Symmetry Elements and Optical Isomerism

Although we have followed conventional practice—and for general purposes will continue to do so—in setting out four kinds of symmetry elements and operations, a, /, C , and Sny we should note that the list can in principle be reduced to only two C and S . A reflection operation can be regarded as an 

SM operation, that is. the (trivial) rotation by together With reflection. 

Tk Optltol SitoS ttie ioWomg elect on a general point, x, y, z. We 

All symmetry operations that we wish to consider can be regarded as either proper or improper rotations. 

Molecules that are not superimposable on their mirror images are termed dissymmetric. This term is used rather than asymmetric, since the latter means, literally, have no symmetry that is, it is applicable only to a molecule belonging to point group Cx. All asymmetric molecules are dissymmetric, but the converse is not true. Dissymmetric molecules can and often do possess some symmetry. It is possible to give a very simple, compact rule expressing the relation between molecular symmetry and dissymmetric character  

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