Nitrobenzene spectra

In the M. trichosporium OB3b system, a third intermediate, T, with kmax at 325 nm (e = 6000 M-1cm 1) was observed in the presence of the substrate nitrobenzene (70). This species was assigned as the product, 4-nitrophenol, bound to the dinuclear iron site, and its absorption was attributed primarily to the 4-nitrophenol moiety. No analogous intermediate was found with the M. capsulatus (Bath) system in the presence of nitrobenzene. For both systems, addition of methane accelerated the rate of disappearance of the optical spectrum of Q (k > 0.065 s-1) without appreciatively affecting its formation rate constant (51, 70). In the absence of substrate, Q decayed slowly (k 0.065 s-1). This decay may be accompanied by oxidation of a protein side chain. 

MgO, respectively. Photolysis by an incandescent lamp is necessary to produce the radical on MgO, and the light significantly alters, both in amplitude and shape, the spectrum of the species on silica-alumina. Both spectra are interpreted in terms of very anisotropic hyperfine interactions. This is consistent with work on radical anions such as nitrobenzene on MgO (90) however, it is a bit surprising in light of the motional averaging found for most cations on silica-alumina. 

The PE spectrum of nitrobenzene (Figure 19) has been investigated repeat-edly21,139-142,144. 

Other compounds containing a nitrobenzene unit like substituted benzamides145, azobenzenes146, iV - ben zy I i den can i I i n cs147 and donor-acceptor cyclophanes148 have been investigated by PES. The PE spectrum of l-methyl-3-nitro-2-phenylindole (68) has been measured130. 

The use of ammonia for the protonation of nitroarenes leads frequently to formation of aduct ions, e.g. [M + NH4]+, but not to the protonated species (MH+)112,113. The ammonia chemical ionization spectrum of nitrobenzene shows, in addition to a series of adduct ions, a dominant signal corresponding to the anilinium ion (m/z 94)112114115. Evidence for the isomerization of the [M + NR ]"1" adduct followed by successive loss of NO and OH or NH3 to give ions corresponding to the substitution products, e.g. the anilinium ion, has been given115 see Scheme 41. 

Electron transfer [Eq. (1)] would occur at a rate near the diffusion limit if it were exothermic. However, a close estimate of the energetics including solvation effects has not been made yet. Recent support of the intermediacy of a charge transfer complex such as [Ph—NOf, CP] comes from the observation of a transient (Amax f 440 nm, t =2.7 0.5 ms) upon flashing (80 J, 40 ps pulse) a degassed solution (50% 2-propanol in water, 4 X 10 4 M in nitrobenzene, 6 moles 1 HCl) 15). The absorption spectrum of the transient is in satisfactory agreement with that of Ph—NO2H, which in turn arises from rapid protonation of Ph—NOf under the reaction conditions ... 

The anion-radicals from aromatic nitro compounds preserve the second-order axis of symmetry. The analysis of superfine structure of the ESR spectrum of the nitrobenzene anion-radical reveals equivalency of the ortho and meta protons (Ludwig et al. 1964, Levy and Myers 1965). With the anion-radical of nitrosobenzene, the situation is quite different. This was evidenced from the ESR data (Levy and Myers 1965, Geels et al. 1965). Following electron transfer, the bent nitroso group fixes in the plane of the benzene ring to a certain extent. This produces five different types of protons, since both meta and ortho protons become nonequivalent. The nonequivalence of the ortho and meta protons has also been established for the anion-radicals of acetophenone (Dehl and Fraenkel 1963) and 5-methylthiobenzoate (Debacher et al. 1982 Scheme 6.17). 

The IR spectrum of 1,2,4-thiadiazolidine-3,5-dione indicates that the dithione structure (13) predominates. However, the dithione can be readily dialkylated on sulfur and treatment with 1-chloro-4-nitrobenzene in aqueous sodium hydroxide yields (150) (Scheme 33) <89EUP330020>. 

Nitrobenzene. The 250 nm primary or 1La band of nitrobenzene has been explained by Nagakura34 in terms of an intramolecular charge transfer spectrum. He suggests that interaction between the highest occupied orbital of the donor part of the molecule (the phenyl ring) and lowest unoccupied... 

Cyanopentakis(benzyl isonitrile)iron(II) bromide, which represents a new class of iron isonitrile complexes, was investigated in some detail. This complex is diamagnetic and dissociates in nitrobenzene into two univalent-univalent ions as indicated by cryoscopic and conductivity measurements. It exhibits two peaks in the triple bond region of the infrared spectrum one at 2200 cm.—1 assigned to the isonitrile groups and another at 2092 cm.-1 assigned to the cyano group. The structure proof of cyanopentakis (benzyl isonitrile) iron (II) bromide is ... 

Figure 3.17 IR spectrum of nitrobenzene (liquid film, NaCl plates)...

Figure 15.1 Electronic absorption spectrum of nitrobenzene in aqueous solution at 0.1 mM. (a) Absorbance A as a function of wavelength. (b) Log as a function of wavelength.

Give the number of lines in the ESR spectrum of the anion radical of each of the following molecules. (Assume all lines are resolved.) (a) Naphthalene (b) anthracene (c) pentacene (d) azulene (e) o-xylene (f) w-xylene (g) p-xylene (h) nitrobenzene (i) />-fluoronitrobenzene. 

The well-known photorearrangement of urtAo-nitrobenzaldehyde to orfAo-nitrosobenzoic acid458 may well involve hydrogen abstraction as the initial photoprocess. Nitrobenzene is photoreduced in reactive solvents to iV-phenylhydroxylamine,459 and the intermolecular hydrogen abstraction apparently proceeds from the triplet state, since, when perfluoronaphthalene is present in the sample, the ESR spectrum of the PhN02H radical is replaced by the typical triplet ESR spectrum of the naphthalene.460... 

Figure 2. FT-IR spectra of (a) nitrocyclohexane (575K), (b) nitrobenzene (575K), (c) acetic acid (575K), and (d) nitrosobenzene (475K) adsorbed at a.-Mn 04. (Spectrum (d) is found to be assignable to surface azoxybenzene species.)...

To clarify the effect of substituents we will discuss the spectrum of 4-nitro-benzenol, even though the compound has no value as a dye. It is a pale yellow compound ( raax 320 nm) with an ultraviolet absorption band tailing into the visible, as in Figure 28-8. Its close relatives are benzene, benzenol, and nitrobenzene ... 

The unexpected formation of the blue crystalline radical cation (97) from the reaction of triazinium salt (98) with tetracyanoethylene has been reported and the product identified by its EPR spectrum and by X-ray crystallography (Scheme 42).199 Carboxylic acids react with the photochemically produced excited state of N-t-a-phenynitrone (PBN) to furnish acyloxy spin adducts RCOOPBN. The reaction was assumed to proceed via ET oxidation of PBN to give the PBN radical cation followed by reaction with RCO2H.200 The mechanism of the protodiazoniation of 4-nitrobenzenediazonium fluoroborate to nitrobenzene in DMF has been studied.201 Trapping experiments were consistent with kinetic isotope effects calculated for the DMF radical cation. The effect of the coupling of radicals with different sulfur radical cations in diazadithiafulvalenes has been investigated.202... 

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