Why are trans alkenes more stable than cis alkenes?

Trans alkenes are typically more stable than cis alkenes due to steric effects and torsional strain.

Steric Effects: In a trans alkene, the bulky substituents are farther apart from each other compared to a cis alkene, where they are closer together. This increased distance reduces the repulsive interactions between the substituents, leading to greater stability. In cis alkenes, the closer proximity of the bulky groups can lead to steric hindrance, which destabilizes the molecule.

Torsional Strain: In cis alkenes, the torsional strain resulting from the interaction between the substituents can be higher than in trans alkenes. Torsional strain occurs when substituents try to occupy the same space, causing repulsion between them. This strain contributes to the overall destabilization of the molecule. In trans alkenes, the arrangement allows for a more favorable distribution of electron density, reducing torsional strain.

Overall, the combination of reduced steric hindrance and torsional strain makes trans alkenes more stable compared to cis alkenes.