Electrophilic substitution with rearrangement. Part 8. Some products of bromination of 3,4-dimethylphenol; a route to substitution meta- to a hydroxy-group
The brominations of 3,4-dimethylphenol, 2- or 6-bromo-3,4-dimethylphenol, and 2,6-dibromo-3,4-dimethylphenol can lead under defined conditions either to 2,5,6-tribromo-3,4-dimethylphenol or to 2,4,6-tribromo-3,4-dimethyl-cyclohexa-2,5-dienone. The latter compound rearranges to give the former when it is dissolved in concentrated sulphuric acid; and to give 2,6-dibromo-4-bromomethyl-3-methylphenol when it is set aside in the light at room temperature. When 2,5,6-tribromo-3,4-dimethylphenol is heated with concentrated aqueous hydrogen iodide, 5-bromo-3,4-dimethylphenol is obtained; this with bromine gives a mixture of 2,5- and 5,6-dibromo-3,4-di-methylphenol. The mechanisms of these reactions are outlined.