Systems of Metal Nitrates with Oxidizers

As known (Addison and Logan 1964), anhydrons nitrates exhibit oxidizing properties. Their oxidizing activity increases from ionic nitrates with alkali and alkali-earth metal cations to covalent nitrates with transient metal cations. Oxidation reactions result in the formation of nitrogen-containing oxides. Depending on the kind of a nitrate salt and reaction conditions, one of these oxides can be predominant. Organic snbstrates can evidently serve as reductant. 

To elevate p-selectivity in nitration of toluene is another important task. Commercial production of p-nitrotoluene up to now leads with twofold amount to the unwanted o-isomer. This stems from the statistical percentage of o m p nitration (63 3 34). Delaude et al. (1993) enumerate such a relative distribution of the unpaired electron densities in the toluene cation-radical—ipso 1/3, ortho 1/12, meta 1/12, and para 1/3. As seen, the para position is the one favored for nitration by the attack of NO (or NO2 ) radical. A procednre was described (Delande et al. 1993) that used montmorillonite clay supported copper (cupric) nitrate (claycop) in the presence of acetic anhydride (to remove excess humidity) and with carbon tetrachloride as a medinm, at room temperature. Nitrotoluene was isolated almost quantitatively with 23 1 76 ratio of ortho/meta/para mononitrotoluene. 

Using acyl nitrates as nitrating agents (compare with Section 4.5.4.2) and zeolite H-ZSM-11 treated with tributylamine, Nagy et al. (1991, 1994) were able to nitrate toluene with an even more impressive percentage of the isomers obtained—ortho 2-3%, meta 1-2%, and para 95-98%. 

Samajdar et al. (2000) performed nitration of aromatic compounds by bismnth nitrate on catalysis with montmorillonite KSF. The reaction develops in THF suspension on steering dnring 10 min. Nitration of anisole proceeds strictly in the para position (91% yield after 10 min), bnt in case of phenol, the reaction occnrs to be nonregioselective and 3 1 mixture of para and ortho nitro prod-nets is formed with a common yield of 89%. Nitration of estrone (the steroid phenol) also leads to 1 1 mixtnre of para and ortho nitrophenolic steroids in 94% yield. 

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