The Studies Of The Dealkylation Of 2,5-di-tert-butylhydroquinone And Synthesis Of Derivatives Of Phenol By The Site Occupation Of Tertiary Butyl Regiment

The Friedel-Crafts reaction is one of the common organic synthesis reactions. It has beed widely applied in petroleum chemical industry, fine chemicals chemistry, perfumery compounds and spices, etc. The alkylation reaction via Friedel-Crafts process will be reversible. Dealkylation, alkyl convertion or carbon chain broken will occur under violence conditions such as strong catalyst, high temperature, long reaction time and so on.The dealkylation reactions of 2,5-di-tert-butylhydroquinone(DTBHQ) in xylene and water have been studied. We have discussed the effects of different catalysts, the amounts of catalyst, reaction times, and the amounts of water on dealkylation of DTBHQ in xylene. The good result was that the selectivity of 2-tert-butylhydroquinone(TBHQ) was 74.0% with DTBHQ conversion of 43.1% and TBHQ yield of 31.9%, when 20g of DTHBQ was refluxed in 100ml of xylene for 2 hours catalyzed by 1.5g of phosphotungstic acid. The results of reaction became poor by adding water in the reaction. The reason could be that phosphotungstic acid with crystal water would become less dissolving in reaction mixture by adding more water. The anhydrous phosphotungstic acid catalyzed a poor reaction because its catalytic activity could be strengthened, while the selectivity weakened by improved acidity through losing water.We have also discussed the effects of different catalysts, the amounts of catalyst, reaction temperatures, and the amounts of redutants on dealkylation of DTBHQ. The good result was that the selectivity of TBHQ was 34.68% with DTBHQ conversion of 32.3% and TBHQ yield of 11.2%, when 40g of DTHBQ was heated in 200ml of water at 220℃ for 2 hours catalyzed by 10g of acetic acid. It can be drawn from the experimental results that the catalytic activity is higher when the acidity of catalyst is stronger. So the dealkylation of DTBHQ proceeds completely, while the selectivity of dealkylation is poor. The catalysts of weak acid, which catalyzed no reaction in xylene, could catalyze dealkylation in water. Although the catalytic activity of weak acids was poor, their selectivity was relatively high. It shows the dealkylation was more easier in the water than that in the xylene. It has somesignificance that the reaction proceed in solvent water under high temperature and high pressure from the point of green chemistry.As a site occupation group, besides sulfonic group, other groups such as tertiary butyl have beed studied less. Here we have tried to synthesize phenol compounds through site occupation by tert-butyl. First, the o- or p-positions of resorcin and phenol were occupied by tert-butyl through Friedel-Crafts alkylation. Then, the nitro-group and bromid were bonded to o-position of hydroxyl. Finally, 2, 6-dinitrophenol, 2-bromophenol and 2-bromoresorcin were prepared by dealkylation of tert-butyl, and confirmed by IR , GC-MS and measurement of melting point compared with the values of the literatures. The yields of 2, 6-dinitrophenol, 2-bromophenol and 2-bromoresorcin were 24.5%, 32.5%, 32.7% respectively based on 4-tert-butylphenol and 4,6-di-tert-butylresorcinol. The results show that synthesis of some compounds through the site occupation of tertiary butyl group could be worked.