differences between tautomerism and resonance

• Tautomerism involves making and breaking of a sigma as well as pi bond. While in resonance, only the electrons in pi bonds or lone- pairs n heteroatoms shift; the sigma framework is not disturbed. This difference results in a shift of an atom from one position to another in tautomerism. In resonance there is no shift of any atom.

 

• Tautomerism may involve a change in hybridisation of atoms resulting in a change in shape of the molecule. In resonance there is no change in hybridisation of the geometry.

 

• The two tautomeric forms exist together though the equilibrium may shift to either side with a change in condition. The tautomers have a physical reality whereas the resonance structures are imaginary.