Does the energy barrier cause the existence of two distinct isomers?

Question

Ellie Adams · Accepted Answer

Yes, the energy barrier for rotation about the double bonds in alkenes causes the existence of two distinct isomers.

The π bond of an alkene is stable because the electrons are attracted to both carbon nuclei.

Rotation about the C=C axis breaks the π bond and puts one #p# electron on each carbon atom.

This takes energy of about 200 kJ/mol.

The average kinetic energy of a molecule at room temperature is about 4 kJ/mol.

This is not enough energy to break the pi bond, so alkenes like but-2-ene can exist as distinct cis and trans isomers.

Ava Andrews · Answer

undefined Yes, the energy barrier can cause the existence of two distinct isomers. Isomers are molecules that have the same molecular formula but different arrangements of atoms. In some cases, isomers can exist due to the presence of an energy barrier that prevents rapid interconversion between them. This barrier can arise from factors such as steric hindrance or differences in bond strength. As a result, the isomers may have different energy states, with one being more stable than the other. The presence of this energy barrier allows both isomers to coexist, with the more stable isomer being favored under certain conditions.