This is the only monoclinic centrosymmetric point group. The mirror plane perpendicular to the twofold rotation axis is indicated by a thick solid line around the edge of the projection line. As result of the mirror symmetry, points above and below the plane are co-incident. The figure below has the same symmetry, but is with the twofold rotation axis shown in the plane of the screen. The mirror plane is then perpendicular to the plane of the screen as shown below. The white circle in the centre of each figure indicates the centre of inversion.
(You may like to compare these figures to the symmetry of trans CHBr=CHBr shown earlier.)
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| © Copyright 1997-2006. Birkbeck College, University of London. | Author(s): Jeremy Karl Cockcroft |