The nitration of m- and p-cresol was investigated under mild reaction conditions in a number of solvents; the effects of certain nitration catalysts were also evaluated. These different reaction parameters were evaluated in terms of their effect on a number of important reaction responses. Other important factors that were investigated were the manipulation of the isomer ratios by changing reaction parameters, as well as important process chemistry information, such as product distribution, isolation and purification, identification of side products formed, and evaluation of the heat of reaction. Use was made of an experimental design system to evaluate the effect of reaction parameters on the chosen design responses. It was found that the ratio of para to ortho nitrocresol products could be influenced slightly by using low concentrations of nitric acid and low reaction temperatures. A different mechanism for the formation of 2-methyl-1,4-benzoquinone (from mcresol nitration) was proposed (compared with that previously reported), which could explain a “one mole nitric acid” pathway and the fact that only the pbenzoquinone isomer was observed. Reaction side products were identified and found to consist of dimers of cresol and nitrocresol, which were probably the result of oxidation of the cresol, subsequent formation of a quinomethide intermediate and reaction with either the product or the substrate. The heat of nitration was determined for various reaction systems and found to be governed by two factors, namely the actual nitration process and also an oxidation process, which is responsible for the formation of side products.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nmmu/vital:10957 |
| Date | January 2001 |
| Creators | Van Niekerk, Rudolf Jacob Francois |
| Publisher | Port Elizabeth Technikon, Faculty of Applied Science |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis, Masters, MTech (Chemistry) |
| Format | ix, 154 leaves, pdf |
| Rights | Nelson Mandela Metropolitan University |
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