Study On Catalytic Performance In Organic Reactions Of N, N-dialkylimidazolium-based Ionic Liquids

Ionic liquids as the novel green materials have found wide applications in organic synthesis,catalysis chemistry,electrochemistry and material science due to their excellent properties,such as non-volatility,nonflamblity,high stability and wide electrochemical potential window and so on.However,the complex synthesis route of most ionic liquids hinders the industrial progress of them to some extend.So it becomes very important for us to explore the green and simple synthesis route and to fred new applications becomes.In this work,some novel imidazolium ionic liquids have been prepared successfully and the new applications of them in acidic catalysis and phase transfer catalysis have been found as follows.Frist,the Brφnsted acidic ionic liquid with non-volatility and low melting point had been synthesized using cheap raw material and solvent-free condition.And then the ionic liquid was applied to catalize the 2,4-diisopropyl-5,5-dimethyl-1,3-dioxane through the acetalization of TMPD and isobutyraldehyde.The results showed that acidic ionic liquid was very efficient for the reactions with the advantages of high activities,stability and reusability.The catalyst had much higher activities over the traditional homogeneous catalysis such as sulfur acid with the yield over 85%,which showed that they had great potential in the green chemical process.Second,a series of long chain ionic liquids have been synthesized and were used as phase transfer catalysts in the synthesis of N,N-diethylaniline and the oxidation of cycloheanol.A series ionic liquids with different carbon chain were used as the phase transfer catalysts to synthesize N,N-diethylaniline.The optimum reaction conditions were e ratio of aniling to bromoethane 1:2.5,the phase transfer catalyst 0.95 mol%,the reaction temperature 60℃and the reaction time 6 h under atmospheric pressure.The yield of N,N- diethylaniline reached to above 97%.The results showed that ionic liquids hols much higher activities than the traditional phase transfer catalysts.The ionic liquids were also very efficient for the oxidation of cycloheanol.The catalytic activity of sodium tungstate was improved greatly when ionic liquids were introduced in the reaction as the phase transfer catalysts.The conversion of cyclohexanol and the selectivity to cyclohexanone were about 100%and 99% respectively under optimum reaction condition(cyclohexanol 0.1 mol,30%H₂O₂ 25 mL,phase transfer catalyst 4.0 mmol,catalyst Na₂WO₄·2H₂O 5.5 mmol,90℃for 50 mins).The phase transfer catalysts had still kept the high stability of activity after reused 5 times.The results showed that both the speed of oxidation reaction and the catalytic peformance were greatly improved compared with the traditional phase transfer catalysts.