title: Effect of the solute molecular structure on its enantioresolution on cellulose tris(3,5-dimethylphenylcarbamate).
abstract: The effects of the molecular structures for 13 structurally similar chiral solutes on their HPLC retention and enantioresolutions on a commercially important polysaccharide-based chiral stationary phase, cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) are studied. Among these 13 solutes, only methyl ephedrine (MEph) shows significant enantioresolution. The retention factors of these chiral solutes vary significantly from 0.7 to 3.2 in n-hexane/2-propanol (90/10, v/v) at 298 K. The retention factors of some simpler non-chiral solutes having similar but fewer functional groups than their chiral counterparts are also studied under the same conditions and are compared to those of the chiral solutes. The H-bonding interactions between the functional groups of the solute and the C=O and NH functional groups of the polymer are probed with attenuated total reflection-infrared spectroscopy (ATR-IR) for the polymer, for binary sorbent-solute systems. The CDMPC IR amide band wavenumbers change significantly, indicating H-bonding interactions of the polymer C=O and NH groups with the solutes. The elution orders predicted for the enantiomers of these chiral solutes using molecular dynamics (MD) simulations of the polymer-solute binary systems are consistent with the HPLC results. The CDMPC cavity nano-structure and the potential interactions with chiral solutes are proposed based on HPLC data, IR data, and the simulations. The results are consistent with the three-point attachment model and support the hypothesis that significant enantioresolution requires at least three different synergistic interactions which can be a combination of steric hindrance, H-bonding, or pi-pi interactions.
authors.affiliation: School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, West Lafayette, IN 47907-2100, USA.
authors.forename: Rahul B
authors.initials: RB
authors.lastname: Kasat
authors.forename: Siao Yee
authors.initials: SY
authors.lastname: Wee
authors.forename: Ji Xian
authors.initials: JX
authors.lastname: Loh
authors.forename: Nien-Hwa Linda
authors.initials: NH
authors.lastname: Wang
authors.forename: Elias I
authors.initials: EI
authors.lastname: Franses
mesh_terms: D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D015394:Molecular Structure; D004364:Pharmaceutical Preparations / Q000302:isolation & purification*; D048448:Phenylcarbamates / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013237:Stereoisomerism
chemical_list: D004364:Pharmaceutical Preparations; D048448:Phenylcarbamates; C065943:cellulose tris-3,5-dimethylphenyl-carbamate; D002482:Cellulose