4939-72-4Relevant academic research and scientific papers
Kinetic Study of the Phthalimide N-Oxyl Radical in Acetic Acid. Hydrogen Abstraction from Substituted Toluenes, Benzaldehydes, and Benzyl Alcohols
Koshino, Nobuyoshi,Saha, Basudeb,Espenson, James H.
, p. 9364 - 9370 (2007/10/03)
The phthalimide N-oxyl (PINO) radical was generated by the oxidation of N-hydroxyphthalimide (NHPI) with Pb(OAc)4 in acetic acid. The molar absorptivity of PINO. is 1.36 × 103 L mol -1 cm-1 at λmax 382 nm. The PINO radical decomposes slowly with a second-order rate constant of 0.6 ± 0.1 L mol-1 s-1 at 25°C. The reactions of PINO . with substituted toluenes, benzaldehydes, and benzyl alcohols were investigated under an argon atmosphere. The second-order rate constants were correlated by means of a Hammett analysis. The reactions with toluenes and benzyl alcohols have better correlations with σ+ (ρ = -1.3 and -0.41), and the reaction with benzaldehydes correlates better with σ (ρ = -0.91). The kinetic isotope effect was also studied and significantly large values of kH/kD were obtained: 25.0 (p-xylene), 27. 1 (toluene), 27.5 (benzaldehyde), and 16.9 (benzyl alcohol) at 25°C. From the Arrhenius plot for the reactions with p-xylene and p-xylene-d10, the difference of the activation energies, EaD - E aH, was 12.6 ± 0.8 kJ mol-1 and the ratio of preexponential factors, AH/AD, was 0.17 ± 0.05. These findings indicate that quantum mechanical tunneling plays an important role in these reactions.
Primary Processes in the Type I Photocleavage of Dibenzyl Ketones. A Pulsed Laser and Photochemically Induced Dynamic Nuclear Polarization Study
Gould, Ian R.,Baretz, Bruce H.,Turro, Nicholas J.
, p. 925 - 929 (2007/10/02)
The primary homolytic α-cleavage, and subsequent decarbonylation of the intermediate phenacyl radicals, have been studied for the type I photoreaction of a series of dibenzyl ketones, using the techiques of pulsed laser photolysis and photochemically induced dynamic nuclear polarization (photo-CIDNP).Evidence for selective primary cleavage to produce the most stable radical pairs is obtained for unsymmetrical ketones.The absolute rate constants and activation parameters for the decarboxylations are obtained, and the relationships between these and the stabilities of the product radicals is discussed.
