O- and p-Nitrotoluene

One way to assess the relative stabilities of these var ious intermediates is to examine electron delocalization in them using a resonance description. The cyclohexadienyl cations leading to o- and p-nitrotoluene have tertiar y car bocation character. Each has a resonance form in which the positive charge resides on the carbon that bear s the methyl group. 

Nitration of toluene is the only important reaction that involves the aromatic ring rather than the aliphatic methyl group. The nitration reaction occurs with an electrophilic substitution hy the nitronium ion. The reaction conditions are milder than those for henzene due to the activation of the ring hy the methyl substituent. A mixture of nitrotoluenes results. The two important monosubstituted nitrotoluenes are o- and p-nitrotoluenes ... 

Fig 7a Influence of temperature on the yield of DNT, Nitration of o- and p-nitrotoluenes in nitrating mixtures with various concentrations of sulfuric acid (Kobe, Skinner and Prindle, Ref 45)... 

The various derivatives of o- and p-nitrotoluene are the most familiar class of compounds which can be considered vinylogous nitromethanes. Due to the low solubility in water of most of the compounds belonging to this class, pK values have been determined in aqueous-organic solvents. The availability of many pK scales in these solvent mixtures and the possibility of relating the relative acidities to the pKa scale has been discussed202. Some equilibrium constants are shown in Table 20. 

While the direct halogenation of toluene gives a mixture of isomers that is difficult to separate into the pure isomers, the isomeric o- and p-nitrotoluenes 6a and 6b, formed by nitration, are easy to separate from each other. Thus reduction of the single o- or p-nitrotoluene 6 to the o- or p-toluidine 7a or 7b respectively, followed by conversion into the corresponding diazonium salt 8 and a subsequent Sandmeyer reaction leads to the pure o- or p-halotoluene 9. 

Additives used by the US Naval Ordnance Test Station, Inyokern, Calif included 0.5 to 1.0% a-MNN, 0.5% catechol, 0.25% anthracene and 0.25 to 0.75% Span 80A. In addition, small percentages of o- and p-nitrotoluene mixts, such as 3.36/1 were found to be effective. However, the high-melting eutecticforming additives anthracene, a-MNN and cathechol were preferred because little exudation occurred at temps up to within ca 5° of the eutectic temp... 

Preparation 226.—o- and p-Nitrotoluenes (l-Methyl-2-nitrobenzene and 1 -methyl-i-nitrobenzene). 

Urbanski (Ref 53) also studied the effect of addition of such non-solvent liqs as H20, C7H14, CHO3, iso-CsHuOH, glycerol, castor oil, o-and p-nitrotoluene, PhNH2, and glycerol triacetate, on the deton rate of RDX. He also found that as liq content increased, the D vs %liq curve passes thru a max. Kegler (Ref 65) investigated the effect of the addition of w and aq solns of amm nitrate or hydroxide, hydrazine or nitric acid on the D of RDX. Unfortunately his data are unavailable to us... 

The mixture of o- and p- nitrotoluene they obtained was free from the m- isomer. The authors used it for further nitration, Mid found that the resulting trinitrotoluene was of much higher purity than that produced from mononitrotoluene according to the conventional industrial method. 

Recently Kobe, Skinner and Prindle [32] reported their extensive studies on the nitration of o- and p- nitrotoluenes to dinitrotoluene. They concluded that the most favourable parameters of the nitration of o- and p- nitrotoluenes differed somewhat from each other. Thus the concentration of mixtures for nitrating o- nitro-toluene might vary within a wider range, especially with regard to the quantity of sulphuric acid. Also, lower temperatures may be applied for the nitration of o- nitrotoluene. 

Figures 59, 60 and 61 show the influence of temperature and concentration of sulphuric acid on the yield of dinitrotoluene using o and p- nitrotoluene as starting materials.

The sepMation of the production unit of mononitrotoluene from the next stages of nitration is desirable so as to provide the mononitration unit with a unit for removing m-nitrotoluene by distillation. A mixture of o and p- nitrotoluene or o- nitrotoluene alone is then used for further nitration. In the latter case p- nitrotoluene is utilized for the preparation of dyes (from p- toluidine, derivatives of stilbene, etc.) and pharmaceuticals (p- aminobenzoic acid.)... 

Mononitration of benzene is carried out at about 60° and dinitration meta isomer) at about 95° further nitration is difficult. In a similar manner, toluene gives rise to o- and p-nitrotoluenes (90%) and a small quantity of the meta isomer, isopropylbenzene (cumene) goes predominantly to p-nitrocumene (89%), and t-butylbenzene to p-nitro-t-butyl-benzene (74%). For the nitration of an easily oxidizable substance like p-cymene, a good emulsion and careful temperature control are important. ... 

Trinitrotoluene was prepared by Wilbrand in 1863 by the nitration of toluene with mixed acid, and in 1870 by Beilstein and Kuhlberg by the nitration of o- and p-nitrotoluene, and by Tiemann by the nitration of 2,4-dinitrotoluene. In 1891 Haus-sermann with the Griesheim Chem. Fabrik undertook its manufacture on an industrial scale. After 1901 its use as a military explosive soon became general among the great nations. In the first World AVar all of them were using it,... 

The treatment of o and p-nitrotoluenes with a basic agent (e.g. potassium / butoxide) in the absence of air can give rise to oxidation of nitrobenzyl radica anions which further react to yield dinitrodibenzyl [102]. The reaction can pro ceed through a radical chain mechanism [103] (23) ... 

It is generally known that 2 4 dinitrotoluene is formed by nitration of o-and p-nitrotoluene and 2.6-dinitro isomer by nitration of o nitrotoluene. ft was accepted that 2.3% 3.4- and 3.6-isomers are produced from m-nitroioluene. Nevertheless it was firmly established that the nitration ofo and p-nitrotoluenc can also produce a small proportion (below 0.5%) of 2.. - and 3,4-dinitrotoluene respectively (33).. Mso small proportions of other isomeric dinitrotoluenes, such as 2,3-, 2,5- and 3.4- was proved from c - and p-nitrotoluene respectively 134). Milt and co workers [39] have found that the nitration of pure o- and p-nitro-toiuene at —lO C with a nitrating mixture containing SOj yielded only 0. % dinitro- and trinitroproducts deriving from m nitroto1uene. 

Nitrotoluenes are intermediates for dyes, pharmaceuticals, and perfumes, and precursors for the explosive 2,4,6—trinitrotoluene (TNT). A mixture of o-and p-nitrotoluene can be nitrated to dinitrotoluenes, the feedstocks for the manufacture of diisocyanates. The isomeric 2,4— and 2,6-dinitrotoluenes are obtained in a ratio of roughly 80 20... 

History of the Preparation of the Dinitrotolu-enes. Urbafiski (Ref 13, pp 285—86) reports that ... The principal reaction products in the nitration of toluene are the isomers 2,4- formed from o- and p-nitrotoluenes, and 2,6- formed from omitrotoluene. From m-nitrotoluene the 23-, 3,4- and 3,6-isomers are formed,. .. 

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