1
|
Chiral Discrimination Mechanisms by Silylated-Acetylated Cyclodextrins: Superficial Interactions vs. Inclusion. Int J Mol Sci 2022; 23:ijms232113169. [DOI: 10.3390/ijms232113169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/13/2022] [Accepted: 10/26/2022] [Indexed: 11/16/2022] Open
Abstract
Cyclodextrin derivatives constitute a powerful class of auxiliary agents for the discrimination of apolar chiral substrates. Both host–guest inclusion phenomena and interactions with the derivatizing groups located on the surface of the macrocycle could drive the enantiodiscrimination; thus, it is important to understand the role that these processes play in the rational design of new chiral selectors. The purpose of this study is to compare via nuclear magnetic resonance (NMR) spectroscopy the efficiency of silylated-acetylated α-, β-, and γ-cyclodextrins in the chiral discrimination of 1,1,1,3,3-pentafluoro-2-(fluoromethoxy)-3-methoxypropane (compound B) and methyl 2-chloropropionate (MCP). NMR DOSY (Diffusion Ordered SpectroscopY) experiments were conducted for the determination of the bound molar fractions and the association constants, whereas ROESY (Rotating-frame Overhauser Enhancement SpectroscopY) measurements provided information on the hosts’ conformation and on the interaction phenomena with the guests. Compound B, endowed with fluorinated moieties, is not deeply included due to attractive Si-F interactions occurring at the external surface of the cyclodextrins. Therefore, a low selectivity toward the size of cyclodextrin cavity is found. By contrast, enantiodiscrimination of MCP relies on the optimal fitting between the size of the guest and that of the cyclodextrin cavity.
Collapse
|
2
|
Eor P, Anderson JL. Using a Chromatographic Pseudophase Model To Elucidate the Mechanism of Olefin Separation by Silver(I) Ions in Ionic Liquids. Anal Chem 2021; 93:13284-13292. [PMID: 34549946 DOI: 10.1021/acs.analchem.1c02885] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Silver(I) ions undergo selective olefin complexation and have been utilized in various olefin/paraffin separation techniques such as argentation chromatography and facilitated transport membranes. Ionic liquids (ILs) are solvents known for their low vapor pressure, high thermal stability, low melting points, and ability to promote a favorable solvation environment for silver(I) ion-olefin interactions. To develop highly selective separation systems, a fundamental understanding of analyte partitioning to the stationary phase and the thermodynamic driving forces behind solvation is required. In this study, a chromatographic model treating silver(I) ions as a pseudophase is constructed and employed for the first time to investigate the olefin separation mechanism in silver(I) salt/IL mixtures. Stationary phases containing varying amounts of noncoordinated silver(I) salt ([Ag+][NTf2-]) dissolved in the 1-decyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C10MIM+][NTf2-]) IL are utilized to determine the partition coefficients of various analytes including alkanes, alkenes, alkynes, aromatics, aldehyde, esters, and ketones. As ligand coordination to silver(I) ions is known to lower its olefin complexation capability, this study also examines two different types of coordinated silver(I) ion pseudophases, namely, monocoordinated silver(I) salt ([Ag+(1-decyl-2-methylimidazole, DMIM)][NTf2-]) and dicoordinated silver(I) salt ([Ag+(1-methylimidazole, MIM)(DMIM)][NTf2-]). The extent of olefin partitioning to the coordinated silver(I) ion pseudophases over the carrier gas and IL decreased by up to two orders of magnitude. Values for enthalpy, entropy, and free energy of solvation were determined for the three silver(I) ion-containing systems. Olefin retention was observed to be enthalpically dominated, while ligand coordination to the silver(I) ion pseudophase resulted in variations for both enthalpic and entropic contributions to the free energy of solvation. The developed model can be used to study chemical changes that occur in silver(I) ions over time as well as identify optimal silver(I) salt/IL mixtures that yield high olefin selectivity.
