P

Pi Bond

π bond: sideways p-p orbital overlap; present in double and triple bonds
Quick Reference
Formula / Notationπ bond: sideways p-p orbital overlap; present in double and triple bonds
Also Known AsPi bond, π bond, lateral overlap bond, pi-electron bond

What is Pi Bond?

A covalent bond formed by sideways overlap of p orbitals, creating regions of electron density above and below the internuclear axis. Pi bonds are weaker than sigma bonds and cannot rotate freely. They are found in double bonds (one π bond) and triple bonds (two π bonds).

Formula & Notation

π bond: sideways p-p orbital overlap; present in double and triple bonds

Other Names / Synonyms: Pi bond, π bond, lateral overlap bond, pi-electron bond

Properties & Characteristics

A pi (π) bond is a covalent bond formed by the lateral (side-on) overlap of two p orbitals on adjacent atoms, creating electron density above and below the internuclear axis. A π bond has a nodal plane containing the nuclei. Pi bonds form in addition to σ bonds in double bonds (1σ + 1π) and triple bonds (1σ + 2π). Rotation around a π bond is restricted (barrier to rotation ~270 kJ/mol for C=C), explaining cis-trans isomerism. Pi bonds are weaker than σ bonds.

Uses & Applications

Pi bonds are central to: organic chemistry (alkene and alkyne reactions: electrophilic addition, cycloaddition), aromatic chemistry (delocalised π systems in benzene), conjugation and chromophore design (dye and drug chromophores depend on π→π* transitions), organometallic chemistry (η² to η⁶ ligand binding via π electrons), and molecular electronics (conductive π-conjugated polymers).

Safety Information

Compounds with reactive π bonds (strained alkenes, alkynes, cumulenes) can react explosively or rapidly under the right conditions. Acrolein (CH₂=CHCHO) is a bis-electrophilic toxic compound due to its conjugated π system. Allylic and vinylic radicals from π bond homolysis are reactive species.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Pi Bond
Formula π bond: sideways p-p orbital overlap; present in double and triple bonds
Synonyms Pi bond, π bond, lateral overlap bond, pi-electron bond

Frequently Asked Questions

A covalent bond formed by sideways overlap of p orbitals, creating regions of electron density above and below the internuclear axis. Pi bonds are weaker than sigma bonds and cannot rotate freely. They are found in double bonds (one π bond) and triple bonds (two π bonds).

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