title: Insights into chromatographic enantiomeric separation of allenes on cellulose carbamate stationary phase.
abstract: Allenes are cumulenes with three contiguous carbons linked together through double bonds. 1,3-disubstituted allenes are not superimposable on their mirror image; as a consequence they are chiral. Chiral allenes are increasingly important in organic synthesis due to their interesting reactivity. Because of their applications in the field of asymmetric catalysis and in the pharmaceutical industry their optical purity is always a parameter which needs to be determined. In this article, we report the enantiomeric separation of hexa-3,4-diene-3-ylbenzene, an aromatic allene, on a cellulose carbamate (Chiralcel OD-3) stationary phase, using heptane as the mobile phase. Spectroscopic studies using infrared (IR) and vibrational circular dichroism revealed that, in the presence of heptane, the stationary phase undergoes a conformational change due to intermolecular H-bonding between the CO and NH of the neighboring polymer chains. Van't Hoff plots for the retention factor, k, showed that the retention of the two enantiomers is dominated by the enthalpy, while the plot for the selectivity, α, is entropy driven. This suggests that the enantioselectivity is a result of inclusion of the enantiomers in the cavities of the chrial stationary phase. VCD spectra, along with density functional theory calculation (DFT) of the interaction between each enantiomer and the chiral stationary phase, supported the chromatographic elution order findings.
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA.
authors.forename: Shengli
authors.initials: S
authors.lastname: Ma
authors.affiliation: Purdue University, School of Chemical Engineering, West Lafayette, IN 47907-2100, USA.
authors.forename: Hung-Wei
authors.initials: HW
authors.lastname: Tsui
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA.
authors.forename: Earl
authors.initials: E
authors.lastname: Spinelli
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA.
authors.forename: Carl A
authors.initials: CA
authors.lastname: Bussaca
authors.affiliation: Purdue University, School of Chemical Engineering, West Lafayette, IN 47907-2100, USA.
authors.forename: Elias I
authors.initials: EI
authors.lastname: Franses
authors.affiliation: Purdue University, School of Chemical Engineering, West Lafayette, IN 47907-2100, USA.
authors.forename: Nien-Hwa Linda
authors.initials: NH
authors.lastname: Wang
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Wu
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA.
authors.forename: Heewon
authors.initials: H
authors.lastname: Lee
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Senanayake
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Yee
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA.
authors.forename: Nina
authors.initials: N
authors.lastname: Gonnella
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA.
authors.forename: Keith
authors.initials: K
authors.lastname: Fandrick
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd, Ridgefield, CT 0677-0368, USA. Electronic address: nelu.grinberg@boehringer-ingelheim.com.
authors.forename: Nelu
authors.initials: N
authors.lastname: Grinberg
mesh_terms: D000466:Alkadienes / Q000737:chemistry / Q000302:isolation & purification*; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D002942:Circular Dichroism; D048448:Phenylcarbamates / Q000737:chemistry*; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D000466:Alkadienes; D048448:Phenylcarbamates; C065943:cellulose tris-3,5-dimethylphenyl-carbamate; C025947:propadiene; D002482:Cellulose
keywords: Allene; Infrared spectroscopy; Molecular modeling; Thermodynamics; Vibrational circular dichroism