Synthesis Of Br(?)nsted Acidic Guanidinium Ionic Liquids And Applications In Fisher Esterification

The development of environmentally friendly catalysts,solvents for organic chemistry is one very important area of green chemistry. From the point of view of economy and enviroment , the use of clean manufacturing processes and technologies is very promising. In the last few years room temperature ionic liquids (RTILs), have been recognized as possible environmentally benign alternatives to chemical volatile solvents.The RTILs show useful properties such as thermal stability, high ionic conductivity, negligible vapor pressure and large electrochemical window. The RTILs emerged as recyclable environmentally benign reaction media for chemical processes including bio and chemical catalysis.The physical and chemical properties of RTILs, often defined as"green solvents and designer solvents",can be changed by selection of suitable cations and anions.The RTILs familiar to us are those salts with N-alkylpyridinum and N,N-dialkylimidazolium cations, such as [Bmim][PF6] (1- butyl -3-Methylimidazolium hexafluorophosphate) and [Bmim][BF4] (1- butyl-3-methylimidazolium tetrafluoroborate). At present, in order to displace toxic,harmful organic solvents and develop highly efficient green chemistry process,to develop synthesis and application of RTIL,especially, as solvents and catalysts have received much attention.There are several advantages and reasons for synthesizing alkylguanidinium-based ionic liquids: 1. The positive charge on a guanidinium cation is delocalized over one carbon and three nitrogen atoms, which gives it a high degree of thermal stability . 2 The alkyl- guanidinium salts are widely used as phase transfer catalysts due to their exceptional stability at high temperature. 3. Alkylguanidinium salts exhibit some particularities due to their extraordinary bulky cations. For example, structural features Of hexabutylguanidinium chloride , which support the existence of an electron-deficient state at the central carbon atom surrounded by the three nitrogen atoms.In this paper, we designed and synthesized a series of guanidinium halides and guanidinium ionic liquids(GRTILs) and their properties and applications were investigated .The main content is outlined as follows. Novel Br?nsted acidic ILs based on guanidinium Cations with the sulfonic acid groups have been synthesized. The ILs, as stong Br?nsted acid catalysts and solvents, shows high catalytic activity and biphsaic behavor in esterification of carboxylic acids and alcohols. The produced esters as a separate phase can be decanted conveniently out from the IL and the IL can be recyclable without any activity loss.