For nitrobenzene

There is increasing evidence that the ionisation of the organic indicators of the same type, and previously thought to behave similarly, depends to some degree on their specific structures, thereby diminishing the generality of the derived scales of acidity. In the present case, the assumption that nitric acid behaves like organic indicators must be open to doubt. However, the and /fp scales are so different, and the correspondence of the acidity-dependence of nitration with so much better than with Hg, that the effectiveness of the nitronium ion is firmly established. The relationship between rates of nitration and was subsequently shown to hold up to about 82 % sulphuric acid for nitrobenzene, />-chloronitrobenzene, phenyltrimethylammonium ion, and p-tolyltrimethylammonium ion, and for various other compounds. ... 

Economic Aspects. The two main areas affecting the economic aspects for nitrobenzene production are process related costs, including raw ... 

Uses. The largest end use for nitrobenzene is in the production of aniline (see Amines, AROMATIC). Approximately 95—98% of nitrobenzene is... 

Health nd Safety Factors. The mononitrochlorobenzenes are toxic substances which may be absorbed through the skin and lungs giving rise to methemoglobin. Their toxicity is about the same as or greater than that of nitrobenzene. The para isomer is less toxic than the ortho isomer, and the maximum allowable concentration that has been adopted for -nitrochlorobenzene is 1 mg/m (0.1 ppm) (6). The mononitrochlorobenzenes are moderate fire hazards when exposed to heat or flame. They ate classified by the ICC as Class-B poisons. The same handling precautions should be used for these compounds as are used for nitrobenzene. 

Manufacture and Processing. Mononitrotoluenes are produced by the nitration of toluene in a manner similar to that described for nitrobenzene. The presence of the methyl group on the aromatic ring faciUtates the nitration of toluene, as compared to that of benzene, and increases the ease of oxidation which results in undesirable by-products. Thus the nitration of toluene generally is carried out at lower temperatures than the nitration of benzene to minimize oxidative side reactions. Because toluene nitrates at a faster rate than benzene, the milder conditions also reduce the formation of dinitrotoluenes. Toluene is less soluble than benzene in the acid phase, thus vigorous agitation of the reaction mixture is necessary to maximize the interfacial area of the two phases and the mass transfer of the reactants. The rate of a typical industrial nitration can be modeled in terms of a fast reaction taking place in a zone in the aqueous phase adjacent to the interface where the reaction is diffusion controlled. 

Health and Safety Factors. The toxic effects of the mononitrotoluenes are similar to but less pronounced than those described for nitrobenzene. The maximum allowable concentration for the mononitrotoluenes is 2 ppm (11 mg/m ) (6). Mononitrotoluenes are low grade methemoglobin formers (4) and may be absorbed through the skin and respiratory tract. The toxicity of alkyl nitrobenzenes decreases with an increasing... 

The price of aniline is also dependent on the cost of benzene, the raw material for nitrobenzene. During the decade of the 1980s, benzene prices ranged from a low of 0.185/L to a high of 0.595/L. A 0.01/L change in price of benzene is roughly equivalent to a 0.01/kg change in the cost of aniline. At times aniline prices are stated on an "ex-benzene" basis to eliminate the effect of volatility in benzene prices on the price of the aniline sold. 

C. Relative reactivity and isomer distribution for nitrobenzene and the nitrotoluenes ... 

Draw the most important resonance contributors for nitrobenzene (include all of the contributors needed to explain for the variation in electrostatic potential, charge and chemical shift relative to benzene). Do these resonance contributors account for the different behavior of 6meta and 6paia Explain. 

The usual order found with halogenonitrobenzenes is F > Cl Br I, the order of Cl and Br being variable, just as in heteroaromatic reactivity. The position of fluorine is of interest the available data indicate that it is usually the same as for nitrobenzene derivatives. Thus, in acid hydrolysis the order F > Cl for 2-halogeno-quinolines can be deduced beyond doubt since the fluoro derivative appears to react in the non-protonated form and the chloro derivative to resist hydrolytic attack even in the protonated form under appropriate conditions (Section II,D, l,d). Furthermore, in the benzo-thiazole ring, fluorine is displaced by the CHgO reagent at a rate 10 times that for chlorine. ... 

