Blaz-schiemann Preparation Of Fluoro Toluene

m-Fluorotoluene is an important intermediate of medicine and fine chemical compounds. New-model antibiotic, medicine for healing high blood pressure and inflammation can be prepared from m-fluorotoluene, it is also an important intermediate for punchy soporific. There are some methods to prepare m-fluorotoluene such as Schiemann, halogen exchange, catalysis halogenation, etc..In this paper m-fluorotoluene was prepared by Schiemann reaction using m-toluidine as raw material and sodium fluoroborate as fluorinating agent. The temperature of diazotization was maintained between -5～5℃, the mole ratio of m-toluidine and hydrochloric acid was 1:2.5 and sodium nitrite was 1:1.01. Diazonium fluoroborate would be obtained by a high yield of 92.1% after anion exchange. After chloroform was found to be the best organic solvent for decomposing of diazonium and the mass ratio was 3 times than diazonium salt. The crude product m-fluorotoluene yielded to 78.3%, total yield achieve 72.1% with purity over 99%. Ethyl ether and sodium fluoride were experimented for absorbing boron fluoride and different absorbing methods were discussed. Portion of technics was optimized and some novel technics was also experimented in this paper: ( i) m-fluorotoluene and sodium nitrite were dropped simultaneously to avoid m-toluidine and hydrochlorid acid from agglomerating; (ii) sodium fluoride was utilized to absorb BF₃ recovered in the form of sodium fluoroborate that effectively improved utilization ratio of fluorine, thus cost of raw material was dropped. This technics based on Blaz-Schiemann reaction achieved certain improvement.