Nitro phase

Figure 11.5 Separation of normal coal-tar pitch on a nitro phase [reproduced with permission from G.P. Blumer, R. Thoms and M. Zander, Erdol Kohle, Erdgas, Petrochem., 31, 197 (1978)]. Conditions columns, two 20cm x 4mm i.d. plus a guard column stationary phase, Nucleosil NO2, Spm mobile phase, hexane-chloroform, gradient elution UV detector 300 nm sensitivity, 1 a.u.f.s. and, after 30 min, 0.4 a.u.f.s. 

The simpler nitrop>arafIins (nitromethane, nitroethane, 1- and 2-nitroproj)ane) are now cheap commercial products. They are obtained by the vapour phase nitration of the hydrocarbons a gaseous mixture of two mols of hydrocarbon and 1 mol of nitric acid vapour is passed through a narrow reaction tube at 420-476°. Thus with methane at 476° a 13 per cent, conversion into nitro methane is obtained ethane at 420° gives a 9 1 mixture of nitroethane (b.p. 114°) and nitromethane (b.p. 102°) propane at 420° afifords a 21 per cent, yield of a complex mixture of 1- (b.p. 130-6°) and 2-nitropropane (b.p. 120°), nitroethane and nitromethane, which are separated by fractional distillation. 

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. 

The use of fixed bed catalysts is described in several patents (33—37). Methods of operation include upflow, trickle bed, and even vapor phase. Typically, a large volume of solvent is used to moderate the temperature rise associated with the high heat of reaction for nitro group reduction. 

H NMR, chemical shifts, 4, 557 in nematic phase microwave spectra, 4, 537 nitration, 4, 45-46, 49, 603 nitro... 

Dissolved in alkali, extracted with ether (discarded), then the aqueous phase was acidified with hydroxylamine hydrochloride, and the nitro compound fractionally distd under reduced pressure. [Pearson and Dillon J Am Chem Soc 75 2439 1953.]... 

Other possibilities are the reduction of nitro groups by applying the sample solutions to adsorbent layers containing zinc dust and then exposing to hydrochloric acid vapors [110] 3,5-Dinitrobenzoates and 2,4-dinitrophenylhydrazones can also be reduced in the same way on tin-containing silica gel phases [111] Cellulose layers are also suitable for such reactions [112] Seiler and Rothweiler have described a method of trans-salting the alkali metal sulfates to alkali metal acetates [113]... 

Note Sulfuric acid (4%) can also be employed in place of hydrochloric acid [3]. If ammoniacal mobile phases are employed the ammonia should be removed completely (e.g. heat to 105 °C for 10 min) before dipping or spraying otherwise background discoloration can occur. The addition of titanium(III) chloride to the reagent allows also the staining of aromatic nitro compounds [6]. 

Recently, the Bartoli indole synthesis was extended to solid supports. In contrast to the earlier reports in the liquid phase, o,o-unsubstituted nitro analogs (see 25) prove to be useful substrates. In addition, fluoro/chloro substituted nitro derivatives are well tolerated, which typically undergo nucleophilic substitution under Bartoli conditions in the liquid phase. 

The use of heterogeneous catalysts in the liquid phase offers several advantages compared with homogeneous counterparts, in that it facilitates ease of recovery and recyclidg. A chro-miiun-containingmediiun-pore molecular sieve fSi Cr> 140 1, CrS-2, efficiently catalyzes the direct oxidadon of various primary amines to the corresponclmg nitro compounds using 70% r-butylhy operoxide (TBHP. ... 

Preparation of Memfield resin-bound nitro acetates, which is a suitable bndding block for the development of combinatorial solid phase synthesis, is repotted. The anion of ethyl nitro acetate is generated in DMF by an electrochemical method using Pt cathode, magnesium rod anode, and tetrabutylairunonium bromide as an electrolyte. Alkylaton of this anion with alkyl hahdes gives mono-alkylated products in 80% yield." ... 

Sodium chlorite under phase-transfer catalysis conditions ( CH,Cl,-Na0H-BmNHS04i is also a good choice for the Nef reaction of primary and secondary nitro compounds fEq. 6.10. ... 

Aromatic nitro compounds are hydrogenated very easily aliphatic nitro compounds considerably more slowly. Hydrogenations have been carried out successfully under a wide range of conditions including vapor phase (S9). Usually the goal of reduction is the amine, but at times the reduction is arrested at the intermediate hydroxylamine or oxime stage nitroso compounds never accumulate, although their transient presence may appreciably influence the course of reaction. In practice, nitro compounds often contain other reducible functions that are to be either maintained or reduced as well. 

A mixture of the foregoing nitro compound 3 (0.27 g, 1 mmol), iron powder (0.25 g, 4.5 m-atom) and HOAc (20 mL) was heated at 50 C for 5 h, cooled, diluted with H20 and extracted with CH2C12. The organic phase was washed with sat. brine, dried (MgS04) and evaporated yield 0.16 g (66%) mp 259 — 262°C. 

To a cold (0 C) solution of 5.7 mmol of the a-nitro alcohol 1 in 20 mL of CH,CI2 arc added 1.8 mL (8.1 mmol) of rm-butyldimethylsilyl trifluoroinethanesulfonate, followed by 1.2 mL (10.3 mmol) of 2,6-dimethylpyridinc. The mixture is stirred at 0 lo 1 C for 1 h, then poured into a mixture of 80 mL of Et,0 and 20 mL of water. The aqueous layer is discarded and the organic phase is washed with three 50-mL portions of water, two 30-mL portions of dil aq hydrochloric acid, then three 50-mL portions of water, dried over MgS04, and the solvent removed on a rotary evaporator. The crude product is purified by bulb-to-bulb distillation yield 60%. 

J. Tranchant, IndChimBelge 32 (Spec No), 601-5 (1967) CA 70, 49146 (1969) A gas-phase method of chromatographic analysis is described for measuring stabilizers and some of their derivatives, as well as a method for the chromatographic sepn in thin layers of nitro and... 

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