Enantiomers optical activity

In the absence of special syimnetry, the phase mle requires a minimum of tliree components for a tricritical point to occur. Synnnetrical tricritical points do have such syimnetry, but it is easiest to illustrate such phenomena with a tme ternary system with the necessary syimnetry. A ternary system comprised of a pair of enantiomers (optically active d- and /-isomers) together with a third optically inert substance could satisfy this condition. While liquid-liquid phase separation between enantiomers has not yet been found, ternary phase diagrams like those shown in figure A2.5.30 can be imagined in these diagrams there is a necessary syimnetry around a horizontal axis that represents equal amounts of the two enantiomers. 

Chiral stationary phases for the separation of enantiomers (optically active isomers) are becoming increasingly important. Among the first types to be synthesized were chiral amino acids ionically or covalently bound to amino-propyl silica and named Pirkle phases after their originator. The ionic form is susceptable to hydrolysis and can be used only in normal phase HPLC whereas the more stable covalent type can be used in reverse phase separations but is less stereoselective. Polymeric phases based on chiral peptides such as bovine serum albumin or a -acid glycoproteins bonded to... 

Cyclic compounds Depending on the type of substitution on a ring, the molecule can be chiral (optically active) or achiral (optically inactive). For example, 1,2-dichlorocyclohexane can exists as meso compounds (optically inactive) and enantiomers (optically active). If the two groups attached to the ring are different, i.e. no plane of symmetry, there will be four isomers. 

Pure enantiomer optically active inverted mirror image configuration... 

Pure enantiomer optically active alcohol is protonated to optically active oxonium ion. 

Aminotransferases have high stereoselectivity for a given enantiomer. Optically active l- or D-amino acids are produced stereoselectively the process is a chiral synthesis, not a resolution. 

Convergent resolution of enantiomers. Trost et al. have devised an enantio-convergent prostanoid synthesis from 1, in which a 1,3-hydroxy shift interconverts the two enantiomers. The interconversion was conducted on the urethane of 1 with (S)-l-a-naphthylethylamine catalyzed with mercury(II) trifluoroacetate. The equilibrium ratio of 2 to 3 is about 2 1. By repetition of this equilibration optically active 1 can be obtained without loss of one enantiomer. Optically active 1 was used for synthesis of the optically pure prostanoid 4. 

---