54050-72-5Relevant academic research and scientific papers
New Kinetic Evidence for Inversional Mechanism in Thermal Geometrical Isomerization about Carbon-Nitrogen Double Bound
Asano, Tsutomu,Okada, Toshio
, p. 691 - 694 (1987)
Kinetic pressure and solvent effects were studied for geometrical isomerization about carbon-nitrogen double bond in N,N-dimethyl-N'--1,4-benzenediamine and 4-imino>-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one.In both of the compounds, the effects clearly demonstrate that the polarity of the reactant decreases slightly during activation, and the results can hardly be reconciled with the previously proposed rotational mechanism.
Solvatochromic behavior of dyes with dimethylamino electron-donor and nitro electron-acceptor groups in their molecular structure
De Melo, Carlos E. A.,Nandi, Leandro G.,Domínguez, Moisés,Rezende, Marcos C.,Machado, Vanderlei G.
, p. 250 - 260 (2015/03/31)
Six dyes with N,N-dimethylaminophenyl and 4-nitrophenyl or 2,4-dinitrophenyl groups in their molecular structures were prepared and characterized. These compounds have different conjugated bridges (C-C, C-N, and N-N) connecting the electron-donor and the electron-acceptor groups. All compounds are solvatochromic, with reverse solvatochromism occurring. The solvatochromic band observed in each spectrum for the dyes is due to a π rarr π? transition, of an intramolecular charge transfer nature, which occurs from the electron-donor N,N-dimethylaminophenyl group to the electron-acceptor group in the molecules, which is reinforced by the structures of the compounds optimized by applying density functional theory, which exhibit high planarity. The reverse solvatochromism was explained considering two resonance structures. The benzenoid form is better stabilized in less polar solvents and characterizes the region displaying positive solvatochromism, while the dipolar form is better stabilized in more polar solvents, in the region of negative solvatochromism. The Catalán multiparametric approach was used to study the contribution of solvent acidity, basicity, dipolarity, and polarizability to the solvatochromism exhibited by the compounds. These compounds are good candidates for the investigation of the polarizability and, to a lesser extent, the dipolarity of the medium, with very little interference from specific interactions of the solvent through hydrogen bonding.
Mechanism of Thermal Z/E Isomerization of Substituted N-Benzylideneanilines. Nature of the Activated Complex with an sp-Hybridized Nitrogen Atom
Asano, Tsutomu,Furuta, Hiroyuki,Hofmann, Hans-Joerg,Cimiraglia, Renzo,Tsuno, Yuho,Fujio, Mizue
, p. 4418 - 4423 (2007/10/02)
In order to study the mechanism of thermal geometrical isomerization involving a sp2-hybridized nitrogen atom, kinetic effects of substituent, solvent, and pressure were studied in substituted N-benzylideneanilines.The effect of the substituent on the aniline moiety was almost independent of the electronic nature of the benzylidene group, and the results could be described satisfactorily by log (k/k0) = ρ0 + r+(?+ - ?0) + r-(?- - ?0)>, except for the 4-(dimethylamino) group.The r- values were more than twice as large as r0, suggesting strongly that the aniline ring is in conjugation not with the carbon-nitrogen ? bond but with the nitrogen lone pair in the transition state.The lower activation enthalpies and fairly large negative activation entropies observed in N-(4-X-benzylidene)-4-nitroanilines also support this view.When a dimethylamino group exists in the 4-position of the aniline ring, the rate constants observed were larger than that expected from the above equation.This deviation suggests the existence of a reaction route where the two phenyl groups become coplanar in the transition state.Ab initio calculations on selected N-phenylformaldimines and N- benzylideneanilines were performed to characterize the actual relation between both reaction possibilities as alternative and parallel routes, respectively.On the basis of the experimental data, the rate constants for the two inversion isomerizations were estimated by assuming parallel reactions for three cases.
Mechanism of Geometrical Isomerization about the Carbon- Nitrogen Double Bond
Asano, Tsutomu,Okada, Toshio,Herkstroeter, William G.
, p. 379 - 383 (2007/10/02)
For pyrazolone azomethines and N-benzylideneanilines, we report kinetic effects of pressure, solvent, and substituent on geometrical isomerization about the carbon-nitrogen double bond.Our results demonstrate the versatility of the inversion mechanism in these two groups of compounds.Invalidated is the rotation mechanism that had been previously predicted for pyrazolone azomethines with electron-donating substituents in the para position of the aromatic ring attached to the imino nitrogen.Contrary to azobenzene, mere push-pull substitution in N- benzylideneanilines is not enough to realize the rotation mechanism even in a relatively polar solvent such as methanol.