Collapse
Affiliation(s)
- Philip Eor
- Ames Laboratory-USDOE, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, Iowa 50011, United States
| | - Jared L Anderson
- Ames Laboratory-USDOE, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, Iowa 50011, United States
| |
Collapse
|
3
|
Mandoli A, Schurig V. Separation of Enantiomers by Inclusion Gas Chromatography: On the Influence of Water in the Molecular Complexation of Methyl 2-Chloropropanoate Enantiomers and the Modified γ-Cyclodextrin Lipodex-E. Chirality 2015; 28:124-31. [PMID: 26636659 DOI: 10.1002/chir.22557] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 09/28/2015] [Accepted: 11/02/2015] [Indexed: 11/09/2022]
Abstract
A profound influence of water has previously been detected in the complexation of the enantiomers of methyl 2-chloropropanoate (MCP) and the chiral selector octakis(3-O-butanoyl-2,6-di-O-pentyl)-γ-cyclodextrin (Lipodex-E) in NMR and sensor experiments. We therefore investigated the retention behavior of MCP enantiomers on Lipodex-E by gas chromatography (GC) under hydrous conditions. Addition of water to the N2 carrier gas modestly reduced the retention factors k of the enantiomers, notably for the second eluted enantiomer (S)-MCP. This resulted in an overall decrease of enantioselectivity -ΔS,R (ΔG) in the presence of water. The effect was fully reversible. Consequently, for a conditioned column in the absence of residual water, the determined thermodynamic data, i.e. ΔS,R (ΔH) = -12.64 ± 0.08 kJ mol(-1) and ΔS,R (ΔS) = -28.18 ± 0.23 J K(-1) mol(-1), refer to a true 1:1 complexation process devoid of hydrophobic hydration.
Collapse
Affiliation(s)
- Alessandro Mandoli
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Pisa, Italy
| | - Volker Schurig
- Institut für Organische Chemie, Universität Tübingen, Tübingen, Germany
| |
Collapse
|
4
|
Uccello-Barretta G, Schurig V, Balzano F, Vanni L, Aiello F, Mori M, Ghirga F. Synergistic Effects of Trace Amounts of Water in the Enantiodiscrimination Processes by Lipodex E: A Spectroscopic and Computational Investigation. Chirality 2014; 27:95-103. [DOI: 10.1002/chir.22394] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 08/29/2014] [Accepted: 09/03/2014] [Indexed: 11/10/2022]
Affiliation(s)
| | - Volker Schurig
- Institute of Organic Chemistry; University of Tübingen; Tübingen Germany
| | - Federica Balzano
- Department of Chemistry and Industrial Chemistry; University of Pisa; Pisa Italy
| | - Letizia Vanni
- Department of Chemistry and Industrial Chemistry; University of Pisa; Pisa Italy
| | - Federica Aiello
- Department of Chemistry and Industrial Chemistry; University of Pisa; Pisa Italy
| | - Mattia Mori
- Center for Life Nano Science@Sapienza; Istituto Italiano di Tecnologia; Rome Italy
| | - Francesca Ghirga
- Department of Chemistry and Drug Technology; Sapienza University; Rome Italy
| |
Collapse
|
5
|
Lebed PJ, Keunchkarian S, Osorio Grisales J, Castells CB. Measurements of association constants between enantiomers and chiral selectors by capillary gas chromatography. Theoretical and practical considerations. J Chromatogr A 2014; 1324:198-206. [DOI: 10.1016/j.chroma.2013.11.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 11/04/2013] [Accepted: 11/05/2013] [Indexed: 11/29/2022]
|
6
|
Enantiomeric separation of volatile organics by gas chromatography for the in situ analysis of extraterrestrial materials: kinetics and thermodynamics investigation of various chiral stationary phases. J Chromatogr A 2013; 1306:59-71. [PMID: 23921265 DOI: 10.1016/j.chroma.2013.07.058] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 07/13/2013] [Accepted: 07/15/2013] [Indexed: 11/20/2022]
Abstract
The performances of several commercial chiral capillary columns have been evaluated with the aim of determining the one most suitable for enantiomeric separation in a gas chromatograph onboard a space probe. We compared the GC-MS response of three capillary columns coated with different chiral stationary phases (CSP) using volatile chiral organic molecules which are potential markers of a prebiotic organic chemistry. The three different chiral capillary columns are Chirasil-Val, with an amino acid derivative CSP, ChiralDex-β-PM, with a CSP composed of dissolved permethylated β-cyclodextrins in polysiloxane, and Chirasil-Dex, with a CSP made of modified cyclodextrins chemically bonded to the polysiloxane backbone. Both kinetics and thermodynamics studies have been carried out to evaluate the chiral recognition potential in these different types of columns. The thermodynamic parameters also allow a better understanding of the driving forces affecting the retention and separation of the enantiomers. The Chirasil-Dex-CSP displays the best characteristics for an optimal resolution of the chiral compounds, without preliminary derivatization. This CSP had been chosen to be the only chiral column in the Sample Analysis at Mars (SAM) experiment onboard the current Mars Science Laboratory (MSL) mission, and is also part of the Mars Organic Molecules Analyzer (MOMA) gas chromatograph onboard the next Martian mission ExoMars. The use of this column could also be extended to all space missions aimed at studying chirality in space.
