Pie and Sigma bond _Carbon and ItsCompound
Pie bond is formed by the sideways overlapping of orbitals. In
pie bonds, the electron density also concentrates between the atoms, but on
either side of the line joining the two atoms. the shape of the molecule is
determined by the sigma bonds but not by the pie bonds. Pie bond in fact
shortens the bond length. A double bond is made up of one sigma bond and one
pie bond. A triple bond is made up of one sigma bond and two pie bonds. Thus
the multiple bonds in a molecule are called pie bonds. Pie bonds are found in
unsaturated hydrocarbons. For example in ethene (CH2=CH2),
there is a double bond between the two carbon atoms. This double bond actually
consists of one sigma bond and one pie bond. Similarly in ethyne (CHa"CH),
there is a triple bond between the two carbon atoms. This triple bond consists
of one sigma bond and two pie bonds. The formation of pie bonds is shown below
The sigma bond is a bond formed by head to head overlap of
orbitals. In sigma bonds the electron density is concentrated in between the
two atoms. The sigma bond in a molecule is denoted
by a single bond. Hence in a molecule, all the single bonds are
sigma bonds. For example in ethane (CH3-CH3), there are
seven single bonds. So, there are seven sigma bonds in ethane (six C-H and one
C-C). Thus saturated hydrocarbons possess only sigma bonds. The formation of
sigma bonds is shown below