Replacing a hydrogen atom in a hydrocarbon with chlorine produces what class?

• A. Alkanes
• B. Halogenated hydrocarbons
• C. Alkyne derivatives
• D. Aromatic hydrocarbons

Answer: (B)

Introducing a chlorine atom in place of a hydrogen turns the molecule into a halogenated hydrocarbon. The defining feature here is the presence of a halogen substituent, not the presence of a specific type of carbon–carbon bonding. So any product formed by replacing hydrogen with chlorine is categorized as a halogenated hydrocarbon (often called a haloalkane if the main chain is aliphatic). It isn’t simply an alkane, because the chlorine changes the classification by adding a halogen substituent. It isn’t necessarily an alkyne derivative, unless a triple bond is involved, and while chlorinated aromatics exist, they are still halogenated hydrocarbons.