Collapse
|
7
|
Schurig V. Salient Features of Enantioselective Gas Chromatography: The Enantiomeric Differentiation of Chiral Inhalation Anesthetics as a Representative Methodological Case in Point. Top Curr Chem (Cham) 2013; 340:153-207. [DOI: 10.1007/128_2013_440] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
|
8
|
A practical method for the quantitative assessment of non-enantioselective versus enantioselective interactions encountered in liquid chromatography on brush-type chiral stationary phase. J Chromatogr A 2012; 1269:270-8. [DOI: 10.1016/j.chroma.2012.10.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 10/01/2012] [Accepted: 10/02/2012] [Indexed: 11/20/2022]
|
9
|
Zhan F, Yu G, Yao B, Guo X, Liang T, Yu M, Zeng Q, Weng W. Solvent effect in the chromatographic enantioseparation of 1,1′-bi-2-naphthol on a polysaccharide-based chiral stationary phase. J Chromatogr A 2010; 1217:4278-84. [DOI: 10.1016/j.chroma.2010.04.016] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 04/03/2010] [Accepted: 04/09/2010] [Indexed: 11/25/2022]
|
10
|
Use of derivatized cyclodextrins as chiral selectors for the separation of enantiomers by gas chromatography. ANNALES PHARMACEUTIQUES FRANÇAISES 2010; 68:82-98. [DOI: 10.1016/j.pharma.2009.11.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 11/24/2009] [Accepted: 11/26/2009] [Indexed: 11/18/2022]
|
11
|
Sicoli G, Kreidler D, Czesla H, Hopf H, Schurig V. Gas chromatographic enantioseparation of unfunctionalized chiral alkanes: A challenge in separation science (overview, state of the art, and perspectives). Chirality 2009; 21:183-98. [DOI: 10.1002/chir.20638] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
12
|
Schurig V. Elaborate treatment of retention in chemoselective chromatography--the retention increment approach and non-linear effects. J Chromatogr A 2008; 1216:1723-36. [PMID: 19070865 DOI: 10.1016/j.chroma.2008.11.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 11/07/2008] [Accepted: 11/10/2008] [Indexed: 11/27/2022]
Abstract
The retention increment approach is described which quantifies the association equilibria of a selectand and a selector in complexation and inclusion chromatography. A thermodynamic treatment of enantioselectivity based on retention phenomena in chromatography including entropy/enthalpy compensation and the isoenantioselective temperature is advanced. Kinetic parameters of enantiomerization are discussed. Non-linear effects, both existent and elusive, are described and proposed, respectively. The enantioselectivity pertaining to catalysis vs. chromatography is compared and a unified nomenclature is proposed. Through an educational effort, this account is aimed at providing a deeper insight into chemoselective aspects of chromatography thereby stimulating further research of both established and speculative phenomena of the most intriguing manifestation of chemoselectivity, that is, of enantioselectivity.
Collapse
Affiliation(s)
- Volker Schurig
- Institute of Organic Chemistry, University of Tübingen, 72076 Tübingen, Germany.
