Chemistry

Cis–trans isomerism arises from restricted rotation around a double bond — the $\pi$ bond prevents the two groups on each carbon from freely spinning past each other. When two different groups are attached to each carbon of the double bond, they can be arranged on the same side (cis) or opposite sides (trans), creating distinct molecules with different properties. The key is that this rigidity is permanent under normal conditions, unlike single bonds where rotation is easy.

Cis–trans isomerism arises from restricted rotation around a double bond — the $\pi$ bond prevents the two groups on each carbon from freely spinning past each other. When two different groups are attached to each carbon of the double bond, they can be arranged on the same side (cis) or opposite sides (trans), creating distinct molecules with different properties. The key is that this rigidity is permanent under normal conditions, unlike single bonds where rotation is easy.