How do saturated and unsaturated hydrocarbons differ in their bonding?

• A. Saturated hydrocarbons contain C=C double bonds.
• B. Saturated hydrocarbons contain both single and double bonds.
• C. Saturated hydrocarbons contain only C-C single bonds; unsaturated hydrocarbons contain at least one C=C double bond.
• D. Unsaturated hydrocarbons contain only C-C single bonds.

Answer: (C)

Saturated hydrocarbons are made up of carbon–carbon single bonds only. Each carbon forms four single bonds, so no pi bonds are present and the molecule has as many hydrogens as possible for its carbon framework. Unsaturated hydrocarbons, on the other hand, contain at least one carbon–carbon double bond (and sometimes triple bonds). A double bond adds a pi component and reduces the number of hydrogens that can attach to the carbons. So the defining difference is that saturated hydrocarbons have only C–C single bonds, while unsaturated hydrocarbons have at least one C=C double bond. For example, methane and ethane are saturated; ethene and ethyne are unsaturated. The other statements would imply double bonds exist in saturated or that unsaturated have only single bonds, which isn’t correct.