Which of the following functional groups is characteristic of alkenes?

• A. Carbon-carbon triple bond $C\equiv C$
• B. Carbon-carbon double bond $C=C$
• C. Hydroxyl group $O-H$
• D. Carbonyl group $C=O$

Answer: (B)

Verified step by step guidance

1. Recall that alkenes are hydrocarbons that contain at least one carbon-carbon double bond as their defining functional group.
2. Identify the functional groups listed: a carbon-carbon triple bond (alkyne), a carbon-carbon double bond (alkene), a hydroxyl group (alcohol), and a carbonyl group (aldehyde or ketone).
3. Understand that the carbon-carbon triple bond is characteristic of alkynes, not alkenes.
4. Recognize that the hydroxyl group (-OH) is characteristic of alcohols, and the carbonyl group (C=O) is characteristic of aldehydes and ketones.
5. Conclude that the carbon-carbon double bond (C=C) is the functional group that defines alkenes.