Which of the following functional groups contains exactly $1$ carbon atom?

• A. Ether
• B. Aldehyde
• C. Ketone
• D. Carboxylic acid

Answer: (B)

Verified step by step guidance

1. Identify the number of carbon atoms present in each functional group by analyzing their general structures.
2. For an ether, the general structure is R–O–R', where R and R' are alkyl groups; since both R and R' contain at least one carbon, ethers have at least two carbon atoms in total.
3. For an aldehyde, the general structure is R–CHO, where the carbonyl carbon (C=O) is bonded to a hydrogen and an alkyl or hydrogen group; if R is hydrogen, the aldehyde contains exactly one carbon atom (formaldehyde).
4. For a ketone, the general structure is R–CO–R', where the carbonyl carbon is bonded to two alkyl groups; this means ketones always have at least three carbon atoms in total.
5. For a carboxylic acid, the general structure is R–COOH, where the carbonyl carbon is bonded to a hydroxyl group and an alkyl group; the smallest carboxylic acid (formic acid) has one carbon atom, but generally, the functional group includes at least one carbon plus the R group.