What is hyperconjugation?

1 Answer
Truong-Son N.
Jul 22, 2017

Hyperconjugation is an extended delocalization of electron density from a #sigma# bond into an adjacent, non-full #p# nonbonding or #pi# orbital that stabilizes the resultant compound.

A common instance of this occurs in organic chemistry on carbocations.

Adjacent alkyl groups contain #"C"-"H"# #sigma# bonds that will interact with the central empty #p# nonbonding orbital in the carbocation to stabilize the electropositive carbon by providing negative charge density:

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Thus, the more alkyl groups around the carbocation (e.g. the more substituted the carbocation), the more stable it is, i.e.

#3^@ > 2^@ > 1^@ > "methyl"# #"carbocation"#,

the tertiary carbocation is more stable than the secondary, which is more stable than the primary, which is more stable than the methyl carbocation.

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