Cellulose Benzoates For Efficient Separation Of Enantiomers:Synthesis And Properties

The cellulose benzoates and mixed acid esters have very good chiral recognition ability, so they are widely used as chiral separation materials. But the precise and controllable preparation is difficult to realize, which limits the development of this kind of materials. Development of new type of controllable preparation methods, precise design and synthesis of cellulose chiral separation materials of specific structure has important academic significance and good application prospect. The appearent of ionic liquids(ILs) in recent years, which provides a new way for homogeneous controllable preparation of cellulose derivatives. This paper studied the regularity and mechanism of the reaction between cellulose and a variety of sterically replacing benzoyl in detail, by ionic liquid as the medium, under the condition of pyridine as catalyst, developed a new method to prepare chiral separation materials of cellulose ester. Thus we precisely design and compoud a variety of chiral stationary phase of cellulose ester of clear structure, preliminarily reveals the relationship between structure and chiral separation performance.1. Homogeneous benzoylation of polysacchrides in1-Allyl-3-methylimidazolium Chloride(AmimCl): Homogeneous benzoylation of cellulose was investigated systematically with eight kinds of substituted benzoyl chloride in AmimCl. Combing Hammett plot, it reveals the reaction mechanism of cellulose and benzoyl chloride: Under the condition of presence of pyridine, benzoylation of cellulose in the AmimCl is nucleophilic addition first of all, forming tetrahedral intermediate, then removing a negative ion pairs of molecules.2. Furthermore, NMR measurement of cellulose benzotes demonstrated that most of benzoyl chlorides show relatively high regioselectivity at the C-6position of cellulose in AmimCl and the high regioselectivity of cellulose benzoylation was attributed to the synergistic effect of appropriate reaction rate,moderate steric effect and reaction mechanism. In pyridine as catalyst, the selective reduced.3. Preparation of coating cellulose benzoates as chiral stationary phase:according to the rules and reaction mechanism, a variety of cellulose benzoates and mixed acid ester was prepared, they ware loaded on the silica gel by depositing method in order to obtain coated chiral stationary phase of cellulose derivatives. The chiral separation performance was investigated, and the relation between cellulose benzoate structure and chiral separation performance was revealed:(1) The substitution degree of cellulose benzoates have effects on chirality separation effect. The same kind of chiral stationary phase, The bigger of the substitution degree of cellulose benzoates, the results of chiral resolution is better.(2) The different position of the substituent on the benzene ring,cellulose benzoate have different chiral separation effects on different drugs. For some chiral drugs, the para orientation on the benzene ring of cellulose benzoic acid esters derivatives has a better chiral separation effect than any other position.(3) The benzene ring of cellulose benzoic acid esters derivatives connected electron donating substituent group has a better chiral separation effect than connected electron-withdrawing substituent group.(4)Different proportion of mobile phase, the chiral separation effect of cellulose benzoate will also be different.