title: Fourier transform near-infrared vibrational circular dichroism used for on-line monitoring the epimerization of 2,2-dimethyl-1,3-dioxolane-4-methanol: A pseudo racemization reaction.
abstract: Near-infrared (near-IR) Fourier transform vibrational circular dichroism (FT-VCD) spectroscopy has been used to monitor the epimerization of (S)-(+)-2,2-dimethyl-1,3-dioxolane-4-methanol (S-DDM). The near-IR-VCD spectra display clear isolated VCD bands at the range of 4700-5050 cm(-1) resulting from the OH stretch-bend combination bands of S-DDM, which were found to decrease in intensity with increasing reaction time. The near-IR-VCD spectra of 10 reference samples obtained were subjected to partial least-squares (PLS) regression analysis, and the results were used to build predictive models for enantiomeric excess (EE) determination. Multivariate regression was carried out on three different sets of spectra, corresponding to the epimerization of S-DDM in three different solvents: methylcyclohexane, carbon tetrachloride and tetrahydrofuran. The effects of solvent in DDM epimerization are discussed in terms of the relative stabilization of the reaction intermediate of the DDM epimerization reaction. The results of these near-IR-VCD studies for the determination of EE highlights the potential of VCD for in situ real-time process monitoring of the reaction kinetics of chiral molecules in solution.
authors.affiliation: Department of Chemistry, Syracuse University, Syracuse, NY 13244, USA.
authors.forename: Changning
authors.initials: C
authors.lastname: Guo
authors.forename: Rekha D
authors.initials: RD
authors.lastname: Shah
authors.forename: John
authors.initials: J
authors.lastname: Mills
authors.forename: Rina K
authors.initials: RK
authors.lastname: Dukor
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Cao
authors.forename: Teresa B
authors.initials: TB
authors.lastname: Freedman
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Nafie
mesh_terms: D002138:Calibration; D002942:Circular Dichroism / Q000379:methods*; D004148:Dioxolanes / Q000737:chemistry*; D006860:Hydrogen Bonding; D007536:Isomerism; D015394:Molecular Structure; D009862:Online Systems; D012997:Solvents; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D014732:Vibration
chemical_list: D004148:Dioxolanes; D012997:Solvents; C024356:2,2-dimethyl-1,3-dioxolane-4-methanol