134044-81-8Relevant academic research and scientific papers
Rate constants of elementary steps of the reversible chain reaction of N-phenyl-1,4-benzoquinonemonoimine with 2,5-dichlorohydroquinone
Antonov,Varlamov
, p. 883 - 889 (2007)
The kinetics of reversible chain reactions in quinoneimine-hydroquinone systems has first been studied for the reaction of N-phenyl-1,4- benzoquinonemonoimine with 2,5-dichloro-hydroquinone used as an example. The dependences of the reaction rate on the concentration of the initial reactants, initiator, and each product were studied. The reliable estimates of the rate constants of 11 (of 12) elementary steps of this reaction were obtained from the experimental data using the earlier derived formulas and the method of equal concentrations developed in the present work.
Effect of solvation on the reaction rate constants of the diphenylaminyl radical with phenols and hydroquinones
Antonov,Denisov,Nadtochenko,Varlamov
, p. 91 - 96 (2008/02/13)
The kinetics of the reactions of the diphenylaminyl radical with unhindered phenols and hydroquinones in acetonitrile at 294 K was studied by laser flash photolysis. The rate constants k range from 104 to 106 L mol-1 s-1 and depend on the nature of substituents in phenols and hydroquinones. The k values also depend on the solvent nature and decrease by 6.5 and 50 times, on the average, when decane is replaced by toluene and acetonitrile, respectively. The logk values in decane, toluene, and acetonitrile depend linearly on the dissociation energies D OH of OH bonds in phenols and hydroquinones. Taking into account this dependence and using the experimental k value in acetonitrile, the estimate D OH = 346.6 kJ mol-1 was obtained for 2,5-dichlorohydroquinone. The thermodynamic parameters of formation of H-bonded complexes of phenols and hydroquinones with toluene and acetonitrile were calculated in the framework of the multiplicative approach to thermodynamic description of H-bonding. The rate constants k (free) of the reactions of the diphenylaminyl radical with free phenols and hydroquinones in toluene and acetonitrile were estimated. Comparison of the k (free) values with each other and experimental k values in decane suggests that the changes in k upon solvent replacement is mainly caused by the formation of H-complexes of phenols and hydroquinones with the solvent. Springer Science+Business Media, Inc. 2007.
Photoreduction of p-Benzoquinones: Effects of Alcohols and Amines on the Intermediates and Reactivities in Solution
Goerner, Helmut
, p. 440 - 448 (2007/10/03)
The photochemistry of 1,4-benzoquinone (BQ) and alkyl-, Cl- and related derivatives, e.g. methyl-, 2,6-dimethyl-, chloro-, 2,5-dichloro-1,4-benzoquinone, duroquinone and chloranil, was studied in nonaqueous solvents by UV-vis spectroscopy using nanosecond laser pulses at 308 nm. The reactivity of the triplet state (3Q*) of the quinones with 2-propanol in the absence of water is largest for BQ and depends mainly on the quinone structure, whereas the rate constant of electron transfer from amines, such as triethylamine (TEA) or 1,4-diazabicyclo[2.2.2]octane, is close to the diffusion-controlled limit for BQ and most derivatives. Photoinduced charge separation after electron transfer from amines to 3Q* and the subsequent charge recombination or neutralization are supported by time-resolved conductivity measurements. The half-life of the decay kinetics of the semiquinone radical (.QH/Q.-) depends significantly on the donor and the medium. The photoconversion into the hydroquinones was measured under various conditions, the quantum yield, λirr = 254 nm, increases with increasing 2-propanol and TEA concentrations. The effects of quenching of 3Q*, the .QH/Q.- radicals and the photoconversion are outlined. The mechanisms of photoreduction of quinones in acetonitrile by 2-propanol are compared with those by TEA in benzene and acetonitrile, and the specific properties of substitution are discussed.