Problem 16.7 Write resonance structures for nitrobenzene to show the electron-withdrawing reso-] nance effect of the nitro group. 

Baltrop and Bunce (Ref 20) employed a variety of radiation wavelengths, nitrocompds and solvents. For wavelengths less than 2900A, aniline was the main product, while above 2900A, bimolecular species such as azobenzene predominated. Since oxygen had little effect on aniline production, expts were performed in the presence of oxygen. For nitrobenzene in isopropyl alcohol, no azoxybenzene was produced as with Hurley and Testa (See above Ref 17). They concluded that the excited state abstracts H-atoms, and suggest that the nitrobenzene triplet is in tt, ti, and that nitrosobenzene is an unobserved intermediate... 

Benzoic Acid, C6H5COOH.—The treatment of benzoic acid is the same as for nitrobenzene except for the S values. The results for SQ = 4 and Sc (of the carboxyl group) = 0.8 are given in the last column of Table II it is seen that the carboxyl group, like the nitro group, is meta directing, in agreement with experiment. The calculation, however, indicates a rather too small deactivation of the meta position. This effect appears only in the third decimal place of Cmeta, and is consequently not shown in the table. 

Yeong, K. K., Gavriilidis, A., Zape, R., Hessel, V., Catalyst preparation and deactivation issues for nitrobenzene hydrogenation in a microstructured falling film reactor, Catal. Today 81, 4 (2003) 641-651. 

The EMF and SHG responses for nitrobenzene as solvent were qualitatively identical to those for l,k2-dichloroethane [Fig, 17(b)]. The only difference between the results for the two solvents was that the SHG response to KCl of nitrobenzene membranes with ionic sites was more sensitive than for 1,2-dichloroethane membranes with ionic sites, where an increase in the SHG intensity was observed at KCl activities above 10 " M KCl. 

The zinc teflate Zn(OTeF5)2 has been synthesized and characterized by IR and 19F NMR spectroscopy. The interaction with a number of weakly coordinating solvents was studied and the single-crystal X-ray structures determined for nitrobenzene derivatives [Zn(OTeF5)2 (PhN02)2]2 and Zn(0TeF5)2(PhN02)3.428... 

The heat of decomposition (238.4 kJ/mol, 3.92 kJ/g) has been calculated to give an adiabatic product temperature of 2150°C accompanied by a 24-fold pressure increase in a closed vessel [9], Dining research into the Friedel-Crafts acylation reaction of aromatic compounds (components unspecified) in nitrobenzene as solvent, it was decided to use nitromethane in place of nitrobenzene because of the lower toxicity of the former. However, because of the lower boiling point of nitromethane (101°C, against 210°C for nitrobenzene), the reactions were run in an autoclave so that the same maximum reaction temperature of 155°C could be used, but at a maximum pressure of 10 bar. The reaction mixture was heated to 150°C and maintained there for 10 minutes, when a rapidly accelerating increase in temperature was noticed, and at 160°C the lid of the autoclave was blown off as decomposition accelerated to explosion [10], Impurities present in the commercial solvent are listed, and a recommended purification procedure is described [11]. The thermal decomposition of nitromethane under supercritical conditions has been studied [12], The effects of very high pressure and of temperature on the physical properties, chemical reactivity and thermal decomposition of nitromethane have been studied, and a mechanism for the bimolecular decomposition (to ammonium formate and water) identified [13], Solid nitromethane apparently has different susceptibility to detonation according to the orientation of the crystal, a theoretical model is advanced [14], Nitromethane actually finds employment as an explosive [15],... 

The water-gas shift rates are obviously much lower when heterogenized in comparison with the Rh complexes in homogeneous solutions of the amines (also see Tables 30-33). Kinetics for nitrobenzene reduction were performed for the cis-[Rh(CO)2(2-picoline)2]PF6 catalyst, and reported in 2000. Kinetics displayed a first order dependence on Pco over the range 0-1.9 atm in the temperature range 80-120 °C. As with the kinetics previously reported by Lima Neto and coworkers,121 it was suggested that the CO addition preceded the rate limiting step. A non-linear dependence on the rate versus Rh concentration, as with the previous study, suggested participation by both mononuclear and polynuclear species. 

