Synthesis And Application Of Urea-based Symmetric Cation Liquids

Functionalized symmetric dicationic ionic liquids are composed of two pairs of same anions and cations.The cations are connected by symmetrical spacers,and functional groups could be introduced into the same position of the spacers,anions or cations.Compared to traditional monocationic ionic liquids,they have been improved on physicochemical properties as well as application prospects.These ionic liquids could be further improved on designability and more pertinent on applicability because of the introduction of different functional groups.Therefore,it is valuable to carry out the development and application potentiality of functionalized symmetric dicationic ionic liquids.According to the two-step synthesis method,different nitrogen containing heterocyclic compounds were chosen as substrates and reacted with diverse spacers.These corresponding halides were firstly synthesized by quaternization reaction,and then gone through different anion exchange reactions to obtain all dicationic ionic liquids.4 Kinds functionalized symmetric dicationic ionic liquids including 27 compounds were finally synthesized.Wherein,ureido-based imidazolium type ionic liquids were originally reported.Esterification reaction and degradation of biomass were selected as template reactions to explore the catalytic activity of these ionic liquids.Primarily,a green and efficient protocol was developed for the degradation of biomass.By comparing the catalytic efficiency of different imidazolium type ionic liquids,the best one was determined.Different carbohydrates were successfully converted into 5-hydroxy-methylfurfural(HMF)using symmetric ureido-functionalized dicationic ionic liquid with p-toluenesulfonic acid anions as dual catalyst-solvent under microwave irradiation.The optimum reaction system was determined by screening the influencing factors such as microwave wattage,substrate concentration,reaction time,etc.And the carbohydrates could be converted into 5-hydroxymethylfurfural(HMF)and further etherified into 5-ethoxymethylfurfural(EMF)with the addition of ethanol.Itwas found that the optimal catalytic system had high catalytic efficiency,easy operation and after-treatment.Besides,the optimal protocol could be recycled five times.Following,a new system was developed for the esterification of carboxylic acid with primary chlorinated hydrocarbons in ethanol aqueous solution using DBU-based dicationic ionic liquid as catalyst.The corresponding optimum reaction conditions were obtained by investigating different reaction conditions such as type and dosage of catalyst,solvent,reaction temperature and so on.Twenty esterification products were successfully synthesized under the optimum conditions.Meanwhile,the product was easy to separate and the catalyst had good stability and activity.