The nitro group in aromatic anion radicals-a donor-type substituent

1972 ◽  
Vol 21 (11) ◽  
pp. 2389-2391
Author(s):  
Z. V. Todres ◽  
A. A. Pozdeeva ◽  
V. A. Chernova ◽  
S. I. Zhdanov
Keyword(s):  
Nitro Group ◽  
Donor Type ◽  
Anion Radicals

ESR study of anion radicals produced in cathodic reduction of 2-furfural derivatives

1979 ◽  
Vol 44 (3) ◽  
pp. 762-772 ◽  
Author(s):  
Andrej Staško ◽  
Peter Pelikán ◽  
František Tomanovič ◽  
Viliam Pätoprstý
Keyword(s):  
Nitrogen Atom ◽  
Nitro Group ◽  
Spin Density ◽  
Unpaired Electron ◽  
Indo Method ◽  
Hammett Constants ◽  
Half Wave ◽  
The Individual ◽  
Maximum Spin ◽  
Anion Radicals

Furfural and its derivatives are reduced reversibly to the corresponding anion radicals during polarography in dimethylformamide. These radicals have been studied by ESR, and analysis of their spectra has been carried out. The calculated splitting constants and half-wave potentials (INDO method) agree well with the experiment. The maximum spin density of the unpaired electron has been found for the aldehydic proton of the furfural anion (aH = 1.01 mT), the values for the remaining protons of furane ring being smaller (aH3 = 0.115 mT, aH4 = 0.49 mT, and aH5 = 0.64 mT). Introduction of nitro group in 5 position of furfural results in a marked shift of spin density of the nitrogen atom (aN = 0.533 mT) and decrease of density at the aldehydic proton (aH = 0.334 mT). Chenges of half-wave potentials of the individual furfural derivatives correlate well with changes in the respective Hammett constants of the substituents.

Effects of Ultrasounds on Neat nitrobenzene

2019 ◽  
Vol 70 (8) ◽  
pp. 3085-3088
Author(s):  
Carmen Eugenia Stavarache ◽  
Yasuaki Maeda ◽  
Mircea Vinatoru
Keyword(s):  
Nitro Group ◽  
Radical Cation ◽  
Reaction Mechanisms ◽  
Diphenyl Ether ◽  
Argon Atmosphere ◽  
Phenyl Radical ◽  
Dissolved Gas ◽  
Decomposition Products ◽  
Oxygenated Compounds ◽  
Phenyl Cation

Neat nitrobenzene was continuously irradiated at two ultrasonic frequencies: 40 and 200 kHz, under air and argon atmosphere, respectively. Samples taken at intervals of 1, 5, 10 and 24 h were analyzed by GC-MS and decomposition products were identified. Possible reaction mechanisms are discussed. Presence of air as dissolved gas leads to oxygenated compounds such as 1,4-benzoquinone, 2,4-dinitrophenol, m-dinitrobenzene while argon inhibits the decomposition of nitrobenzene, especially at sonication times under 5 h. Based on the nature of the compounds identified we advanced a mechanism, involving a divergent splitting of unstable radical cation of NB in air and argon respectively. Thus, under air, the phenyl cation formation is preferred leading to 1,4-benzoquinone nitro-biphenyls and dinitrobenzene, while under argon, the phenyl radical formation seems to be favored, leading to phenol and diphenyl ether. The oxygenated compounds detected under argon clearly are a consequence of the nitro group splitting.

Regioselectivity of nucleophilic aromatic photosubstitution in the biphenyl series. Photohydrolysis of some dimethoxynitrobiphenyls

1987 ◽  
Vol 52 (10) ◽  
pp. 2482-2491 ◽  
Author(s):  
Ján Urban ◽  
Petr Kuzmič ◽  
David Šaman ◽  
Milan Souček
Keyword(s):  
Nitro Group ◽  
Steric Hindrance ◽  
The Other ◽  
Quantum Yields ◽  
Hydroxide Anion ◽  
Tert Butanol ◽  
Nitro Derivatives

Anaerobic photolysis of dimethoxynitrobiphenyls IIIa-VIa in aqueous alkaline tert-butanol gave products of nucleophilic photosubstitution of methoxyl by hydroxide anion, while the dimethoxybiphenyls Ia and IIa were found unreactive. Regioselectivity of the reaction was examined in view of a possible “extended meta activation” by the nitro group. The most reactive substrate IIIa gives both C-3 and C-4 substitution products with an unsubstantial preference for the latter, which opposes the “extended meta selectivity” rule. All of the other compounds obey the rule, and 3,4-dimethoxy-3'-nitrobiphenyl (IVa) even displayed absolute selectivity by yielding C-3 substituted compound as the only product. 2,5-Dimethoxy substituted compounds underwent photosubstitution which much lower quantum yields than their 3,4-substituted counterparts, most probably due to some steric hindrance of conjugation. Similarly, 3-nitro-substituted biphenyls exhibited much lower overall reactivity than 4-nitro derivatives.

Photoreaction of N-butyl 3,4-dimethoxy-6-nitrobenzamide with butylamine. A model study for lysine-directed photoaffinity labelling

1987 ◽  
Vol 52 (7) ◽  
pp. 1780-1785 ◽  
Author(s):  
Petr Kuzmič ◽  
Libuše Pavlíčková ◽  
Milan Souček
Keyword(s):  
Nitro Group ◽  
Aromatic Ring ◽  
Ultraviolet Irradiation ◽  
Title Compound ◽  
Reductive Coupling ◽  
Photoaffinity Labelling ◽  
Photolysis Rate ◽  
Model Study ◽  
A Minor

Ultraviolet irradiation of the title compound I in the presence of butylamine gave predominantly products of nucleophilic photosubstitution by the amine, i.e., nitroanilines IIa and IIb. Besides, small amounts of products of hydrolysis (phenol III) and reductive coupling (azoxybenzene IV) were also formed. Comparison of the overall photolysis rate of I with that of 3,4-dimethoxy-1-nitrobenzene (V) indicates a minor loss of reactivity, most probably due to some deviation from coplanarity of the activating nitro group and the aromatic ring.

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