Hydrobromic Acid / Hydrogen Peroxide Bromination System Applications And 4 - Methyl Benzophenone Derivatives

Recently,a new bromination method was mentioned—HBr/H₂O₂ bromination method,which not only can overcome some defects of NBS/BPO and Br₂/inititior bromination methods,such as low conversion, dangerous operation,corrosive reagents,complicated work-up and so on, but also has its advantages,including high efficient,safe and simple.And 4-bromomethylbenzophenone is an important chemical intermediate, which often is prepared by NBS/BPO or Br₂/inititior methods bromizing 4-methylbenzophenone.Thus,in this paper,we chose HBr/H₂O₂/light method to investigate the benyl free radical bromination of 4-methylbenzophenone and optimized the reaction conditions.At the same time,in order to comparing with the method,the NBS/BPO and Br₂/inititior methods also had been used brominated the 4-methylbenzophenone.The results showed that the HBr/H₂O₂/light bromination method could obtain 95%conversion,but NBS/BPO and Br₂/inititior bromination methods just got 67.8%and 78.3%conversion, respectively.According the experiment result above and as HBr/H₂O₂ method never being used in allyl bromination,we studied some olefins brominating with the HBr/H₂O₂/light method in order to obtain allyl bromide,and the cyclohexene was chosen as the model substrate to study the reaction,but the experiment results indicated that the main product was 2-bromocyclohex-1-ol with some 1,2-dibromocyclohexane, and the main product was 3-bromocyclohexene with a small mount of 1,2-dibromocyclohexane with NBS/BPO method.With the optimum conditions,some olefins were carried out the bromination under HBr/H₂O₂/light condition.Although the first purpose we hope the allylic bromination of alkenes could happen,in fact,the results suggested that the main products were bromohydrins with little dibromo-products.Of course,it was a good method for gaining bromohydrins,which often were synthetized by metal salt reagent catalysis.As benzophenone derivatives,which have good photochemistry properties,are commonly applied in the area of photoinitiators, Ultra-violet absorbers,electronic and medicinal industry and so on,we also synthesed some benzophenone derivatives by carrying out the hydrolysis and aminolysis of 4-bromomethylbenzophenone.In the hydrolysis experiment of 4-bromomethylbenzophenone,the influence of the mount of alkali was been studied,which showed that the reaction time prolonged with the decreasing of alkali amount among 4eq.to 2eq.;when reducing to 1.1eq.,the conversion decreased as well. 4-Chloromethylbenzophenone was undergone to the hydrolysis,but it needed much longer reaction time with somewhat low conversion.The effects of the solvent and temperature were explored in the aminolysis reaction of 4-bromomethylbenzophenone with ethanolamine,and it showed the room temperature was better for the reaction;in the aminolysis reaction of 4-chloromethylbenzophenone with ethanolamine, bad conversion and long reaction time had occurred,even if a little of KI as the catalysis was added.At last,we tested the UV curing performance with some compounds. The results showed that the di(4-benzoylbenzyl)aether was not fit to as the photoinintitor for becoming yellow in preparing coating solvent,and others displayed fine effect.