| |
Collapse
|
13
|
Weng W, Guo H, Zhan F, Fang H, Wang Q, Yao B, Li S. Chromatographic enantioseparations of binaphthyl compounds on an immobilized polysaccharide-based chiral stationary phase. J Chromatogr A 2008; 1210:178-84. [DOI: 10.1016/j.chroma.2008.09.048] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 09/14/2008] [Accepted: 09/15/2008] [Indexed: 11/28/2022]
|
14
|
A Maltooctaose Derivative (“Acyclodextrin”) as a Chiral Stationary Phase for Enantioselective Gas Chromatography. European J Org Chem 2008. [DOI: 10.1002/ejoc.200800508] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
15
|
Poole CF, Poole SK. Separation characteristics of wall-coated open-tubular columns for gas chromatography. J Chromatogr A 2008; 1184:254-80. [PMID: 17678934 DOI: 10.1016/j.chroma.2007.07.028] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Revised: 07/01/2007] [Accepted: 07/13/2007] [Indexed: 10/23/2022]
Abstract
The application of the solvation parameter model for the classification of wall-coated open-tubular columns for gas chromatography is reviewed. A system constants database for 50 wall-coated open-tubular columns at five equally spaced temperatures between 60 and 140 degrees C is constructed and statistical and chemometric techniques used to identify stationary phases with equivalent selectivity, the effect of monomer chemistry on selectivity, and the selection of stationary phases for method development. The system constants database contains examples of virtually all commercially available common stationary phases.
Collapse
Affiliation(s)
- Colin F Poole
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA.
| | | |
Collapse
|
16
|
Levkin PA, Schurig V. Apparent and true enantioselectivity of single- and binary-selector chiral stationary phases in gas chromatography. J Chromatogr A 2008; 1184:309-22. [DOI: 10.1016/j.chroma.2007.12.032] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Revised: 12/10/2007] [Accepted: 12/13/2007] [Indexed: 10/22/2022]
|
17
|
Structural and thermodynamic investigations of an unusual enantiomeric separation: Lipodex E and compound B. Tetrahedron 2008. [DOI: 10.1016/j.tet.2007.11.069] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
18
|
Gas chromatographic high-throughput screening techniques in catalysis. J Chromatogr A 2007; 1184:160-90. [PMID: 18035362 DOI: 10.1016/j.chroma.2007.10.086] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Revised: 10/09/2007] [Accepted: 10/29/2007] [Indexed: 11/23/2022]
Abstract
Discovering highly efficient catalysts is of great scientific and economical interest. Advances in high-throughput assays in combination with sophisticated analytical techniques have increased the rapidity with which catalysts can be identified and optimized. Understanding how kinetics in the mechanism of catalysis is controlled by structural parameters is essential for a directed design of catalysts. To identify such rate-controlling elementary steps and to develop and refine models, comprehensive experimental kinetic data of a broad variety of substrates are necessary. In the present article concepts of high-throughput screening techniques in catalysis using gas chromatography are reviewed in a survey covering the period from 1998 to 2007. To cover also the origins of concepts and groundbreaking experiments in this research area milestones going back to 1950 are also reviewed. The first part of the review will focus on off-line gas chromatographic analysis, the second part on on-line gas chromatographic analysis covering sequential, parallelized and high-throughput multiplexing gas chromatography. The third part presents recent advances in the integration of chemical transformation and analysis in gas chromatography. The present review article describes the state-of-the-art, scope and limitations, and applications of these different high-throughput screening approaches.
Collapse
|
19
|
Affiliation(s)
- Lingfeng He
- a Advanced Separation Technologies, Inc. , Whippany, New Jersey, USA
| | - Thomas E. Beesley
- a Advanced Separation Technologies, Inc. , Whippany, New Jersey, USA
| |
Collapse
|
20
|
Levkin PA, Levkina A, Czesla H, Nazzi S, Schurig V. Expanding the enantioselectivity of the gas-chromatographic chiral stationary phase Chirasil-Val-C11 by doping it with octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-γ-cyclodextrin. J Sep Sci 2007; 30:98-103. [PMID: 17313147 DOI: 10.1002/jssc.200600279] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Combination of the enantioselective properties of the two versatile gas-chromatographic chiral stationary phases (CSPs) octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-gamma-CD (Lipodex E) 1 and L-valine-diamide-based CSP Chirasil-Val-C11 2 has been realized by doping the chiral polymer 2 with the nonpolymeric selector 1. The resulting mixed-mode CSP Chirasil-Val(gamma-Dex) 3 was found to have a greatly improved enantioselectivity toward proline and aspartic acid (as N-trifluoroacetyl ethyl or methyl esters) in comparison to the single-mode CSP 2. The presence of the CD selector in 3 extended the scope of gas-chromatographic enantioseparations achievable on 2 to underivatized alcohols, terpenes, and other chiral compounds that are exclusively enantioseparated on 1.
