A Level Chemistry OCR Practice Exam

Which type of hydrocarbon has a ring structure?

1. Aliphatic hydrocarbon

2. Aromatic hydrocarbon

3. Alicyclic hydrocarbon

4. Cyclic alkane

The correct answer is: Alicyclic hydrocarbon

Alicyclic hydrocarbons are characterized by having a ring structure while still being classified as aliphatic. These compounds can contain one or more rings composed entirely of carbon atoms, and they can exhibit properties similar to both aliphatic and aromatic hydrocarbons, depending on the presence of double bonds and the degree of saturation. Cyclic alkanes, which could also be considered in this context, specifically refer to saturated hydrocarbons with one or more rings but are often lumped into the broader category of alicyclic compounds. The distinction lies primarily in the terminology; however, both terms indicate a hydrocarbon structure featuring a ring. Aromatic hydrocarbons, on the other hand, feature conjugated pi-electron systems that allow for resonance, creating unique stability and distinct chemical behavior often associated with benzene derivatives. Aliphatic hydrocarbons lack this ring system and encompass linear and branched structures without any rings. Therefore, the most precise and widely accepted term for hydrocarbons that form a ring structure is indeed alicyclic hydrocarbons, making the choice robust and accurate in this context.