Study On Synthesis Procesis Of 2-bromophenol

2-Bromophenol is a kind of important industrials chemical and intermediate,mainly for the synthesis of pharmaceuticals,pesticides and other fine chemicals.It can also be used for additives of plastic and rubber,etc.Synthesis of 2-bromophenol in high selectivity reduces the cost of raw materials to lower the price of drugs,which is of vital significance.This paper researched the process routes of the 2-bromophenol,and main research work is as follows:At the first,the selectivity of 2-bromophenol in direct bromination using phenol and bromide as raw materials is low,and the the activity of phenol,2-bromophenol,4-bromophenol and 2,4-dibromophenol gradually reduce in bromo-substitution reaction.The oxy-bromination of phenol for the synthesis of 2-bromophenol,was run in the system of NaBr-H₂O₂,using acetic acid as solvent,triethylamine as addition.The conversion and selectivity of synthesis of 2-bromophenol are of 55.2%and 31.2%in the best condition.The second route for synthesis of 2-bromophenol is indirect bromination of phenol using4-tert-butylphenol as raw material,in which the conversion and yield of 2-bromo-4-tert-butylphenol are of 99.9%and 99.6%in reaction of 4-tert-butylphenol with bromine.Detail effects of reaction temperature,solvent,tert-butyl receptors,reaction time,catalyst on the tert-butyl transfer reaction for synthesis of 2-bromophenol were evaluated.Using AlCl₃ as catalyst,and phenol as solvent and tert-butyl receptors,when the molar ratio of2-bromo-4-tert-butylphenol︰aluminium trichloride︰phenol was at 1︰1︰3,the reaction conversion of 2-bromo-4-tert-butylphenol to 2-bromophenol was of 69.2%at 40℃for 5h.Using toluene as tert-butyl acceptor,trace water has an important effect on the catalytic reaction.When the reaction was run at 40℃for 5h at the molar ratio of2-bromo-4-tert-butylphenol︰AlCl₃︰H₂O being 1︰0.8︰0.13,the conversion of2-bromo-4-tert-butylphenol to 2-bromophenol reached to 96%.²⁷AlNMR analysis indicates that the activity center of catalyst may be chloroaluminium acid,which was formed from aluminium trichloride and hydrogen chloride produced by the hydrolyzation of aluminium trichloride.Further research shows that the hydrogen chloride and hydrogen bromide can increase catalytic activity of aluminium trichloride,reducing its dosage.The optimized process condition is as followed:4-tert-butylphenol reacted with bromine at 0℃in dichloromethane selectively forming 2-bromo-4-tert-butylphenol,then,aluminum trichloride and toluene were added at molar ratio of 30 and 600 at 30℃.2-bromophenol can be prepared through“one pot reaction”.The conversion and selectivity of2-bromo-4-tert-butylphenol are of 96.5%and 99.6%,respectively.