Some Generalizations Regarding Optical Activity

Consider two solutions - A and B. Solution A contains a pure enantiomer, and solution B contains the enantiomer of the compound in solution A. Let s say that solution A exhibited positive rotation. 

Since the solution A containing a pure enantiomer exhibits positive rotatory properties, its enantiomer will have negative rotatory properties. What can we conclude about these compounds Well, we can be certain that both compounds present in the solutions A and B are chiral, since they exhibit optical activity. 

The specific rotation [ a ] of a compound at a given wavelength is denoted by 

---

Before continuing, some words must be said with regard to the terms rare earths and f elements used in this chapter. The term rare earths includes the elements Sc, Y and the lanthanides La through Lu. However, this chapter solely deals with divalent or trivalent rare-earth ions which are optically active, i.e., possess a partially filled f-shell. Thus, although the term rare earths is used in this chapter, it should be kept in mind that the elements Sc, Y, La, and Lu are excluded. In some exceptional cases the more general term f elements will be used, as for example when high pressure studies on actinide ions with a partially filled 5f shell are discussed. There are only few studies on 5f elements in non-metallic compounds under pressure, however, it seems interesting to compare the results found for these ions with those for the 4f-elements. 

---