Collapse
Affiliation(s)
- Pavel A Levkin
- Institute of Organic Chemistry, University of Tübingen, Tübingen, Germany
| | | | | | | | | |
Collapse
|
21
|
Highly efficient NMR enantiodiscrimination of 1,1,1,3,3-pentafluoro-2-(fluoromethoxy)-3-methoxypropane, a chiral degradation product of sevoflurane, by heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.tetasy.2006.09.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
22
|
Pino V, Lantz AW, Anderson JL, Berthod A, Armstrong DW. Theory and Use of the Pseudophase Model in Gas−Liquid Chromatographic Enantiomeric Separations. Anal Chem 2005; 78:113-9. [PMID: 16383317 DOI: 10.1021/ac051289b] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The theory and use of the "three-phase" model in enantioselective gas-liquid chromatography utilizing a methylated cyclodextrin/polysiloxane stationary phase is presented for the first time. Equations are derived that account for all three partition equilibria in the system, including partitioning between the gas mobile phase and both stationary-phase components and the analyte equilibrium between the polysiloxane and cyclodextrin pseudophase. The separation of the retention contributions from the achiral and chiral parts of the stationary phase can be easily accomplished. Also, it allows the direct examination of the two contributions to enantioselctivity, i.e., that which occurs completely in the liquid stationary phase versus the direct transfer of the chiral analyte in the gas phase to the dissolved chiral selector. Six compounds were studied to verify the model: 1-phenylethanol, alpha-ionone, 3-methyl-1-indanone, o-(chloromethyl)phenyl sulfoxide, o-(bromomethyl)phenyl sulfoxide, and ethyl p-tolylsulfonate. Generally, the cyclodextrin component of the stationary phase contributes to retention more than the bulk liquid polysiloxane. This may be an important requirement for effective GC chiral stationary phases. In addition, the roles of enthalpy and entropy toward enantiorecognition by this stationary phase were examined. While enantiomeric differences in both enthalpy and entropy provide chiral discrimination, the contribution of entropy appears to be more significant in this regard. The three-phase model may be applied to any gas-liquid chromatography stationary phase involving a pseudophase.
Collapse
Affiliation(s)
- Verónica Pino
- Chemistry Department, Iowa State University, 1605 Gilman Hall, Ames, Iowa 50011, USA
| | | | | | | | | |
Collapse
|
23
|
Takahisa E, Engel KH. 2,3-di-O-methoxymethyl-6-O-tert-butyldimethylsilyl-beta-cyclodextrin, a useful stationary phase for gas chromatographic separation of enantiomers. J Chromatogr A 2005; 1076:148-54. [PMID: 15974081 DOI: 10.1016/j.chroma.2005.04.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Heptakis(2,3-di-O-methoxymethyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin (2,3-MOM-6-TBDMS-beta-CD), synthesized by using methoxymethylchloride (MOM-Cl) as derivatization reagent, was used for capillary gas chromatographic separation of enantiomers. The new chiral stationary phase proved to be suitable for the enantiodifferentiation of volatiles from various chemical classes. Compared to the corresponding gamma-CD derivative (2,3-MOM-6-TBDMS-gamma-CD), the spectrum of compounds for which enantiomers could be separated was more limited and the enantioseparation achieved was generally less pronounced. Unusually high separation factors were observed for 2-alkyl esters of short chain acids (C2-C6). Phenomena underlying the enantioseparation of 2-pentyl acetate (alpha: 4.31; 35 degrees C) were investigated by determining thermodynamic parameters. Data show that only one enantiomer is retained significantly on the chiral stationary phase whereas the other one behaves like the hydrocarbons used as references.
