# Alkenes: Properties

## Alkenes: Stability

The stability of alkenes increases with the number of alkyl substituents at the . The data for butene isomers ($C4H8$) are shown in the table below.

Tab.1
Butene isomers, listed in order of increasing stability
 Alkene $ΔH°$ [ $kJmol-1$] Fig.1-butene Fig. cis-2-butene Fig. trans-2-butene Fig.isobutene + 1.2 - 5.7 -10.0 -14.0

The stability gain of alkenes with increasing alkyl substitution at the double bond is due to , which is caused by the interaction of one of the four $sp3$-hybrid orbitals of the $CH3$ group with the π* orbital of the double bond.

Fig.1
Hyperconjugation
Page 2 of 4