C3H4 C3H4 C3H4
View down 2 axis View down -4 axis View down 2′ axis

The two double bonds in allene results in two methylene groups at 90 degrees to each other. The main symmetry axis is -4, colinear with a twofold rotation axis. Perpendicular to the -4 axis are 2 twofold axis which are bisected by two mirror planes.

The point-group symmetry for this molecule is given the crystallographic symbol -4 2 m.

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