What is E-Z isomerism?

E-Z isomerism, also known as cis-trans isomerism or geometric isomerism, is a type of stereoisomerism found in organic chemistry. It occurs when there is restricted rotation around a double bond or a ring structure, resulting in different spatial arrangements of substituent groups attached to the double bond or ring.

In E-Z isomerism:

E stands for "entgegen," which is German for "opposite." This configuration refers to groups on opposite sides of the double bond.
Z stands for "zusammen," which is German for "together." This configuration refers to groups on the same side of the double bond.
The determination of whether a compound is E or Z is based on the Cahn-Ingold-Prelog priority rules, which assign priorities to substituent groups based on the atomic number of the atoms directly attached to the double-bonded carbons. The E isomer has higher priority groups on opposite sides of the double bond, while the Z isomer has higher priority groups on the same side of the double bond.

E-Z isomerism is important in understanding the properties and behaviors of organic compounds, particularly in areas such as stereochemistry and chemical synthesis.