Crystal 1,4-dinitrobenzene

CfiHgNj. Colourless crystals m.p. 63 C, b.p. 2%TC. Turns brown in air. Prepared by a one-stage reduction of m-dinitrobenzene with iron and hydrochloric acid. 

Transfer the crude dinitrobenzene to a 250 ml. flask fitted with a reflux condenser, add 80-100 ml. of methylated (or rectified) spirit and heat on a water bath until all the crystalline solid dissolves. If the resulting solution is not quite clear, filter it through a fluted filter paper on a large funnel which has previously been warmed or through a warm Buchner funnel. Colourless crystals of m-dinitrobenzene (15 g.) are deposited on cooling. If the m.p. is below 89-90°, recrystaUisation is necessary. 

Dissolve 200 g. of sodium nitrite in 400 ml. of water in a 2-litre beaker provided with an efficient mechanical stirrer, and add 40 g. of copper powder (either the precipitated powder or copper bronze which has been washed with a little ether). Suspend the fluoborate in about 200 ml. of water and add it slowly to the well-stirred mixture. Add 4-5 ml. of ether from time to time to break the froth. The reaction is complete when all the diazonium compound has been added. Transfer the mixture to a large flask and steam distil until no more solid passes over (about 5 litres of distillate). Filter off" the crystalline solid in the steam distillate and dry upon filter paper in the air this o-dinitrobenzene (very pale yellow crystals) has m.p. 116° (t.c., is practically pure) and weighs 29 g. It may be recrystallised from alcohol the recrystallised solid melts at 116-5°. 

The filtered product is then thoroughly washed with water and crystallized from a benz or acet soln. For details see Ref 82, pp 59—61 An alternate, two-stage method of producing Tetryl is used in Germany. In the first stage dinitrome thy laniline is prepd by reacting chloro-dinitrobenzene with methylamine in the presence of Na hydroxide. In the second stage the... 

B. 2,4-Dinitrobenzenesulfenyl chloride. Dry 2,4-dinitrophenyl benzyl sulfide (232 g., 0.80 mole) and 400 ml. of dry ethylene chloride are placed in a 2-1., one-necked, round-bottomed flask equipped with a stirrer (Note 3). Sulfuryl chloride (119 g., 0.88 mole) (Note 4) is added to the resulting suspension at room temperature. A mildly exothermic reaction causes the solid to dissolve quickly, usually within 1 to 2 minutes, with a temperature rise of 10-15° (Note 5). The resulting clear yellow solution is concentrated to an oil by heating under aspirator vacuum on a steam bath (Note 6). Caution Do not heat with gas or electricity because the product, like many nitro compounds, can explode if overheated.) The residual oil is cooled to 50-60°, and 3-4 volumes of dry petroleum ether (b.p. 30-60°) are added with vigorous handswirling. The oil quickly crystallizes. The mixture is cooled to room temperature and filtered to separate 2,4-dinitrobenzene-sulfenyl chloride as a yellow crystalline solid. The sulfenyl chloride is washed well with dry petroleum ether and dried at 60-80° (Note 7) weight 150-170 g. (80-90%) m.p. 95-96° (Notes 8, 9). 

Hackel has extended Hibbert s observations concerning the influence of certain substances on the formation of nitroglycerine crystals of different forms. Thus, adding urethane, phenylurethane, collodion, nitrocotton, cyclonite, tetryl, dinitrobenzene, or centralites I and II promotes the formation of the labile form. Admixtures of siliceous earth, trinitrobenzene, TNT, favour the creation of the stable form. 

Preparation of Dinitrobemene. A mixture of 25 grams of concentrated sulfuric acid (d. 1.84) and 15 grams of nitric acid (d. 1.52) is heated in an open flask in the boiling water bath in the hood, and 10 grams of nitrobenzene is added gradually during the course of half an hour. The mixture is cooled somewhatp and drowned in cold water. The dinitrobenzene separates as a solid. It is crushed with water, washed with water, and recrystallized from alcohol or from nitric acid. Dinitrobenzene crystallizes from nitric acid in beautiful needles which are practically colorless, m.p. 90°. 

Preparation of Picric Acid (Catalytic Process). Two hundred grams of benzene in a 2-liter round-bottom flask equipped with a sealed-on condenser is refluxed on the sand bath for 7 hours with 600 cc. of nitric acid (d. 1.42) in which 10 grams of mercuric nitrate has been dissolved. The material is then transferred to another flask and distilled with steam. Benzene comes over, then nitrobenzene, then finally and slowly a mixture of dinitrobenzene and dinitrophenol. The distillation is continued until all volatile matter has been removed. The liquid in the flask is filtered hot and allowed to crystallize. If the picric acid is not sufficiently pure, it is recrystallized from hot water. 