When the nitroparaffins are reduced with powerful agents, the corresponding amines are formed in a way similar to that described in the next section for nitrobenzene. But just as in the case of nitrobenzene, so also with nitroparaffins, the reaction can be stopped at the hydroxylamine stage by using zinc dust in a neutral medium. 

Because of the opposite nature of the n interactions between the ring and either the nitro or the amino substituent, let us assess the stabilization energies of nitrobenzene and aniline. In equation 13, the resonance stabilizing energy of aniline was defined as the exothermicity of a reaction involving arbitrary reference states. By analogy to equation 13, we may write equation 57 for nitrobenzene and the same arbitrary reference states, R = /-Pr or t-Bu. 

Both CIDNP and ESR techniques were used to study the mechanism for the photoreduction of 4-cyano-l-nitrobenzene in 2-propanol5. Evidence was obtained for hydrogen abstractions by triplet excited nitrobenzene moieties and for the existence of ArNHO, Ai N( )211 and hydroxyl amines. Time-resolved ESR experiments have also been carried out to elucidate the initial process in the photochemical reduction of aromatic nitro compounds6. CIDEP (chemically induced dynamic electron polarization) effects were observed for nitrobenzene anion radicals in the presence of triethylamine and the triplet mechanism was confirmed. 

Nitrobenzene, 2,4-dinitrotoluene and 2,6-dinitrotoluene were determined in water by GC-EC or GC-CLD thermal energy analyzer (TEA) and by EI-MS, CI-MS and NICI-MS455, after solid-phase microextraction (SPME) with polydimethylsiloxane coated fiber. SPME is a technique to concentrate organic compounds dissolved in an aqueous matrix by adsorption on a solid stationary phase immobilized on a fused silica fiber. The analytes were thermally desorbed directly into the GC injector LOD was 9 pg/L for nitrobenzene and 15 pg/L for the dinitrotoluenes456. 

Details of nitrobenzene photochemistry reported by Testa are consistent with the proposal that the lowest triplet excited state is the reactive species. Photoreduction, as measured by disappearance quantum yields of nitrobenzene in 2-propanol is not very efficient = (1.14 0.08) 10 2 iD. On the other hand, the triplet yield of nitro benzene in benzene, as determined by the triplet-counting method of Lamola and Hammond 28) is 0.67 0.10 2). This raises the question of the cause of inefficiency in photoreduction. Whereas Lewis and Kasha 29) report the observation of nitrobenzene phosphorescence, no long-lived emission from carefully purified nitrobenzene could be detected by other authors i4,3o). Unfortunately, the hterature value of Et for nitrobenzene (60 kcal mole i) is thus based on an impurity emission and at best a value between 60 and 66 kcal mole can be envisaged from energy-transfer experiments... 

In view of the short lifetime ( 10 s), which has been reported for nitrobenzene and might be expected for similar nitroaromatics with low lying (n, 7T ) states, and since intramolecular hydrogen abstractions from benzylic positions take place, lack of oxygen quenching may be inconclusive. 

Quenching studies on the photolysis of 14 (R = C(CH3)3) using 1,3-pentadiene reveal that even at 2.5 mole pentadiene not all excited states are quenched >, thus at present a triplet state as reacting excited state cannot be regarded as proven for the direct irradiations although it seems likely in view of the high triplet yield reported for nitrobenzene. 

The quantum yield for formation of 20, R=6-C(CH3)3, from 14, R=4-C(CH3)3, via photolysis in fer -butyl alcohol and oxidative workup, has been determined as (1.2 0.1) X 10 2 4 ). Quantum yields for formation of various other N-hydroxy-2-indolinones from appropriately substituted 2-nitro-fer -butylben-zenes fall into the range 1.1 X 10 to 2.2 X 10 and thus are of the same order of magnitude as the disappearance quantum yield reported for nitrobenzene in 2-propanol... 

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