Which arrangement of atoms is found in all alcohols?

• A. C-H
• B. C-O-C
• C. C-OH
• D. H-O-H

Answer: (C)

Alcohols are defined by a hydroxyl group (-OH) bound to a carbon atom. This -OH group is the feature shared by all alcohols, giving the general structure R-OH where R is a carbon-containing group. Because of this, the arrangement C-OH uniquely identifies alcohols. The other options don’t define alcohols: a C-H bond is common in many molecules and doesn’t specify an alcohol; a C-O-C linkage is typical of ethers; and H-O-H is water, which has no carbon.