Nitrobenzene reaction products/yields

The reaction product, which is a dark reddish-brown liquid, is poured or siphoned (Note 5) into 1.5 1. of water to which 50 cc. of a saturated solution of sodium bisulfite has been added (Note 6). The mixture is distilled with steam (Org. Syn. 2, 80) and the first portion of the distillate is collected separately to remove a small amount of unchanged nitrobenzene. It is necessary to collect about 12 1. of distillate in order to obtain all of the m-bromonitrobenzene. The yellow crystalline solid is filtered with suction and pressed well on the funnel to remove water and traces of nitrobenzene. The yield of crude product varies from 270-340 g. (60-75 Per cent °f the theoretical amount). It melts at 51.5-520 and boils at 117-118 79 mm. This product is satisfactory for most purposes. If a purer material is desired, the crude /w-bromonitrobenzene may be distilled under reduced pressure. The recovery on purification is about 85 per cent. Briihl recorded the b.p. as 1380/18 mm. and the m.p. as 56° for pure wz-bromonitrobenzene.1... 

Since no relatively stable free radical is present (such as 26 in 14-17), most of the product arises from dimerization and disproportionation. The addition of a small amount of nitrobenzene increases the yield of arylation product because the nitrobenzene is converted to diphenyl nitroxide, which abstracts the hydrogen from 1 and reduces the extent of side reactions. ... 

Protein B from M. capsulatus (Bath) not only increases the product yields, but also influences the rate constant for the single turnover reaction of Hred with nitrobenzene (51,67). The pseudo-first-order rate constant increases up to 33-fold when Hred is titrated with protein B. Neither addition of reductase to Hox or Hred, nor addition of protein B and reductase to Hred, could similarly affect the rate constant. These... 

The yields of reaction products from thermal nucleophilic substitution reactions in DMSO of 0- and p-nitrohalobenzenes (Zhang et al. 1993) or p-dinitrobenzene (Liu et al. 2002) with the sodium salt of ethyl a-cyanoacetate were found to be markedly diminished from the addition of small amounts of strong electron acceptors such as nitrobenzenes. At the same time, little or no diminution effects on the yields of the reaction products were observed from the addition of radical traps such as nitroxyls. These results are consistent with the conclusion that such reactions proceed via a nonchain radical nucleophilic substitution mechanism (Scheme 4.26). 

Gas chromatographic examination of another reaction mixture run on a 10-mmol scale with undecane as an internal standard indicates that 2-methyl-4 -nitrobipheny1 is formed in 90% yield based on l-bromo-4-nitrobenzene. The product obtained by this procedure shows the following properties mp 99-101 C (lit., mp 103-105°C) IR (neat) cm l 1600 (s), 1510 (s), 1480 (s), 1340 (s),... 

Chlorpromazine and other phenothiazines can be identified by their reactions with benzene-, toluene-o-, and toluene /j-stilbinic acids, and with p-hydroxy-, m-nitro-, w-amino-, and p-nitrobenzene stilbinic acids in an HCl medium. The reaction products are initially colorless masses but rapidly oxidize to yield colored products [32]. 

It is rather important to note that if an aromatic nitro compound is the substance being nitrated, addition of mercuric nitrate to the nitric acid has no effect on the reaction. For example, nitrobenzene is nitrated to dinitrobezene in the same yield both in the presence of a mercury salt and in its absence. This can be explained by the fact that nitro compounds such as nitrobenzene do not yield addition product with mercuric salts. 

The reaction of a thioamide or thiourea and an A/,(V-dimethylacylamide dimethyl acetal at room temperatures produces imino derivatives of type (327). The latter compounds readily condense with amino transfer reagents such as hydroxylamine-O-sulfonic acid and mesitylsulfonyloxyamine (MSH) to afford (301 R=H, Me R = aryl, ArNH, 4-pyridyl) in excellent yields. An unusual reaction of the E category is the condensation of nitrosobenzene with thiobenzoyl isocyanate, which produces the thiadiazolone (328) in 58% yield (Scheme 118) (73CB1496). Presumably, nitrobenzene is another reaction product, although this has not been characterized. 

The simpler iron carbonyls, Fe(CO)5 and Fe2(CO)9, can also deoxygenate nitrobenzenes to anilines in an aqueous base-organic solvent system. With these carbonyls, however, a phase-transfer catalyst is not only unnecessary, its presence results in reduced product yields Furthermore, the nitro compound must be present to induce attack of hydroxide ion on Fe(CO)s t0 give HFe(CO)4 [and possibly HFe2(CO)8 ] (77). Such a phenomenon was also noted by Pettit and co-workers (23) in their excellent work on the use of water gas shift reaction conditions for the Fe(CO)5-cat-alyzed deoxygenation of nitrobenzenes. 

PEI-RhCl3 and PEI-RUCI3 complexes exhibit different catalytic activity with regard to a mixture of the cis- and trans isomers of pentadiene [61]. The former complex is more selective for pentene (0.94) than the latter. A quantitative aniline yield results from the reduction of nitrobenzene in the presence of PEI complexes with Ni(II), Co(ll), Sn(II), Pd(II) and Rh(III) [61]. The reduction proceeds rapidly at 20- 70°C and at 1-25 atm pressure of H2 both in a solvent and without. Besides aniline, cyclohex-ylamine is produced by further hydrogenation of the aromatic ring in the presence of the PEI-Rh(III) complex. Polymer-metal catalysts do not lose their catalytic stability after repeated application. For example, when eight hydrogenation reactions were catalyzed with PEI-Pd(II), in each case a 100% product yield of aniline was attained. 

That water has a profound effect on product yield and selectivity was demonstrated by a series of reactions that contained varying amounts of protic material. Thus, as the amount of water was increased in the reaction, the conversion of nitrobenzene decreased dramatically. However, increasing the amount of water also resulted in reactions which displayed a higher degree of selectivity to the desired... 

The blue-colored reaction product was washed thoroughly with ethanol (to remove nitrobenzene), boiled for 5 min with 1 M HCl saturated with NaCl and filtered after coiling. Then the residue was treated with 50 mL 1 M NaOH containing 20 g NaCl at 90 °C until no more ammonia was evolved. The product was treated again after filtration with 1 M HCl and 1 M NaOH, and then thoroughly washed with water. Finally, the tetranitrophthalocyanine was treated for 24 h with methanol, then for 24 h with acetone in a Soxhlet apparatus and dried. Yield 3.2 g (97%). IR (in KBr) 1612, 1521, 1338, 825, 753 cm. UV-vis in H2SO4 at A, 766, 633, 307 nm. 

Ragaini and colleagues recently studied the influences of acid additives [20-22]. Using the palladium-phenanthroline catalyst system for the carbonylation of nitrobenzene to methyl phenylcarbamate, the addition of anthraniUc acid [20] or phosphorus acids [21, 22] can accelerate the reaction. Anthranilic acid produced higher activity compared with the use of simple benzoic acid. The 4-amino isomer does not show the same increased activity. Later on, they established an improved catalytic system for the carbonylation of nitrobenzene by adding phosphoms acids as an additive, for the first time yielding activities and catalyst fife in the range necessary for industrial applications. By pafladium-phenanthroline complexes and phosphorus acids as promoters, nitrobenzene was carbonylated to methyl phenylcarbamate with unprecedented reaction rates (TOP up to 6,000/h) and catalyst sta-bUity (TON up to 10 ). The best promoter was phosphoric acid, which is very cheap, nontoxic and easily separable from the reaction products. The catalyst system was also applied to the economically very important dinitrotoluenes reduction. 

Koga has shown that by using diphenylmethane and 1,2-diphenyl-ethane, modest yields of the p,/ -disubstituted products also can be obtained. Since the reaction was run using excess AICI3 and the yields are modest, one wonders about the contribution by products analogous to 133. Among the solvents tried were chlorinated hydrocarbons, CS2, and nitrobenzene. The best yields were obtained using 1,2-dichloroethane. 

Following the VNS mechanism, the first step of the reaction is the nucleophilic addition of the enolate of ethyl 2-cloropropionate to the nitrobenzene ring (the ester forms the enolate in the reaction medium in the presence of NaH). As stated above, the ortho/para selectivity in VNS reactions is controlled by steric factors. Hence, a tertiary carbanion like 8 would attack exclusively in the para-position leading to o-adduct 9. The next step will be the base-induced elimination of HCl in 9 to yield anion intermediate 10, which is trapped by the electrophile (benzyl bromide) giving the reaction product 11 (Scheme 36.6). 

As can be seen from Table 19, other nitrogen-containing heterocycles like pyrrole, pyrazole, indole, and piperidine gave the corresponding A-arylated products with l-chloro-4-nitrobenzene and l-fluoro-4-nitrobenzene in excellent yields. Lower reaction rates but comparable yields were observed with resin supported 1 compared to its homogeneous counterpart. The resin supported 1 can be recovered by simple filtration and reused for three cycles with consistent activity. 

A brief account of aromatic substitution may be usefully given here as it will assist the student in predicting the orientation of disubstituted benzene derivatives produced in the different substitution reactions. For the nitration of nitrobenzene the substance must be heated with a mixture of fuming nitric acid and concentrated sulphuric acid the product is largely ni-dinitrobenzene (about 90 per cent.), accompanied by a little o-dinitrobenzene (about 5 per cent.) which is eliminated in the recrystallisation process. On the other hand phenol can be easily nitrated with dilute nitric acid to yield a mixture of ortho and para nitrophenols. It may be said, therefore, that orientation is meta with the... 

The commercial product, m.p. 53-55°, may be used. Alternatively the methyl -naphthyl ketone may be prepared from naphthalene as described in Section IV,136. The Friedel - Crafts reaction in nitrobenzene solution yields about 90 per cent, of the p-ketone and 10 per cent, of the a-ketone in carbon disulphide solution at — 15°, the proportions ore 65 per cent, of the a- and 35 per cent, of the p-isomer. With chlorobenzene ns the reaction medium, a high proportion of the a-ketone is also formed. Separation of the liquid a-isomer from the solid p-isomer in Such mixtures (which remain liquid at the ordinary temp>erature) is readily effected through the picrates the picrate of the liquid a-aceto compound is less soluble and the higher melting. 

Reaction of 1 2 3 tribromo 5 nitrobenzene with sodium ethox in ethanol gave a single product CsHyBrjNOs m quantitative yield Suggest... 

The reduction of the nitro group to yield aniline is the most commercially important reaction of nitrobenzene. Usually the reaction is carried out by the catalytic hydrogenation of nitrobenzene, either in the gas phase or in solution, or by using iron borings and dilute hydrochloric acid (the Bechamp process). Depending on the conditions, the reduction of nitrobenzene can lead to a variety of products. The series of reduction products is shown in Figure 1 (see Amines byreduction). Nitrosobenzene, /V-pbenylbydroxylamine, and aniline are primary reduction products. Azoxybenzene is formed by the condensation of nitrosobenzene and /V-pbenylbydroxylamine in alkaline solutions, and azoxybenzene can be reduced to form azobenzene and hydrazobenzene. The reduction products of nitrobenzene under various conditions ate given in Table 2. 

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