Figure 1.5
Symmetry at carbon building blocks.
The two mirror image representations of a carbon atom with four different groups attached to it are depicted in figure 1.6. Imagine aligning the grey carbon atoms and the red and green groups of the two molecules; the blue and white groups are now opposite each other. As expected* the molecule is chiral. Mirror image related molecules are called enantiomers.
Figure 1.6
A chiral carbon atom and its mirror image.
Previously (ST240* Book 1* page 105* Activity 10)* you have seen that organic molecules can change their shape through rotations around single bonds. As no bonds need to be broken in this process* the different arrangements do not create new compounds. By contrast* keeping the same atoms but altering the way they are bonded to each other creates isomers.
n Are enantiomers isomers?
n Answer
Compounds with chiral carbon atoms fall within a class of isomers called stereoisomers. As with all isomers* a pair of stereoisomers contain the same atoms. Unlike other classes of isomers* the atom connectivities in a pair of stereoisomers is also the same. Stereoisomers only differ in the three dimensional arrangement of the groups bonded to one or more atoms in the molecule.