Collapse
Affiliation(s)
- Eisuke Takahisa
- Lehrstuhl für Allgemeine Lebensmitteltechnologie, Technische Universität München, Am Forum 2, D-85350 Freising-Weihenstephan, Germany
| | | |
Collapse
|
24
|
Skórka M, Asztemborska M, Zukowski J. Thermodynamic studies of complexation and enantiorecognition processes of monoterpenoids by α- and β-cyclodextrin in gas chromatography. J Chromatogr A 2005; 1078:136-43. [PMID: 16007991 DOI: 10.1016/j.chroma.2005.05.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Gas-liquid chromatography was applied in thermodynamic investigations of processes of complexation and enantioseparation by alpha- and [-cyclodextrins of chiral monoterpenoids. The distribution constants, stability constants and thermodynamic parameters enthalpy, entropy and free energy of the complexation processes were determined. It has been found that enantioseparation of monoterpenes by alpha- and beta-cyclodextrins is the result of formation of 1:2 stoichiometric complexes. When 1:1 stoichiometric complexes are formed, enantioselectivity is not observed. All investigated processes of complexation are enthalpy-driven regardless of the stoichiometry of the formed complexes. -deltaH, -TdeltaS and -deltaG of complexation process have higher values for bicyclic than for monocyclic monoterpenoids as well as for alpha-CD than for beta-CD. The first or second step of complexation may be responsible for enantioselectivity.
Collapse
Affiliation(s)
- Malgorzata Skórka
- Institute of Physical Chemistry of the Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | | | | |
Collapse
|
25
|
Weng W, Zeng Q, Yao B, Wang Q, Li S. Influence of Mobile Phase Composition on the Apparent Thermodynamic Characteristics in Liquid Chromatographic Enantioseparation on a Tartardiamide-Based Stationary Phase. Chromatographia 2005. [DOI: 10.1365/s10337-005-0560-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
26
|
Takahisa E, Engel KH. 2,3-di-O-methoxymethyl-6-O-tert-butyldimethylsilyl-gamma-cyclodextrin: a new class of cyclodextrin derivatives for gas chromatographic separation of enantiomers. J Chromatogr A 2005; 1063:181-92. [PMID: 15700470 DOI: 10.1016/j.chroma.2004.11.068] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Octakis(2,3-di-O-methoxymethyl-6-O-tert-butyldimethylsilyl)-gamma-cyclodextrin (2,3-MOM-6-TBDMS-gamma-CD) was employed as stationary phase for capillary gas chromatographic separation of enantiomers. Selective introduction of the acetal function at positions 2 and 3 of the glucose units was achieved by reaction of 6-O-TBDMS-gamma-cyclodextrin with methoxymethyl chloride. 2,3-MOM-6-TBDMS-gamma-CD was shown to be a chiral stationary phase suitable for enantiodifferentiation of a broad spectrum of chiral volatiles from various chemical classes. A total of 125 pairs of enantiomers could be separated. Structural influences of the analytes on the enantioseparation were demonstrated. High alpha values up to 1.8 were observed for the hydroxyketone acetoin and some methyl branched ketones. Pronounced enantioseparations were also determined for cyclic pentenolone and furanone derivatives.
Collapse
Affiliation(s)
- Eisuke Takahisa
- Lehrstuhl für Allgemeine Lebensmitteltechnologie, Technische Universität München, D-85350 Freising-Weihenstephan, Germany
| | | |
Collapse
|
27
|
McGachy NT, Grinberg N, Variankaval N. Thermodynamic study of N-trifluoroacetyl-O-alkyl nipecotic acid ester enantiomers on diluted permethylated β-cyclodextrin stationary phase. J Chromatogr A 2005; 1064:193-204. [PMID: 15739887 DOI: 10.1016/j.chroma.2004.12.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Thermodynamic studies were performed on 12 pairs of N-trifluoroacetyl-O-alkyl nipecotic acid ester enantiomers on diluted permethylated beta-cyclodextrin stationary phase (CP Chirasil-Dex CB). The influence of ester alkyl group structure on interaction with permethylated beta-cyclodextrin (Me-CD) and enantioselectivity was studied. The types of alkyl groups studied included n-alkyl (C1-C5) and groups containing branching at differing locations relative to the chiral center of the molecule. The results show that for a given molecular weight, the n-alkyl esters have stronger interactions with Me-CD than esters containing branched alkyl groups. However, although having weaker interactions with Me-CD, esters containing alpha-branched alkyl groups exhibit higher enantioselectivity than the corresponding n-alkyl or beta-branched isobutyl esters. From the retention data, thermodynamic parameters were estimated using the retention increment method and enthalpy-entropy compensation plots (ln R' versus deltaH) were constructed. The results suggest that ester enantiomers with branching at the alpha-carbon of the ester alkyl group have additional and/or different types of enantioselective interactions with Me-CD than the C1-C5 n-alkyl esters or beta-branched isobutyl ester. In order to obtain a qualitative sense of the interaction with Me-CD, structures of the diastereomeric complexes formed between Me-CD and some of the ester enantiomers were modeled using simulated annealing molecular dynamics.
