Research On The Isomerization Of Liquid Crystal Compounds Containing Cyclohexane

Liquid crystal compounds containing cyclohexane structure has lower viscosity,lower melting point,wide temperature range of nematic phase and higher clearing point,and has been widely used in the field of liquid crystal materials.However,there can be a relatively high concentration of cis configuration in the process of the compound synthesis due to the special three-dimensional structure of cyclohexane.Because direct separation of cis configuration would sacrifice the utilization rate of raw materials,it is of great significance to choose appropriate catalyst which could translate cis configuration into trans configuration.In order to comply with the needs of practical production,we selected the conventional synthesis methods in the industry to synthesize the target products A and B;and catalyzed the isomerization reaction of the compounds using different catalysts,as well as compared the different between the reactions and explored the best technology.Finally,the compounds were characterized through methods such as the infrared absorption and gas chromatograph.First of all,we used propyldicyclohexylanone and bromoethylbenzene as raw materials to synthesize compound A through grignard reaction,dehydration reaction and catalytic hydrogenation;used 2,3-difluoroanisole and 4-propylcyclohexanone to synthesize the compound B through lithiation reaction,dehydration reaction and catalytic hydrogenation.Then different catalysts were selected to conduct the isomerization reaction.The optimum technological condition of catalyzing compound A using AlCl₃ as a lewis acid catalyst is: utilizing 1:0.15 as the molar ratio between A and AlCl₃,an optimum reaction temperature of-30 ℃ and a reaction time of 60 min with dichloromethane as the solvent.The optimum technological condition of catalyzing compound B using AlCl₃ as lewis acid catalyst is: utilizing 1:1.4 as the molar ratio between compound B and AlCl₃,an oprimum reaction temperature of-10℃ and a reaction time of 4 h with dichloromethane as solvent.The optimum technological condition of catalyzing compound A using CF₃SO₃ H as proton acid catalyst is: utilizing 1:0.3 as the molar ratio between compound A and CF₃SO₃ H,an optimum reaction temperature of-30℃and a reaction time of 2 h with dichloromethane as the solvent.