2143-67-1Relevant articles and documents
Multifunctional Antioxidants with High Activity at Elevated Temperatures Based on Intramolecular Synergism
Yu, Shasha,Liu, Shenggao
supporting information, p. 381 - 385 (2018/01/27)
Multifunctional antioxidants with three active fragments were prepared through a simple two-step synthesis process. These novel compounds exhibited higher efficiency when inhibiting the oxidation of hydrocarbons compared to commercial products at 180 °C.
Revised structure for the diphenylaminyl radical: The importance of theory in the assignment of electronic transitions in Ph2X (X = CH, N) and PhY (Y = CH2, NH, O)
DiLabio, Gino A.,Litwinienko, Grzegorz,Lin, Shuquiong,Pratt, Derek A.,Ingold
, p. 11719 - 11725 (2007/10/03)
Density functional theory indicates that the minimum energy structure of the diphenylaminyl radical, Ph2N, has a "staggered" conformation in which the two phenyl rings are twisted relative to each other by an angle, φ, of 40°. In this conformation, the aromatic rings are oriented so as to maximize interaction with the unpaired electron while minimizing repulsion between the 2- and 2′-hydrogen atoms. This calculated ground state structure of Ph2N differs from that, which has been accepted for the past 15 years, which had the two rings orthogonal (φ = 90°) with one ring conjugating with the nitrogen's lone pair and the other conjugating with the unpaired electron. This structure was based on unexpected differences between the UV-vis absorption spectra of Ph2N and the diphenylmethyl radical. However, our calculations indicate that this orthogonal structure lies 3.5 kcal/mol above the global minimum. Further support for the staggered conformation of Ph2N is provided by the similarities between absorption transition wavelengths determined theoretically and the experimental absorption bands of Ph2N and other diarylaminyl radicals generated by laser flash photolysis. The long wavelength transition of Ph2N, resulting in a structure that can be represented as (Ph2) +N-, is red-shifted as compared to the related transition from Ph2CH to (Ph2)+CH- due to the electronegativity of the N atom. The absorption bands for PhCH2, PhNH, and PhO in the 300-450 nm region are similar in position, which has been taken to indicate that for isoelectronic species the electronic transition energies should be little affected by heteroatom substitution. Our calculations show, however, that these sets of absorption bands arise from different transitions. Therefore, the experimentally similar 300-450 nm absorption bands for these three radicals are fortuitous and do not reflect some common, unifying traits, a fact that further serves to emphasize the importance of theory in the assignment of bands due to electronic transitions.
Bond dissociation energies of the N-H bond and rate constants for the reaction with alkyl, alkoxyl, and peroxyl radicals of phenothiazines and related compounds
Lucarini, Marco,Pedrielli, Pamela,Pedulli, Gian Franco,Valgimigli, Luca,Gigmes, Didier,Tordo, Paul
, p. 11546 - 11553 (2007/10/03)
The results of a detailed thermodynamic and kinetic investigation on the homolytic reactivity of phenothiazine, phenoxazine, and phenoselenazine, of several substituted phenothiazines, and of related tricyclic aromatic amines are reported. All these compo
KINETICS OF THE REACTION OF THE 2,4,6-TRI-TERT-BUTYLPHENOXYL RADICAL WITH AROMATIC AMINES UNDER QUASIEQUILIBRIUM CONDITIONS, AND THE DISSOCIATION ENERGY OF THE N-H BOND IN AROMATIC AMINES
Varlamov, V. T.,Denisov, E. T.
, p. 657 - 662 (2007/10/02)
We have studied the kinetics of the reaction of the 2,4,6-tri-tert butylphenoxyl radical with 11 aromatic amines under quasiequilibrium conditions.The equilibrium constant for each amine was determined from the kinetic results.These values, together with their temperature dependence, were used to calculate the dissociation energy of the N-H bond in the 11 aromatic amines.By using earlier results for the reaction of the aroxyl radical with cumyl hydroperoxide, catalyzed by aromatic amines, we have calculated the rate constants for the reaction of 10 aminyl radicals with cumyl hydroperoxide and of cumylperoxy radicals with 10 aromatic amines.
Picosecond laser photolysis studies on the photoreduction of excited benzophenone by diphenylamine in solutions
Miyasaka,Mataga
, p. 131 - 137 (2007/10/02)
The mechanism of photoreduction of benzophenone (BP) by diphenylamine (DPA) in isooctane as well as acetonitrile and other polar solvents has been investigated by means of picosecond laser photolysis and time-resolved transient absorption spectral measurements. The results of measurements have demonstrated clearly that the hydrogen abstraction and charge transfer (CT) or ion pair (IP) state formation by electron transfer are competing at encounter between triplet benzophenone (3BP*) and DPA both in nonpolar and polar solvent, and the CT or IP state relaxed with respect to the donor acceptor configurations and solvation does not contribute to the ketyl radical formation. It has been concluded that the very short-lived CT state at encounter between 3BP* and DPA plays a crucial role in the hydrogen abstraction reaction, i.e. the mutual orientation of 3BP* and DPA in this very short-lived CT state at encounter will determine the successive process, the formation of the ketyl radical or relaxed CT or IP state.
STUDY OF THE REVERSIBLE REACTION BETWEEN THE DIPHENYLAMINYL RADICAL AND STERICALLY HINDERED PHENOL
Varlamov, V. T.
, p. 1601 - 1606 (2007/10/02)
Two methods of determining the equilibrium constant of the reaction of the diphenylaminyl radical with 2,4,6-tri-tert-butylphenol were proposed; they are based on the high reactivity of aminyl radicals in cleavage of a H atom from phenol and phenoxyl radicals in cleavage of an H atom from an amine.In the first method (generation of aminyl radicals in a system containing phenol and amine), the forward reaction goes into quasiequilibrium, and the maximum concentration of phenoxyl radical formed and the concentrations of the other components calculated from the stoichiometry are used for calculating the equilibrium constant.In the second method (kinetic features of consumption of the phenoxyl radical in the presence of amine and phenol), the reverse reaction goes into quasiequilibrium, and the equilibrium constant is calculated in this case using the initial segments of the kinetic curve of consumption of phenoxyl.Both methods give similar values of the equilibrium constant.
Primary Processes of Stabilizer Action in Radiation-induced Alkane Oxidation
Brede, Ortwin,Hermann, Ralf,Mehnert, Reiner
, p. 2365 - 2380 (2007/10/02)
Results of pulse-radiolytic model experiments on the auto-oxidation of long-chain n-alkanes and auto-oxidation retardation are presented.In pure n-heptadecane and solutions of di-t-butyl-p-cresol or diphenylamine the reaction of alkyl radicals with oxygen and the corresponding competition reactions with the stabilizer prototypes have been characterized by spectroscopic and kinetic data.A reaction mechanism describing the radiation-induced processes within the system long-chain n-alkane-oxygen-stabilizer is discussed.
ESR Studies of Photochemical Reactions of Diphenylamines, Phenothiazines, and Phenoxazines
Lin, Tien-Sung,Retsky, Joel
, p. 2687 - 2689 (2007/10/02)
Detailed photochemical reactions of diphenylamines, phenothiazines, and phenoxazines have been studied by the ESR technique.Our results show nitroxide radicals are the stable products of the photooxidation of both diphenylamines and phenothiazines, while cation radicals are the stable product of the photolyzed phenoxazines in the presence of air.
