What is a saturated hydrocarbon?

• A. Hydrocarbon with only single bonds
• B. Hydrocarbon with only double bonds
• C. Hydrocarbon with aromatic ring
• D. Hydrocarbon with mixed bonds

Answer: (A)

Saturated hydrocarbons have the maximum number of hydrogen atoms attached to the carbon chain, which happens when all carbon–carbon bonds are single bonds. This makes them alkane molecules, with the general idea that every carbon is bonded to as many hydrogens as possible. If you have a double bond between carbons, the molecule can’t hold as many hydrogens, so it’s unsaturated (like alkenes). An aromatic ring, such as benzene, is also considered unsaturated because the carbon bonds are part of a delocalized π system that reduces the number of hydrogens relative to a fully saturated ring. A hydrocarbon with mixed bonds has some double bonds as well, so it isn’t fully saturated either.