How to Test for Chirality Planes of Symmetry

Which atom is the chirality center of (a) limonene and (b) of thalidomide  

Which atoms in each of the following molecules are chirality centers  

The ultimate way to test for molecular chirality is to construct models of the molecule and its mirror image and then determine whether they are superposable. If the two models are superposable, the molecule that they represent is achiral. If the models are not superposable, then the molecules that they represent are chiral. We can apply this test with actual models, as we have just described, or we can apply it by drawing three-dimensional structures and attempting to superpose them in our minds. 

There are other aids, however, that will assist us in recognizing chiral molecules. We have mentioned one already the presence of a single chirality center. Other aids are based on the absence of certain symmetry elements in the molecule. 

The plane may pass through atoms, between atoms, or both. For example, 2-chloropropane has a plane of symmetry (Fig. 5.Sa), whereas 2-chlorobutane does not (Fig. 5.8b). 

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How To Test for Chirality Planes of Symmetry 201 5.7A How To Assign (R) and (S) Configurations 202 5.12A How To Draw Stereoisomers for Molecules Having More Than One Chirality Center 218 5.12C How To Name Compounds with More Than One Chirality Center 222... 

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