Copper nitrate clay-supported

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. 

Aromatic nitrations performed in the presence of KIO montmori11onite lead to increased para selectivity. With toluene as test molecule, the proportion of para-nitrotoluene reaches 79% when using clay-supported copper(II) nitrate ("claycop") in the presence of acetic anhydride under high dilution conditions in CC1 (ref. 

Novel reagents consisting of metallic nitrates impregnated on montmorillonite have been introduced in aromatic nitration. With clay-supported copper(II) nitrate in the presence of acetic anhydride it is possible to nitrate toluene quantitatively with a high para preference (79% para, 20% ortho, 1% meta). Also, good para selectivities have been found on nitration of some other aromatic hydrocarbons with copper(II) nitrate on clay. Halobenzenes are mononitrated with clay-supported copper(II) nitrate in the presence of acetic anhydride. Compared to other methods high para ortho ratios are obtained under these conditions. ... 

A. Cornells and P. Laszlo, Clay-Supported Copper (II) and Iron (III) Nitrates Novel Multi-Purpose Reagents for Organic Synthesis, Synthesis, 1985, 909. 

Cornells, A. and Laszlo, P. 1985. Clay-supported copper(II) and iron(III) nitrates Novel multipurpose reagents for organic synthesis. Synthesis. 1985(10) 909-918. 

Activation. KIO clay may be used crude, or after simple thermal activation. Its acidic properties are boosted by cation exchange (i.e. by iron(III) or zinc(II) ) or by deposition of Lewis acids, such as zinc(II) or iron(III) chloride (i.e. clayzic and clayfec ). In addition, KIO is a support of choice for reacting salts, for example nitrates of thallium(III), iron(III) ( clayfen ), or copper(II) ( claycop ). Multifarious modifications (with a commensurate number of brand names) result in a surprisingly wide range of applications coupled with the frequent imprecise identification of the clay (KIO or one of its possible substitutes mentioned above), they turn KIO into a Proteus impossible to grab and to trace exhaustively in the literature. 

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