City Research Online

Abstract

The nitration of aromatic compounds by anhydrous transition-metal nitrato compounds and oxides of nitrogen in carbon tetrachloride has been studied.

Tetranitratotitanium (IV) was found to nitrate some simple aromatic compounds of a wide range of expected reactivity in carbon tetrachloride at room temperature to give good yields of nitrocompounds. Results of direct rate measurements, competition studies and determinations of isomeric product proportions are reported. A combination of a low intermolecular selectivity and a high intramolecular selectivity of substitution was observed. A special mechanism of nitration is postulated proceeding by at least three stages of reaction and involving an intramolecular rearrangement within a co-ordination complex.

Nitro-product ratios are also reported for the reactions of the nitrato complexes of iron (III) and zirconium (IV) with some simple aromatic compounds at room temperature in the absence of solvent. The nitration of some heteroaromatic compounds by these transition-metal nitrato complexes was also investigated. Conditions were established where either 3- or mainly 4- nitropyridine was formed in the nitration of pyridine and either 7- or mainly 3- nitroquinoline produced from the nitration of quinoline.

A study of the nitration of aromatic compounds by dinitrogen pentoxide in carbon tetrachloride indicated that the nitronium ion was the effective electrophile in some reactions where previously it had been suggested that the dinitrogen pentoxide molecule itself was involved. Product isomer data and competition studies supported this idea.

The nitration of some aromatic compounds with dinitrogen tetroxide in carbon tetrachloride at room temperature was investigated. Results from competition studies and product isomer ratios are reported. For toluene, an absence of intramolecular selectivity was associated with an intermolecular selectivity very similar to that observed for nitronium ion nitrations. The importance of a radical mechanism and nitrosation is discussed as are the effects of added species.

The reactions of both dinitrogen pentoxide and dinitrogen tetroxide with aromatic compounds in carbon tetrachloride showed characteristics of inter- and intramolecular selectivity very different from those observed with tetranitratotitanium (IV), and indicated that these nitrogen oxides were not intermediates in the reactions of tetranitratotitanium (IV).

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry
Departments:	School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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