The Sutdy Of Electrooxidation Of Phenols And Acid Catalytic Synthesis Of P-hydroxyanisole

Quinone compounds,phenol bromide derivatives,p-hydroxyanisole and other phenol ether compounds are important organic chemical raw materials,widely used in medicine,pesticides and dyes.The main research contents of this paper are:electrochemical oxidation of phenolic compounds such as phenol and hydroquinone to synthesize corresponding quinone compounds;electrochemical oxidative bromination of phenols such as phenol,p-tert-butylphenol and p-cresol to synthesize bromine of corresponding phenols substituted derivatives;p-hydroxyanisole and other phenol ether compounds were synthesized from quinhydrone.?1?Synthesis of p-benzoquinone by electrochemical oxidation of phenol and hydroquinone respectively,phenol conversion rate is 20.62%,p-benzoquinone selectivity is 100%;hydroquinone conversion rate is greater than 99%,and the yield of p-benzoquinone is 98%.The synthesis of1,4-naphthoquinone by electrooxidation of 1-naphthol gave a selectivity of1,4-naphthoquinone of 100%and a yield of 27.39%.Electrooxidation of hydroquinone to synthesize quinhydrone,preferred conditions:200 mL 5%sulfuric acid solution,15 g hydroquinone,constant temperature 30°C,current2 A,energization time 110 min.Five times of parallel amplification confirmed that the average yield of quinhydrone was greater than 86%.?2?The electrochemical bromination reaction conditions are mild,the bromine atom utilization rate is close to 100%,and the yields of the products obtained by electrooxidation bromination are:18.55%for p-bromophenol and2,4,6-tribromophenol for 93.76%,2,6-dibromo-p-cresol is 94.15%,except for p-bromophenol,other bromo derivatives of phenol get higher yield.More specifically,4-methoxyphenol is not brominated but is oxidized to form p-benzoquinone.?3?Optimized conditions for the synthesis of p-hydroxyanisole:quinhydrone 1 g?4.58 mmo1?,0.1 g?0.0174 mmo1?phosphotungstic acid,10mL anhydrous methanol,and reacted at 70°C for 4 h.Gas chromatography?GC?analysis showed that the conversion of quinhydrone was 97.11%,the selectivity to p-hydroxyanisole was 98.33%,and the yield was 95.49%.Using a phosphotungstic acid as a catalyst,other phenol ethers were synthesized by expansion of different alcohol substrates,wherein the yield of 4-ethoxyphenol was 92.45%,and the yield of 4-n-octyloxyphenol was 92.35%.The yield of most other products was greater than 90%except that the yield of4-tert-butoxyphenol,4-tert-pentyloxyphenol and 4-trifluoroethoxyphenol was0%.The synthesis of p-hydroxyanisole using 732 strong acid cation exchange resin as a catalyst also achieved good results with a yield of about 90%.Finally,the mechanism of etherification reaction was discussed and improved.The above products were detected by means of GC,FT-IR,¹H NMR and¹³C NMR.