Synthesis And Properties Of Chiral Guanidinium & Guanidinium Ionic Liquids

Room temperature ionic liquids (RTILs) consist of relative bulky structure of organic cation and relative small structure of inorganic anion, as well as it is liquid at room temperature. The Room Temperature Ionic Liquids (RTILs) show useful properties such as thermal stability, insipid, nonflammable, high ionic conductivity, negligible vapor pressure and large electrochemical window, circular. The physical and chemical properties of RTILs, often defined as"green solvents and designer solvents", can indeed varied over a wide range by selection of suitable cations and anions.Chiral ionic liquids are functionalized ionic liquids which are designed for being satisfied to have specific functional requirement, including the functionalized in physical property such as flow property, conduct ability and range of liquid, also in chemical property such as polarity, acidity, chirality, ligand function, solubility. Now, it is hot that grafting varies of functional groups into chiral ionic liquids and then bringing about functionalized ionic liquids which are assigned for being satisfied to have specific requirement. That is important aspect in studying functionalized ionic liquids. Because of having merits of ionic liquids and chirality, chiral ionic liquid can apply in the aspect of asymmetry synthesis, chiral isolating and chiral catalysis as chiral solvent or chiral induction solvent.Recently, more and more people focus on researching chiral ionic liquid as chiral solvent. That is because it has many perfect properties as follows. First, chiral ionic liquids are synthesized readily. Its chirality derives from a large of chiral chemical solvent such as chiral amine, chiral halogen compounds and alcohol, also from the natural and cheap products existing in nature such as natural amino acid, hydroxyl acid and alcohol. There is a big assigned space for the parts of anion ion and cation ion. Meanwhile, through assigning the chiral axis and chiral plane we also got chiral ionic liquids which have not chiral center.Secondly: The"task-specific"or"tailor-making"chiral ionic liquids. CILs belongs to the fields of functionalized ionic liquid. The concept of tailor–made chiral solvents is rather new and could afford novel molecular structures and materials, as well as new insights for chiral recognition and materiality transfers.Thirdly:The specific properties of chiral ionic liquids (CILs) .Except for the better properties of classical ionic liquids ,such as thermal stability; insipid; nonflammable; high ionic conductivity; negligible vapor pressure and large electrochemical window; circular, the chirality is the point of chiral ionic liquids. It has been reported that most of the ionic liquids possess a polymeric behavior and are highly ordered H-bonded liquids (three–dimensional networks of anions and cations linked together by hydrogen bonds).These specific properties suggest that chiral ionic liquids could outperform the classical chiral solvents for asymmetric induction.There are several advantages and reasons for synthesizing alkylguanidinium- based ionic liquids: a. the positive charge in the guanidinium is delocalized over one carbon and three nitrogen atoms, which gives them a high degree of thermal stability compared to tetraalkylammonium salts. b. The alkyl-guanidinium halides are widely used as phase transfer catalyst due to their exceptional stability at high temperature. c. Alkylguanidinium exhibits some particularities due to its extraordinary bulkiness. For example, the literature reports structural features, which support the existence of an electron-deficient state at the central carbon atom surrounde by the three nitrogen atoms.In this paper, we designed and synthesized a series of chiral guanidinium halides and chiral guanidinium ionic liquids(CGRTILs) deriving from a series of natural amino acid,and studied their properties and applications. The main content is outlined as following:1. Chiral guanidinium halides were synthesized with the materials of natural amino acid. At first, a series of L-amino ester hydrochloride were prepared through the SOCl2's method and got better yield. After that the"Vilsmeier salts"were synthesized from oxalyl chloride and 1,3-dimethyl-2-imidazolidinone ,then reacted with amino acid ethyl ester hydrochloride in dichloromethane. At last the chiral hexaalkyl guanidinium halide (GX) was synthesized from exchanging with iodomethane .2. Chiral guanidinium ionic liquids were synthesized by ionic exchange. We studied in full the physic-chemical properties of a number of CGRILs, involving thermal stability and solubility. The results as following: TGA indicated that the ionic liquids with tetrafluoroborate are stable to at least 200oC and with hexafluorophosphate are stable to at least 300oC. From the data which are determined, we found that the CGRTILs exhibit more wide and more stable range of liquids. From the table we also discovered that chiral ionic liquids are readily soluble in most organic solvents. Tetrafluoroborate have good solubility in water, whereas the hexafluorophosphate.