A Level Chemistry OCR Practice Exam

What type of isomerism is characterized by different spatial arrangements of groups attached to each carbon of a C=C double bond due to restricted rotation?

1. Cis-trans isomerism

2. Chain isomerism

3. E/Z isomerism

4. Functional group isomerism

The correct answer is: E/Z isomerism

The type of isomerism characterized by different spatial arrangements of groups attached to each carbon of a C=C double bond due to restricted rotation is known as E/Z isomerism. This form of stereoisomerism arises specifically from the presence of a double bond, where the groups attached to the carbons of the double bond can orient themselves in different ways. In E/Z isomerism, the terms "E" (from the German "entgegen," meaning opposite) and "Z" (from "zusammen," meaning together) are used to specify the relative positions of the highest priority substituents attached to the double-bonded carbons. When the highest priority groups on each carbon are on opposite sides of the double bond, the isomer is labeled as E. Conversely, if they are on the same side, the isomer is labeled as Z. This distinction is crucial because it influences the physical and chemical properties of the compounds, making E/Z isomerism a significant area of study in stereochemistry. The other types of isomerism mentioned—chain isomerism, which involves different arrangements of carbon skeletons; and functional group isomerism, which involves different functional groups—do not involve the spatial arrangement around