Dissolve 6.7g (0.04 mol) of m-dinitrobenzene in 50 ml of hot methanol in a 250-ml round-bottomed flask and add, with shaking, the previously prepared methanolic solution of sodium hydrogen sulphide. Attach a reflux condenser and boil the mixture for 20 minutes ignore any further sodium carbonate which may precipitate. Allow the reaction mixture to cool and fit the condenser for distillation. Distil off most of the methanol (100-120 ml) from a water bath. Pour the liquid residue with stirring into about 200 ml of cold water. Collect the yellow crystals of m-nitroaniline by suction, wash with water and recrystallise from 75 per cent aqueous methanol. The yield of bright yellow crystals, m.p. 114 °C, is 3.7 g (69%). 

Cognate preparation, p-Dinitrobenzene. Use 34 g (0.25 mol) of p-nitroaniline (Expt 6.68) and proceed exactly as above to the point where all the suspension of p-nitrobenzenediazonium fluoroborate has been added. Filter the reaction mixture with suction, wash the residue well with water, twice with 25 ml of 5 per cent sodium hydroxide solution and finally with water. Dry the solid at 100-110°C, powder it and extract it with four 150ml portions of boiling toluene. Remove the toluene with a rotary evaporator and recrystallise the residue from about 120 ml of boiling glacial acetic acid. The yield of p-dinitrobenzene (reddish-yellow crystals), m.p. 173 °C, is 30g (71.5%). Further recrystallisation from ethanol affords pale yellow crystals of the same m.p. The p.m.r. spectrum is noted above. 

The crystals of p-dinitrobenzene (O2NC6H4NO2) are monoclinic, with two molecules per cell, C, P2ib, a0 = 11.05, b0 = 5.42, c0 = 5.65 A, and (3 = 92°18. Figure 11.19 shows that the benzene rings are centered at the comers and the center of the cell giving a body-centered cell, 3 2PTOT(m). The long direction of the molecule in the center is inclined in the opposite direction compared to those at the corners. 

The reaction of 1,3-dinitrobenzene with alkaline acetone to give a purple-coloured solution was noted as early as 1886 by Janovsky and Erb and is now known as the Janovsky reaction . Since then strong colours have been observed from a variety of active methylene compounds and the reaction is used as a test for them. Much of the literature has been summarized by Canback (1949a, 1949b), who suggested the structure 42, and more recently by Pollitt and Saunders (1965). Chemical and spectroscopic evidence is in support of formula 42 and dark purple crystals have been prepared (Gitis and Kaminskii, 1963, 1964 Kimura et al., 1965). Oxidation with hydrogen peroxide in acidic... 

Compound 50c was obtained in ca. 25% yield as a precipitate from the acid-catalyzed condensation of pyrogallol and isovaleraldehyde. No evidence of any hexamer was found in the solid material. To convert this material into the hexamer (50c)6, the original precipitate can be dissolved in Et20, acetone, or methanol, with a few drops of nitrobenzene or o-dinitrobenzene, followed by crystallization upon slow evaporation. The hexamer may also be obtained by thermal treatment of the initial precipitate or the initial filtrate. The product in the initial filtrate may be converted into hexamer by extraction in Et20, followed by evaporation to dryness with subsequent dissolution in methanol. The methanol solution is then heated to 120-150 °C for at least 12 h. Methanol may be removed under vacuum to yield a red-brown solid. Colorless hexameric spherical capsules are obtained from this solid utilizing the crystallization procedure described for the initial precipitate. 

During sulphitation a temperature of 66-73°C is maintained. After 2 hr of mixing at this temperature the contents of the vessel Me cooled to 50°C. The purified dinitrobenzene crystallizes in rather large crystals. The melting point of the product should be 88-89°C. The mother liquor is pumped off through a pipe closed... 

On the basis of the above values, Gamer and Abemethy [50] have calculated the corresponding heats of nitration (Table 45, Fig. 50). They have also determined the heats of crystallization, viz., for nitrobenzene they found a value of 2.78 kcal/mole, and for m- dinitrobenzene, 4.87 kcal/mole. 

Physical properties. Three crystalline forms of 1-chloro 2,4-dinitrobenzene are known. A stable a- modification (m. p. 53.4°C) crystallizes from nitric acid (62%) or from alcohol. An unstable, P- modification (m. p. 43 °C) can be precipitated, as Ostromyslenskii [11] reports, from a fuming nitric acid solution by treating it with water. It may also be obtained by rapid cooling of the molten substance. 

Alcoholysis of l-chloro-2,4-dinitrobenzene to 2,4-dinitroanisole. To 800 kg of methyl alcohol in the reactor 196 kg of sodium hydroxide and 600 kg of chloro-dinitrobenzene are added in 10 equal portions. The reagents are added alternately. During this operation, which requires 7 hr, a temperature at 40-45°C is maintained. Then the temperature is raised to 50°C by heating the reactor jacket and kept there for 30 min, before cooling the whole mixture to 35°C (which takes 3 hr). The crystals of the product together with the mother liquor are then transferred to a vacuum filter for separation. The product obtained is washed four times with water, centrifuged and finally transferred to the nitration plant. 

---