Final answer:
The dimerization of acetic acid molecules to form (CH3COOH)2 is due to hydrogen bonding and is favored at lower temperatures due to the exothermic nature of the process.
Step-by-step explanation:
The student has asked about the structure of the dimer formed by acetic acid in the gas phase and the conditions that favor this dimerization.
Acetic acid (CH3COOH) molecules can form a structure known as a dimer, represented as (CH3COOH)2, through the process of hydrogen bonding. In the dimer, the hydrogen atom of one acetic acid molecule forms a bond with the oxygen atom of another acetic acid molecule, represented by a dashed line in chemical diagrams. The hydrogen bond between the two molecules is responsible for the formation of the dimer.
Temperature plays a significant role in the dimerization process. Typically, dimerization is an exothermic process, which implies that it releases heat; therefore, it is favored at lower temperatures. At higher temperatures, the additional thermal energy can overcome these intermolecular forces, leading to the dissociation of the dimer into monomers.