Gas chromatographic separation of saturated aliphatic hydrocarbon enantiomers on permethylated ?-cyclodextrin

Abstract

Enantiomers of chiral aliphatic hydrocarbons are generally difficult to separate because they lack functional groups to be derivatized in order to generate diastereomers. The systematic and quantitative separation of a series of branched hydrocarbon enantiomers using a chiral cyclodextrin stationary phase and a cryostat-controlled gas chromatograph is described. The use of a cryogenic system allows the improvement of separations for various chiral aliphatic hydrocarbons. The molecular cyclodextrin-based mechanism of the achieved enantiomeric separations is discussed briefly. Possible applications of this analytical technique are summarized, with special emphasis on the planned enantiomeric separation experiment on a cometary nucleus.

Evaluation of enantioselective gas chromatography for the determination of minute deviations from racemic composition of α‐amino acids with emphasis on tyrosine: Accuracy and precision of the method

“…The precise determination of measurable deviations from racemic compositions is also of paramount interest in the search for homochirality in extraterrestrial environments in ongoing space-related campaigns, i.e., the Rosetta mission, 22 or in forthcoming space explorations such as Chirons of Titan 23 and Exo-Mars. 24,25 Because the enantiomers of a-amino acids are prone to racemization over the course of time, the ee of extraterrestrial amino acids, had it in fact originally existed, could well be minute.…”

Contributions to the theory and practice of the chromatographic separation of enantiomers

“…A gaschromatographic column containing Chirasil-b-Dex 9 for analysis of chiral aliphatic hydrocarbons is part of the payload of the ESA Rosetta mission currently on its way to the comet Churimov -Gerasimienko. 69 The use of open tubular capillary columns coated with Chirasil-b-Dex 9 for enantiomeric separation by electromigration represented the first instance of enantioselective capillary electromatography (o-CEC). 70,71 By utilizing Chirasil-b-Dex 9 as CSP in o-CEC, a dual chiral recognition system has been accomplished by adding a second chiral selector as chiral mobile phase additive (CMPA) to the buffer.…”

Combining the enantioselectivity of a cyclodextrin and a diamide selector in a mixed binary gas‐chromatographic chiral stationary phase

“…2 -4 Apart from the fact that Chirasil-Dex is enantioselective toward many classes of chiral compounds, such as underivatized alcohols, ketones, lactones, and alkyl halides, it is one of the very few selectors capable of resolution of chiral saturated aliphatic hydrocarbons lacking any functional groups. 5 In spite of this, enantioselectivity of the Chirasilb-Dex toward proteinogenic amino acid derivatives (like N-trifluoroacetyl ethyl esters) is quite moderate; only six out of 16 investigated specimens were enantioseparated with a z 1.02 using a standard temperature program. By contrast, the diamide-type selectors 6 -8 Chirasil-Val 9 and Chirasil-Calix-Val 10 (cf.…”

“…However, these selectors fail to separate racemates lacking hydrogen-bonding functional groups. Taking into account the importance of the simultaneous enantioseparation of chiral unfunctionalized hydrocarbons and chiral amino acids in the search for extraterrestrial homochirality in various space explorations (Rosetta, 5 Titan, 11,12 and ExoMars 13,14 ), it appears challenging to try to combine the enantioselectivities of the cyclodextrin inclusion-type selector and diamide-type selector by applying them simultaneously in one gas-chromatographic column.…”