Synthesis of 4-(trans-4-n-propylcyclohexyl)-fluorobenzene for monomer of liquid crystal

A new method of synthesis of 4- (trans-4-n-propylcyclohexyl)-fluorobenzene was described. Two steps that the production of 4-( 4-propionylcyclohexyl) -fluorobenzene and its reduction were involved in this method. The first step, a mixture of cyclohexene and propionyl chloride was added dropwise to a suspension of aluminum chloride in (fluorobenzene) with stirring and cooling to -10 ℃. The mol ratio of cyclohexene, propionyl chloride, (aluminum )chloride and fluorobenzene was 1∶1∶1.5∶2. The reaction mixture was stirred subsequently at 40 ℃ for 2 h and the 4-(4-propionylcyclohexyl)-fluorobenzene was gotten. The second step, the 4-(4-propionylcyclohexyl)-fluorobenzene was reduced to 4-( trans-4-n-propylcyclohexyl ) -fluorobenzene by HuangMinglong reduction, which was distilled under reduced (pressure) (0.67—1.33 kPa) and recrystallized several times from ethanol. The pure compound was gotten and the purity was higher than 99.5%.