Final answer:
CH₃COOH forms dimers through hydrogen bonding between the hydroxyl group's hydrogen of one molecule and the carbonyl group's oxygen of another molecule.
Step-by-step explanation:
The hydrogen bonding of CH₃COOH involves connections between the hydrogen atom of one acetic acid molecule's hydroxyl group (OH) and the oxygen atom of another acetic acid molecule's carbonyl group (C=O). These specific hydrogen bonds are what enable acetic acid molecules to form dimers, especially in the gas phase. In these dimers, each acetic acid molecule is both a hydrogen bond donor (through the OH group) and an acceptor (through the C=O group), which result in a stable, dimeric structure.