Axis of rotation-reflection

In the Schoenfiies system the improper axis is an axis of rotation-reflection (see page 52). In the Internationa) system the axis of rotatory inversion ( ) is ore of n-fold rotation followed by inversion (see Fig. 3.29). 

Molecules possessing an axis of rotation-reflection (S ) are said to display reflection symmetry, meaning that they are superimposable on their reflection or mirror image. This property is tested by means of the symmetry operation known as rotation-reflection the latter operation involves two manipulations, namely rotation of 360°/ about an axis designating S , followed by reflection through a mirror plane perpendicular to S . Thus, rrcww-dichloroethylene (II) possesses an S2 axis since... 

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See also in sourсe #XX -- [ ]

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