Pi Bond
A covalent bond formed by the sideways overlap of parallel p orbitals, with electron density above and below the internuclear axis.
Unit
kJ/mol
In depth
Sideways overlap is less effective than head-on, so pi bonds are weaker than sigma bonds and are broken first in addition reactions. Because the two lobes must stay parallel, a pi bond locks the molecule against rotation, which is the origin of cis–trans isomerism in alkenes.
Examples in the real world
The second bond of ethene's C=C; the two pi bonds in the N≡N triple bond; the delocalised pi cloud of benzene.