Optical enrichment sublimation

Sublimation. Such effects can also be seen in solid-gas interphase. Scheme 30 shows the consequences of fractional sublimation of partially resolved L-mandelic acid (47). The optical purity could be enhanced or reduced, depending on the optical purity of the starting material. Since the eutectic point of mandelic acid is obtained with about a 75 25 enantiomer ratio, such a mixture is more readily sublimed than the racemate or conglomerate. Scheme 30 gives other examples of optical enrichment by sublimation. Phenyl 1-phenyl-1-propyl sulfide in 6% ee affords the sublimed compound in 74% ee, but the residue is... 

One-pot synthesis, prostaglandins, 302 Opiates, 36 Optical enrichment chromatography, 285 sublimation, 280... 

Fractionation resulting from partial sublimation of optically active samples has also been described27 29 and, more recently, modest chiral self-recognition was observed even in liquids during distillation30-31. In this case distillation of propyl 2-hydroxypropanoate (8.55% R) resulted in a distilled fraction which was enriched in the f -isomer (9.11 % 81.79% ee), while the residue was deficient in the / -isomer (7.83% 84.34% ee)31. 

After filtration, the alcohol enriched in one enantiomer was obtained from the filtrate, the other one was isolated from the solid complex. Thermal methods such as distillation or sublimation were used for liberation of the optically active alcohols from the complexes. [38] Time-scaled experiments showed continous increasing of the enantiomeric excess (ee) in the crystalline diastereoisomeric complexes of 26 and 8 for 14 days, then these ee values practically did not change within the next 16 days (Figure 1). 

---