反应详情

It is known that phenol can be hydroxylated in the nucleus with aqueous hydrogen peroxide in the presence of catalytic quantities of a strong acid (DAS No. 2,064,497). The initial concentration of water in the reaction mixture, which is not regarded as critical, is less than 20% and preferably less than 10%. According to DAS No. 2,064,497, yields of around 70.3% pyrocatechol and hydroquinone, based on the hydrogen peroxide used, are obtained by using a 20-fold molar excess of the phenol, based on the quantity of peroxide, and working with hydrogen peroxide having a water content of about 5% (Example 1 of DAS No. 2,064,497). In cases where hydrogen peroxide with a water content of 56% is used (Example 4), the yield of pyrocatechol and hydroquinone is reduced to 63% under the same reaction conditions, whilst the reaction time is increased from 30 minutes to 3 hours. According to DAS No. 2,064,497, a reduction in the excess of phenol from 20 mols to 10 mols, based on 1 mol of hydrogen peroxide, reduces the yield to 60% under otherwise the same reaction conditions (Example 7 of DAS No. 2,064,497).