Toluene nitration, chemistry

Bakke et al. (1982) have shown how montmorillonite catalyses chlorination and nitration of toluene nitration leads to 56 % para and 41 % ortho derivative compared to approximately 40 % para and 60 % ortho derivatives in the absence of the catalyst. Montmorillonite clays have an acidity comparable to nitric acid / sulphuric acid mixtures and the use of iron-exchanged material (Clayfen) gives a remarkable improvement in the para, ortho ratio in the nitration of phenols. The nitration of estrones, which is relevant in making various estrogenic drugs, can be improved in a remarkable way by using molecular engineered layer structures (MELS), while a reduction in the cost by a factor of six has been indicated. With a Clayfen type catalyst, it seems possible to manipulate the para, ortho ratio drastically for a variety of substrates and this should be useful in the manufacture of fine chemicals. In principle, such catalysts may approach biomimetic chemistry our ability to predict selectivity is very limited. 

The major uses of toluene are in high-octane (Pb-free) motor fuels, paints, dyes, plastics, detergents and expls. The usual route to useful expls is by the nitration of toluene to mono-, di-, and trinitro derivatives. See also in Vol 8, N40-R ff under Nitration , and N211-L R under Nuclear Tracers in Explosive Chemistry ... 

Displaying a grasp of chemistry remarkable even among chemical engineers, the authors ascribe the hazardous side reaction consequent upon mono-nitration of toluene in mixed acid, to a decomposition of nitric acid (science has hitherto regarded nitric acid as thermodynamically more stable than conceivable decomposition products). This is favoured by poor mixing in what they describe as a three phase mixture (m/xo-nitrotoluenes being apparently immiscible with toluene). What the calorimetric study described seems to have observed is the transition from nitration to oxidation of the substrate. 

First, one of the classical reactions of aromatic chemistry the nitration of toluene. The methyl group directs the nitration to the para position, so we get the right substitution pattern for benzocaine. But we also get the wrong oxidation levels first, the nitro group needs reducing to NH2 this can be done with catalytic hydrogenation (Chapters 22 and 24). 

All industrial polyurethane chemistry is based on only a few types of basic isocyanates. The most significant aromatic diisocyanates are TDI and MD. TDI is derived from toluene. This is initially nitrated to dinitrotoluene, then hydrogenated to diamine, and finally phosgenated to diisocyanate. A defined mixture of isomers comprising toluene-2,4-and 2,6-diisocyanate is obtained. Approximately 1.3 million tons/year of TDI are produced world-wide, most of which is used in the production of polyurethane flexible foam materials. 

Kinugasa et al. [98,111] noted that in the case of aliphatic hydrocarbons, the ELM becomes more stable with increasing number of carbon atoms, while those composed of aromatics, such as toluene, were less stable to mechanical forces. Lin and Long [44] found kerosene to be the more efficient diluent than S lOON for nitrate extraction. Kumbasar and Tutkun [112] report that kerosene is a better-performing diluent than STA90 NS for gallium removal by ELM. Lee et al. [41] studied several diluents for europium extraction and report that while n-dodecane and kerosene are somewhat similar, xylene demonstrated much lower extraction efficiency. They speculate that the difference may be due to the steric chemistry and polarity effects imposed on the carrier, in this case PC 88A. 

In addition to the reaction schemes described earlier, there are many other types of systems that are quite common. In one of these, a single reactant may be converted into several different products simultaneously. There are numerous examples of such reactions in organic chemistry. For example, the reaction of toluene with bromine in the presence of iron at 25°C produces 65% p-bromotoluene and 35% o—bromotoluene. Similarly, the nitration of toluene imder different conditions can lead to different amounts of o—nitrotoluene and p-nitrotoluene, but a mixture of these products is obtained in any event. Tailoring the conditions of a reaction to obtain the most favorable distribution of products is a common practice in synthetic chemistry. We will now illustrate the mathematical analysis of the kinetics of such reactions. 

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