient spin–rotation relaxation, conformational interconversion, and the bimolecular sulphide exchange reaction R2S + R2S–SX ⇌ R2S–SX + R2S.

ChemInform Abstract: THE KINETICS OF THE BIMOLECULAR SELF‐REACTION OF TERT‐BUTYL RADICALS IN SOLUTION. I. TERMINATION RATES

Chemischer InformationsdienstVolume 10, Issue 4 Preparative Organic Chemistry ChemInform Abstract: THE KINETICS OF THE BIMOLECULAR SELF-REACTION OF TERT-BUTYL RADICALS IN SOLUTION. I. TERMINATION RATES H.-H. SCHUH, H.-H. SCHUHSearch for more papers by this authorH. FISCHER, H. FISCHERSearch for more papers by this author H.-H. SCHUH, H.-H. SCHUHSearch for more papers by this authorH. FISCHER, H. FISCHERSearch for more papers by this author First published: January 23, 1979 https://doi.org/10.1002/chin.197904101Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume10, Issue4January 23, 1979 RelatedInformation

A kinetic study of the reaction of adamantanethione with 2-adamantanethiol

The title reaction is a free radical chain process which yields di(2-adamantyl)disulfide(2). The kinetics of this reaction have been studied in benzene solution at 50 °C using both thermal and photochemical initiation. Thermal initiators which yield resonance stabilized carbon-centered radicals were surprisingly inefficient at starting the reaction. The kinetics indicate that the rate controlling propagation step is hydrogen abstraction from the thiol, AdHSH, by the carbon-centered radical, AdHSSAd•. Rotating sector studies gave a rate constant for this step, k2 = 4 × 104 M−1 s−1. There is some kinetically first order chain termination, but the predominant termination process involves the diffusion-controlled bimolecular self-reactions of AdHSSAd• radicals, 2kt = 1.8 × 1010 M−1 s−1.

Bimolecular self-reaction of peroxy radicals. Oxygen-18 isotope study

Bimolecular self-reaction of peroxy radicals. Oxygen-18 isotope study

The Bimolecular Self-reactions of Secondary Peroxy Radicals. Product Studies

The principal products formed from 1-ethoxyethyl hydroperoxide and 1,2-diphenylethyl hydroperoxide on oxidation with reagents that are presumed to generate the corresponding sec-alkylperoxy radicals (Ce(IV), tert-butoxy, and Ag2O) have been identified. The products formed when the corresponding alkoxy radicals are generated in pairs have also been identified. It is concluded that the Russell (1) concerted cyclic mechanism in which tetroxide decomposed to molecular products is not the exclusive route for the bimolecular self-reaction of sec-alkylperoxy radicals. It is suggested that there is also a second tetroxide decomposition process which yields radical products. The second process may yield "free" alkoxy radicals or it may, perhaps, yield the products of β-scission of the alkoxy radicals in a step concerted with O—O homolysis of the tetroxide. The relative importance of tetroxide decomposition to molecular and to radical products will depend on the structure of the alkyl groups, the temperature and, perhaps, the solvent.