Identifying the Hydroxyl Group in Ethanol

Given

• Molecular structure: CH3CH2OH

• The -OH is bonded directly to a carbon atom.

Find

The functional group present, the compound's name, and its organic family.

Principle

A functional group is an atom or group of atoms that gives a molecule its characteristic chemistry. An -OH group bonded to a carbon atom is the hydroxyl group, and any molecule containing it belongs to the alcohol family. Alcohols are named from the longest carbon chain with the suffix -ol.

Formula

Solution

1. Locate the characteristic group: the -OH attached to the CH2 carbon is the hydroxyl functional group.

2. A molecule with a hydroxyl group bonded to carbon belongs to the alcohol family.

3. Count the longest carbon chain: 2 carbons → root 'eth-' with the alcohol suffix '-ol' → ethanol.

4. Confirm: CH3CH2OH is the two-carbon alcohol, commonly known as ethanol.

Unit check

Functional-group identification is qualitative, so no units apply; the structural check is that the formula CH3CH2OH contains exactly one -OH on a two-carbon chain, matching the name ethanol.

What this means physically

The hydroxyl group defines the alcohols, a family whose hydrogen bonding gives them much higher boiling points than similar-size alkanes — ethanol boils at 78 C while ethane boils at -89 C. Recognizing -OH on sight is the first step in predicting an organic molecule's behavior.