67958-03-6Relevant 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.
SN1-type mechanism for the carbon-carbon bond cleavage of tetrakis(4-methylphenyl)ethanone cation radical. A laser flash photolysis study
Akaba, Ryoichi,Kamata, Masaki,Sakuragi, Hirochika,Tokumaru, Katsumi
, p. 8105 - 8108 (2007/10/02)
On the basis of measurements of rate constants for carbon-carbon bond cleavage of tetrakis(4-methylphenyl)ethanone cation radicals generated by pulsed laser excitation with sensitizers in solution, an SN1-type mechanism for the bond cleavage is proposed.
Kinetics for Reaction of the Nitrate Radical (NO3.) with aldehydes in Acetone in Acetonitrile
Ito, Osamu,Akiho, Seiji,Iino, Masashi
, p. 4079 - 4083 (2007/10/02)
The rate constants for the reactions of NO3. with RCHO (R: H, CH3, C2H5, CH(CH3)2, and C(CH3)3 and XC6H4CHO (X: NO2, CN, Cl, H, and OCH3) have been measured by following the decay of the transient absorption band of NO3. generated by photolysis of K2 in acetonitrile.Representative rate constants (in unit of M-1 s-1) at 20 deg C in acetonitrile are 2.3E7 for CH3CHO and 2.4E7 for PhCHO.The hydrogen-atom abstraction reaction of NO3. from the aldehydic C-H was confirmed by the similarity of the above two rate constants and by the higher reactivites than those of acetone and benzene.The rate constants for HCHO and CH3CHO in aqueous solution are smaller than the corresponding values in acetonitrile, because of the hydration.For aliphatic aldehydes, the methyl substitution on the vicinal carbon to aldehydic carbon slightly increase the reactivity of the aldehydic C-H with NO3..A large negative Hammett reaction constant (ρ=-1.3) for aryl aldehydes indicates the high electrophilicity of NO3..The polar substituents stronly affect the orientation factors rather than the activation energies, which were obtained by the Arrhenius plots.The rate constants in acetonitrile, however, are ca. 30 times larger than the corresponding ones reported in the gas phase: a polar mediun affects the distribution of an unpaired electron and the polar nature of the reaction.
