90889-43-3Relevant academic research and scientific papers
EPR and ENDOR spectroscopic study of the reactions of aromatic azides with gallium trichloride
Bencivenni, Giorgio,Cesari, Riccardo,Nanni, Daniele,El Mkami, Hassane,Walton, John C.
supporting information; experimental part, p. 5097 - 5104 (2010/12/24)
The reactions of gallium trichloride with phenyl and deuterio-phenyl azides, as well as with 4-methoxyphenyl azide and deuterium isotopomers, were examined by product analysis, CW EPR spectroscopy and pulsed ENDOR spectroscopy. The products included the corresponding anilines together with 4-aminodiphenylamine type dimers, and polyanilines. Complex CW EPR spectra of the radical cations of the dimers [ArNHC6H4NH 2]+ and trimers [ArNHC6H4NHC 6H4NH2]+ were obtained. These EPR spectra were analysed with the help of data from the deuterium-substituted analogues as well as the pulse Davies ENDOR spectra. DFT computations of the radical cations provided corroborating evidence and suggested the unpaired electrons were accommodated in extensive π-delocalised orbitals. A mechanism to account for the reductive conversion of aromatic azides to the corresponding anilines and thence to the dimers and trimers is proposed.
The molecularity of the Newman-Kwart rearrangement
Burns, Matthew,Lloyd-Jones, Guy C.,Moseley, Jonathan D.,Renny, Joseph S.
supporting information; experimental part, p. 6347 - 6353 (2010/12/19)
It was recently reported that the venerable Newman-Kwart rearrangement (1→2) proceeds via mixed first- and second-order kinetics. Prior to this, the rearrangement had been considered to proceed exclusively via an intramolecular OAr→SAr migration. A new bimolecular pathway, possibly involving an 8-membered cyclic transition state, was proposed to account for reaction rates that increased disproportionately with substrate concentration under microwave heating conditions. We report a reanalysis of the kinetics and molecularity of the rearrangement of N,N-dimethyl O-(p-nitrophenyl)thiocarbamate 1a in N,N-dimethylacetamide solvent. Using HPLC, isotopic labeling (2H, 18O, 34S), and ESI-ICRMS methods, we show that there is no evidence for a bimolecular pathway en route to 2a, with near-perfect exponential decay in 1a at concentrations ranging from 0.11 to 4.70 M. Instead, it is demonstrated that under the microwave heating conditions, a delayed negative feedback signal to the microwave power balancing loop results in oscillatory reaction overheating. Due to higher tan δ in the solute, the amplitude of this oscillation increases with the concentration of 1a, and this phenomenon best accounts for the kinetic behavior previously misinterpreted as being mixed 'irst- and second-order in nature.
The Mechanism of Nitration of Phenol and 4-Methylphenol by Nitrogen Dioxide in Solution
Coombes, Robert G.,Diggle, Andrew W.,Kempsell, Stewart P.
, p. 6373 - 6376 (2007/10/02)
The quantitative formation of nitrophenols from phenol by reaction with nitrogen dioxide in solution involves stages, the first being the abstraction of a hydrogen atom from the hydroxyl group by NO2. and the second the reaction of the phenoxy radical formed with NO2.The first stage is ratelimiting at high .>.In the case of 4-methylphenol a similar mechanism leads to both 4-methyl-4-nitrocyclohexa-2,5-dien-1-one and 4-methyl-6-nitrocyclohexa-2,4-dien-1-one intermediates and at high .> the apparent rate of the reaction can become the conversion of the latter intermediate into 4-methyl-2-nitrophenol.
Electron Apportionment in Cleavage of Radical Anions. 1. Nitro-Substituted Benzyl Phenyl Ethers
Maslak, Przemyslaw,Guthrie, Robert D.
, p. 2628 - 2636 (2007/10/02)
The radical anions of 4-nitrobenzyl phenyl ethers undergo cleavage at least 10E4 times faster than the radical anions of corresponding 4-nitrophenyl benzyl ethers despite a perceived thermodynamic advantage for the latter set of reactions.It is suggested that this results reflects a kinetic advantage for cleavage reactions which take place with regioconservation of spin density.
The Mechanism of Nitrosation of 4-Nitrophenol with Aqueous Nitrous Acid
Gosney, Alan P.,Page, Michael I.
, p. 1783 - 1787 (2007/10/02)
The nitrous acid catalysed nitration of 4-nitrophenol to give 2,4-dinitrophenol in aqueous solution has been studied under the variety of conditions.At low concentrations of nitrous acid the rate of reaction is dependent upon the concentration of nitrous acid but the rate becomes independent of nitrous acid at high concentrations of nitrous acid when the latter is in excess of 4-nitrophenol concentration.This saturation phenomenon is attributed to the conversion of 4-nitrophenol to its corresponding nitrite ester which then undergoes an acid-catalysed rearrangement to give the accepted normal nitroso ?-complex.Other kinetic parameters, such as salt effects, acidity dependence, and kinetic isotop effects are very similar under the conditions of 'high' and 'low' concentration of nitrous acid.
