1,2-Dinitrobenzene

Caution 1,2-Dinitrobenzene is a high explosive that is known to detonate when subjected to shock or temperature above its melting point [9]. To reduce the potential hazards in this experiment, less reactive 1 was used. To a slurry of 1 (0.2054g, 29.6mmol of lithium 0.4344g, 3.4mmol of naphthalene 1.7683 g, 

6 mmol of cobalt chloride) was added a solution of 0.4740 g (2.8 mmol) of 

2- dinitrobenzene in 40 ml of glyme at 0°C over a period of about 3h. The mixture was warmed to room temperature and stirred for 4h. TLC analysis showed only naphthalene, 1,2-dinitrobenzene, and an unknown material with a strong blue fluorescence (also observed in the reaction of 2 with PhN02). 

The solvent was removed, and the metal slurry washed several times with fresh portions of glyme. Water-diethyl ether extractions of the combined portions of glyme eventually yielded 0.3476 g of crystals. These were shown by TLC to be a mixture of naphthalene and 1,2-dinitrobenzene. 

Reaction of Cobalt with CeFsl Preparation of (CeF5)2Co-2PEt3 

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. 

200 cc. of water. Filter by suction, and wash twice with water. Dissolve the dinitrobenzene in 40 cc. of hot alcohol and set aside to crystallize. Filter off the crystals by suction and wash with 10 cc. of cold alcohol. Dry the crystals on a porous plate, and determine their melting-point. By adding 10 cc. of water to the filtrate a small additional amount of dinitrobenzene can be obtained. Calculate the percentage yield. 

—Small quantities of benzene and other hydrocarbons can be readily identified by converting them into solid nitro derivatives the melting-points of which can be determined. As little as 2 or 3 drops of benzene is sufficient for the identification of the hydrocarbon in this way. In working with such a small quantity proceed as follows Mix 3 drops of benzene and 1 cc. each of concentrated sulphuric acid and concentrated nitric acid. Boil the mixture for one-half minute. Cool, and pour slowly into 10 cc. of water. Shake, filter by suction ( 42, page 29), and wash with water. Dissolve in a boiling mixture of 4 cc. of water and 4 cc. of alcohol. Set aside to crystallize, filter, wash with 5 cc. of cold 50 per cent alcohol, and dry on a porous plate. The compound prepared in this way melts at 89°-89.5°. 

The acids are mixed in a flask (500 c.c.), and the nitrobenzene added in portions of 5—10 c.c. at a time. Heat is evolved, and the mass becomes somewhat deeper in colour. When the nitrobenzene has been added, the flask is heated for a shoit time on the water-bath. K few drops are then potiied into a test-tube of water. The dinitrobenzene should, if the reaction is complete, separate out as a hard pale yellow cake If it is semi-sohd, the heating must be continued. The contents of the flask are then poured, whilst warm, into a large quantity of water. The dinitrobenzene, which separates out, is filteied at the punap and well washed with water. It is then dried. The yield is nearly theoretical. A few grams should be recrystallised from spirit. The remainder may be used for the next preparation without further puiification. 

To a mixture of 14 c.c. (25 g.) of concentrated sulphuric acid and 10 c.c. (15 g.) of fuming nitric acid in an open flask 10 g. of nitrobenzene are gradually added (fume chamber). The mixture is then heated on the water bath for half an hour with frequent shaking. The reaction mixture is cooled somewhat and then poured with stirring into cold water. The dinitrobenzene solidifies, is filtered with suction, washed with water, pressed on porous plate, and crystallised from alcohol. Melting point 90°. Yield 10-12 g. 

The property of yielding nitro-derivatives by the action of nitric acid is a characteristic of aromatic substances. According to the conditions under which the nitration is carried out one or more nitro-groups can be introduced. Write the equation for the reaction. 

If an aromatic compound contains saturated aliphatic side chains nitration carried out under the above conditions takes place always in the benzene nucleus and not in the side chain. Since the carbon atoms of benzene are each united directly to only one hydrogen atom, the nitro-derivatives obtained are tertiary and therefore incapable of forming salts, nitrolic acids, or pseudonitroles, as do the primary and secondary nitro-compounds. 

