Enantiomeric Purity by Gas Chromatography

Aliquots (200 pL) of the well stirred reaction mixture were removed periodically and added to a 2 mL vial containing 1.5 mL of MTBE. Hydrochloric acid (20 pL of 1 N) was added, the vial was shaken and then the solvent was dried over anhydrous MgS04 and the solution was transferred into a vial. Five drops of methanol and 1 drop of trimethylsilyldiazomethane solution (2 M in hexane) were added to convert the carboxylic acid product into the methyl ester for GC analysis. A J W Scientific Cyclodex B column (0.25 micron, 30 meterx0.25 mm) was used. GC conditions 110°C for 10 min then l°C/min for 5 min. Retention times (S)-methyl ester 8.35, (R)-methyl ester 8.65, (S)-ethyl ester 11.35, and the (R)-ethyl ester at 11.64 min. 

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Cohen, N., Scott, C.G., Neukom, R.J., Lopresti, G., Weber, G. and Saucy, G. (1981) Total synthesis of all eight stereoisomers of alpha-tocopheryl acetate. Determination of their diastereoisomeric and enantiomeric purity by gas chromatography. Helv. Chim. Acta 64 1158-1173. 

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