Collapse
Affiliation(s)
- Neil T McGachy
- Merck Research Laboratories, Merck & Co., Inc., P.O. Box 2000, Rahway, NJ 07065, USA.
| | | | | |
Collapse
|
28
|
Jiang Z, Crassous J, Schurig V. Gas-chromatographic separation of tri(hetero)halogenomethane enantiomers. Chirality 2005; 17:488-93. [PMID: 16113994 DOI: 10.1002/chir.20191] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Five-atomic tri(hetero)halogenomethanes represent the simplest class of non-isotopic small chiral molecules suitable for the study of fundamental aspects of chirality. The analytical gas-chromatographic separation of the enantiomers of bromochlorofluoromethane 1 and of chlorofluoroiodomethane 2 on the immobilized chiral stationary phase octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-gamma-cyclodextrin 3, chemically linked to polydimethylsiloxane, is described. By temperature-dependent thermodynamic measurements very low isoenantioselective temperatures T(iso) are found and for optimum enantiomeric separations cryogenic temperatures are required. The ee values of enantiomerically enriched tri(hetero)halogenomethanes 1 and 2 are determined and relative configurations are correlated with the chromatographic elution order of 1 and 2 on 3.
Collapse
Affiliation(s)
- Zhengjin Jiang
- Institute of Organic Chemistry, University of Tübingen, Morgenstelle 18, D-72076 Tübingen, Germany
| | | | | |
Collapse
|
29
|
Levkin PA, Ruderisch A, Schurig V. Combining the enantioselectivity of a cyclodextrin and a diamide selector in a mixed binary gas-chromatographic chiral stationary phase. Chirality 2005. [DOI: 10.1002/chir.20219] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
30
|
Schurig V. Contributions to the theory and practice of the chromatographic separation of enantiomers. Chirality 2005; 17 Suppl:S205-26. [PMID: 15952137 DOI: 10.1002/chir.20133] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The theory and practice of enantioselective capillary chromatography employing metal coordination compounds and modified cyclodextrins as chiral stationary phases are treated. A unified approach involving all contemporary chromatographic methods and a single enantioselective column is described. Reliable thermodynamic data of enantioselectivity are derived by the retention-increment method. The existence of an isoenantioselective temperature is demonstrated. Kinetic enantiomerization studies are presented. The preparative-scale separation of enantiomers by gas chromatography with enantioselective packed columns is achieved. Unusual phenomena and future aspects of enantioselective chromatography are discussed.
Collapse
Affiliation(s)
- Volker Schurig
- Institute of Organic Chemistry, University of Tübingen, Tübingen, Germany.
| |
Collapse
|
31
|
Weng W, Wang QH, Yao BX, Zeng QL. Enantioseparation of amino acid derivatives on an immobilized network polymer derived from l-tartaric acid. J Chromatogr A 2004; 1042:81-7. [PMID: 15296391 DOI: 10.1016/j.chroma.2004.05.058] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Seven structurally related amino acid derivatives were successfully enantioseparated by HPLC with a commercially available column containing a chiral immobilized network polymer derived from L-tartaric acid. The experiments were carried out under normal-phase conditions. All the solutes could be baseline separated using n-hexane/2-propanol (95/5) as eluent at a flow rate of 1 ml/min at 25 degrees C, with reasonable retention time (<12 min). The effects of the polar alcohol modifier (type and content) in the mobile phase and the column temperature on the enantioseparation were studied. Apparent thermodynamic parameters were also calculated from the plots of ln alpha or ln k' versus 1/T. Some mechanistic aspects of chiral recognition were discussed with respect to the structures of the solutes. It was found that the enantioseparations are all enthalpy driven, and the N-acyl groups of the solutes have significant influence on the chiral recognition.
Collapse
Affiliation(s)
- Wen Weng
- Department of Chemistry, Zhangzhou Teachers College, Zhangzhou 363000, China.
| | | | | | | |
Collapse
|