Shapes of Molecules
This chapter focuses on the spatial arrangement of the atoms within the molecule. It looks more closely at certain types of covalent bonding and examines some of the more common geometric possibilities that occur in organic molecules. There are two main types of bonding, ionic and covalent. Each covalent bond is formed from a molecular orbital that may accommodate a maximum of two electrons. For every bonding molecular orbital that is formed, there is an anti-bonding molecular orbital formed as well. Most importantly, the geometry of the anti-bonding orbital will often determine the line of approach for the incoming reagent, and so will impose certain restrictions on the way a mechanism must proceed. Tetrahedral geometry is the commonest geometry that is encountered in organic molecules, because this is the shape that is adopted by a saturated carbon, that is, one that is bonded to four other groups by four single bonds.