Nitrobenzene radical anion

Kalyanaraman, V.; Rao, C. N. R.; George, M. V.

doi:10.1016/s0040-4039(01)88838-9

Cited by 11 publications

(4 citation statements)

References 6 publications

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“…The single broad (absorption) envelopes shown in Figure 6 are generally similar to that described by Kemula and Sioda 23 and do not show any additional component beyond 500 nm. This observation agrees with George's conclusion 25 that the Tsubomura spectra 24 must have been affected by impurities. Furthermore, the NB -• spectra reported by Suga and Aoyagui 27 were also not free of contaminants.…”

Section: Resultssupporting

confidence: 92%

“…Thus, Kemula and Sioda 23 found a pair of UV bands at λmax = 435 and 465 nm (both with ε ≅ 1500 M -1 cm -1 ) for nitrobenzenide anion prepared polarographically in DMF, and similar spectral results were reported by Tsubomura and co-workers 24 when nitrobenzene was reduced with potassium in DME but with an additional band at 560 nm. By contrast, George and coworkers 25 identified only a single absorption at 440 nm as being characteristic of nitrobenzenide anion, and the other spectral bands were ascribed to byproducts of further chemical reduction (among which were the anion-radical and dianion of nitrosobenzene, azobenzene, azoxybenzene, and anilinoazoxybenzene, etc). Although the shape of the band was not discussed, its bathochromic shift with cation size in the order Li + (440 nm), Na + (444 nm), and K + (470 nm) indicated to them a mixture with "... the ratio of intimate and solvent-separated species ..." varying with solvent and countercation.…”

Section: Uv−vis Studies Of Nitrobenzenide Ion Pairsmentioning

confidence: 92%

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Crystallographic Distinction between “Contact” and “Separated” Ion Pairs: Structural Effects on Electronic/ESR Spectra of Alkali-Metal Nitrobenzenides

Davlieva

Lindeman

et al. 2004

J. Am. Chem. Soc.

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The classic nitrobenzene anion-radical (NB(-*) or nitrobenzenide) is isolated for the first time as pure crystalline alkali-metal salts. The deliberate use of the supporting ligands 18-crown-6 and [2.2.2]cryptand allows the selective formation of contact ion pairs designated as (crown)M(+)NB(-*), where M(+) = K(+), Rb(+), and Cs(+), as well as the separated ion pair K(cryptand)(+)NB(-*)-both series of which are structurally characterized by precise low-temperature X-ray crystallography, ESR analysis, and UV-vis spectroscopy. The unusually delocalized structure of NB(-*) in the separated ion pair follows from the drastically shortened N-C bond and marked quinonoidal distortion of the benzenoid ring to signify complete (95%) electronic conjugation with the nitro substituent. On the other hand, the formation of contact ion pairs results in the substantial decrease of electronic conjugation in inverse order with cation size (K(+) > Rb(+)) owing to increased localization of negative charge from partial (NO(2)) bonding to the alkali-metal cation. Such a loss in electronic conjugation (or reverse charge transfer) may be counterintuitive, but it is in agreement with the distribution of odd-electron spin electron density from the ESR data and with the hypsochromic shift of the characteristic absorption band in the electronic spectra. Most importantly, this crystallographic study underscores the importance of ion-pair structure on the intrinsic property (and thus reactivity) of the component ions-as focused here on the nitrobenzenide anion.

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Section: Resultssupporting

confidence: 92%

Section: Uv−vis Studies Of Nitrobenzenide Ion Pairsmentioning

confidence: 92%

Crystallographic Distinction between “Contact” and “Separated” Ion Pairs: Structural Effects on Electronic/ESR Spectra of Alkali-Metal Nitrobenzenides

Davlieva

Lindeman

et al. 2004

J. Am. Chem. Soc.

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“…Examination of Table 1 reveals that the starting nitrones are characterized by an absorption maximum around 298-353 nm, whereas the corresponding radical anions showed a red shifted absomtion maximum around 320-450 nm: the corresponding dianions, however, showed an absorption maximum around 280-295 nm. These observations are in tune with the spectral data reported for the radical anions and dianions derived from azobenzene and nitroaromatics through their reaction with lithium in THF (17)(18)(19)). An interesting observation was that the radical anions 2a-d, 27a,b, 35, and 50 and the dianions 3a-d, 28a,b, and 36 were quenched by oxygen, as evidenced by the disappearance of their absorption bands, on bubbling oxygen gas through their solutions in acetonitrile.…”

Section: Cyclic Voltammetric Studiessupporting

confidence: 86%

Electron transfer reactions. Reaction of nitrones with potassium

Ashok¹,

Scaria²,

Kamat³

et al. 1987

Can. J. Chem.

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KONDA ASHOK, PALLIKKAPARAMBIL M. SCARIA, PRASHANT V. KAMAT, and MANAPURATHU V. GEORGE. Can. J. Chem. 65, (1987).Treatment of nitrones ( l a -d , 26a,b, 34, 49) with potassium in tetrahydrofuran (THF) gives rise to radical anion (2a-d, 27a,b, 35, 50) and dianion intermediates (3a-d, 28a,b, 36) through electron transfer reactions. These intermediates undergo further transformations to give a variety of products. Thus, the aldehydonitrones ( l a -d ) give the corresponding aldehydes (1Oa-c), carboxylic acids (25a-c), and azobenzenes (19a,d), whereas the ketonitrones (26a,b) give deoxygenation products (31a,b). The nitrone 34 gave a mixture of products consisting of benzoic acid (25a), dibenzyl(48), the dimeric product 38, and tetraphenylpyrazine (46), whereas 49 did not give any isolable product. Cyclic voltammetric studies have been employed to measure the reduction potentials for both one-electron and two-electron transfer processes, leading to the radical anions and dianions respectively. These intermediates have been characterized through their electronic spectra and they were quenched by oxygen. Pulse radiolysis of the nitrones [Traduit par la revue]

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“…The NB's radical anion is more stable and does not suffers splitting. This radical anion is similar with those of NB reduction with metals [23]. However, this radical anion could react with other reactive species ultrasonically generated, leading therefore to the NB sonodegradation products, like nitrozobenzene, di-nitrobenzene and nitrobiphenyls.…”

Section: Influence Of Dissolved Gassupporting

confidence: 58%

Effects of Ultrasounds on Neat nitrobenzene

Stavarache¹,

Maeda²,

Vînătoru³

2019

Rev. Chim.

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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.

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Nitrobenzene radical anion

Cited by 11 publications

References 6 publications

Crystallographic Distinction between “Contact” and “Separated” Ion Pairs: Structural Effects on Electronic/ESR Spectra of Alkali-Metal Nitrobenzenides

Crystallographic Distinction between “Contact” and “Separated” Ion Pairs: Structural Effects on Electronic/ESR Spectra of Alkali-Metal Nitrobenzenides

Electron transfer reactions. Reaction of nitrones with potassium

Effects of Ultrasounds on Neat nitrobenzene

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