Question

What is $\mathrm{E}-\mathrm{Z}$ isomerism?

Answer 1

Isomerism:

• “The phenomenon of the existence of two or more compounds possessing the same molecular formula but different properties is known as isomerism.”
• Such compounds are called isomers.

$\mathrm{E}-\mathrm{Z}$ isomerism:

• It is a type of stereoisomerism.
• It applies to alkene which contains C=C double bond and two different groups on both end.

Rules for $\mathrm{E}-\mathrm{Z}$ system:

• The atoms or groups attached to each olefinic carbon are given priority as per the sequence rule.
• If the higher priority groups are present on same sides across the double bond, the geometrical isomer is said to have $\mathrm{Z}-$configuration or 'cis'.
• If the higher priority groups are present on opposite sides across the double bond, the geometrical isomer is said to have $\mathrm{E}-$configuration or 'trans'.
• For example: