What is the Difference Between Resonance and Tautomerism?

Resonance and tautomerism are important chemical concepts that involve the distribution of electrons and the structures of chemical compounds. They have some similarities but also several key differences:

Resonance:

• Refers to the presence of several forms of the same chemical compound, which determines the actual structure of the compound.
• Occurs due to the interaction between lone pairs of electrons and bond electrons.
• Resonance structures can be obtained by relocating bond electrons and lone electron pairs.
• Has a profound effect on the stability of the molecule.
• Affects bond length (single bond is shortened while the double bond becomes longer).
• Resonance is a hypothetical phenomenon.
• Resonance structures do not have any atoms moved, and the arrangement of electrons in the significant resonance contributors does not match any conventional Lewis structure.

Tautomerism:

• Refers to the presence of two (or more) forms of the same compound that are capable of interconversion.
• Occurs in planar or non-planar molecules.
• Tautomers can be obtained by relocating a proton (and electrons).
• Has no effect on the stability of the molecule.
• Has no effect on bond length.
• Tautomerism is a real phenomenon (tautomers exist in reality).
• Tautomers exist in equilibrium with each other.

In summary, resonance deals with the interaction between lone pairs of electrons and bond electrons, while tautomerism involves the interconversion of two or more forms of the same compound. Resonance has a significant effect on the stability and bond length of a molecule, whereas tautomerism does not.

Comparative Table: Resonance vs Tautomerism

The main difference between resonance and tautomerism is that resonance deals with the delocalization of electrons in a molecule, leading to multiple equivalent Lewis structures, whereas tautomerism involves the rapid interconversion between isomers due to the migration of atoms. Here is a table summarizing the differences between resonance and tautomerism:

In summary, resonance structures are different ways to depict the electronic distribution in a molecule, while tautomers are true isomers that can interconvert with each other due to the migration of atoms.