1 In large-scale practice the residual nitrating acid is recovered in a similar way 1-5 moles of nitric acid are used in the present case. 

Nitro-groups can also be introduced into side chains.1 If toluene or ethylbenzene, for example, is heated with dilute nitric acid (d. 1-076) in a closed vessel to a temperature somewhat over 100° phenylnitro-methane C 6Hs.CH2.N02 or phenylnitroethane C6H5.CH(N02).CH3 is obtained. 

Dissolve 34 g. of o-nitroaniline in a warm mixture of 63 ml. of concentrated hydrochloric acid and 63 ml. of water contained in a 600 ml. beaker. Place the beaker in an ice - salt bath, and cool to 0-6° whilst stirring mechanically the o-nitroaniline hydrochloride will separate in a finely-divided crystalline form. Add a cold solution of 18 g. of sodium nitrite in 40 ml. of water slowly and with stirring to an end point with potassium iodide starch paper do not allow the temperature to rise above 5-7. Introduce, whilst stirring vigorously, a solution of 40 g. of sodium borofluoride in 80 ml. of water. Stir for a further 10 minutes, and filter the solid diazonium fiuoborate with suction on a sintered glass funnel. Wash it immediately once with 25 ml. of cold 5 per cent, sodium borofluoride solution, then twice with 15 ml. portions of rectified (or methylated) spirit and several times with ether in each washing stir 

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 weU-stirred mixture. Add 4-6 ml. of ether fiom time to time to break the froth. The reaction is complete when aU the diazonium compound has been added. Transfer the mixture to a large flask and steam distil until no more solid passes over (about 6 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° (i.e., is practically pure) and weighs 29 g. It may be recrystallised from alcohol the recrystaUised solid melts at 116-6°. 

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Perfluoroalkyl carbanions, generated by reversible nucleophilic addition of a fluoride anion to fluoroalkenes, react with dry benzenediazonium chloride in dimethyl formamide, giving phenylazoperfluoroalkanes in 41-53% yield (Dyatkin et al., 1972). The dianion obtained from 1,2-dinitrobenzene with dipotassium cyclo-octatetraenide reacts in a complex way with arenediazonium salts, forming 4-aryl-azo-2-nitrophenol in 46-58% yield (Todres et al., 1988). 

Synthetic pyrethroids with a-cyano ester group react with sodium hydroxide to yield hydrogen cyanide, which reacts with 4-nitrobenzaldehyde and 1,2-dinitrobenzene to yield a pink-colored derivative (o-quinonoid di-anion) according to the following scheme ... 

The SNAr reaction followed by intramolecular cyclization provides a useful method for the preparation of heterocyclic compounds, as summarized in Ref. 1. Reaction of 1-fluoronitroben-zene or 1,2-dinitrobenzene with guanidine in hot THF followed by treatment with t-BuOK gives 3-amino-1,2,4-benzotriazene 1-oxide in good yield (Eq. 9.11).19... 

Choice of a suitable solvent, preferably of high polarity, such as PhN02 or sulpholane and for low temperatures S02 or eutectic mixtures of PhNOz with 1,2-dinitrobenzene or nitrotoluenes. [Author s note (2002) Disregard this bad advice )... 

Similar rate accelerations due to the addition of small amounts of DMSO were found in the reactions of 1,2-dinitrobenzene with butylamine in benzene. While the reaction is almost insensitive to other additives, the accelerations observed upon addition of DMSO to benzene exceed expectations based only on considerations of the polarity of the medium9. Catalysis by other HBA additives was recently studied by Hirst and coworkers162 in connection with the homo-/hetero-conjugate mechanism . 

Chemical/Physical. Releases toxic nitrogen oxides when heated to decomposition (Sax and Lewis, 1987). 1,2-Dinitrobenzene will not hydrolyze in water (Kollig, 1993). 

Dinitrobenzene, see 1,3-Dinitrobenzene m-Dinitrobenzene, see 1,3-Dinitrobenzene o-Dinitrobenzene, see 1,2-Dinitrobenzene p-Dinitrobenzene, see 1,4-Dinitrobenzene... 

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