Which term describes a hydrocarbon in which other elements replace hydrogen atoms?

• A. Substituted Hydrocarbon
• B. Alcohol
• C. Amino Acid
• D. Ester

Answer: (A)

Hydrocarbons are built from carbon and hydrogen. When one or more of those hydrogen atoms are replaced by other elements or groups, the resulting molecule is a substituted hydrocarbon. This naming highlights the idea that the basic hydrocarbon skeleton stays the same, but some hydrogens have been swapped for something else, like chlorine or hydroxyl groups. For example, replacing a hydrogen in methane with chlorine gives chloromethane, a substituted hydrocarbon. The other terms refer to specific types of compounds with distinct functional groups—an alcohol has a hydroxyl group, an amino acid is a biomolecule with amino and carboxyl groups, and an ester contains the R-COOR group—so they don’t describe the general idea of hydrogen replacement in a hydrocarbon.