Which statement correctly distinguishes primary, secondary, and tertiary alcohols by the number of carbon atoms attached to the carbon bearing the hydroxyl group?

Which statement correctly distinguishes primary, secondary, and tertiary alcohols by the number of carbon atoms attached to the carbon bearing the hydroxyl group?

• A. Secondary—two; Primary—one; Tertiary—three
• B. Primary—one carbon; Secondary—two; Tertiary—three
• C. Tertiary—three; Secondary—two; Primary—one
• D. Primary—four; Secondary—two; Tertiary—three

Answer: (B)

Alcohols are classified by how many carbon groups are attached to the carbon that bears the hydroxyl group. The OH-bearing carbon can be bonded to one, two, or three carbon atoms, and that number defines the type of alcohol. If that carbon is bonded to one carbon, it’s a primary alcohol; if it’s bonded to two carbons, it’s a secondary alcohol; if it’s bonded to three carbons, it’s a tertiary alcohol. For example, methanol and ethanol are primary because the carbon with OH is attached to only one other carbon; isopropanol is secondary because the OH-bearing carbon is connected to two carbons; tert-butanol is tertiary because the OH-bearing carbon has three carbon neighbors. This description matches the statement Primary—one carbon; Secondary—two; Tertiary—three.

Alcohols are classified by how many carbon groups are attached to the carbon that bears the hydroxyl group. The OH-bearing carbon can be bonded to one, two, or three carbon atoms, and that number defines the type of alcohol. If that carbon is bonded to one carbon, it’s a primary alcohol; if it’s bonded to two carbons, it’s a secondary alcohol; if it’s bonded to three carbons, it’s a tertiary alcohol. For example, methanol and ethanol are primary because the carbon with OH is attached to only one other carbon; isopropanol is secondary because the OH-bearing carbon is connected to two carbons; tert-butanol is tertiary because the OH-bearing carbon has three carbon neighbors. This description matches the statement Primary—one carbon; Secondary—two; Tertiary—three.