C2H2F2Br2 C2H2F2Br2 C2H2F2Br2
View down 2 axis Oblique view View perpendicular to 2 axis

This example is of interest in that the point symmetry of the molecule is the same irrespective of any torsional rotation about the C-C single bond. The only symmetry element is the twofold rotation axis. You should note that the whole molecule is enantiomorphic since each carbon atom is chiral in the same sense. Compare the symmetry of this molecule to that of the non-enantiomorphic R,S′ CHFCl-CHFCl molecule, where the chirality of the two carbon atoms "cancel" each other out.

The point-group symmetry for this molecule is given the crystallographic symbol 2.

© Copyright 1997-2006.  Birkbeck College, University of London. Author(s): Jeremy Karl Cockcroft