In Benzene:
* Benzene is a non-polar solvent: It cannot form hydrogen bonds with benzoic acid.
* Hydrogen bonding within benzoic acid: Benzoic acid molecules can form strong hydrogen bonds between the carboxyl group (COOH) of one molecule and the carbonyl group (C=O) of another. This intermolecular hydrogen bonding leads to the formation of dimers.
* Favorable interactions: The dimer formation in benzene is favored because it minimizes the exposure of the polar carboxyl group to the non-polar environment, leading to a more stable configuration.
In Water:
* Water is a polar solvent: Water molecules can form strong hydrogen bonds with the carboxyl group of benzoic acid.
* Competition for hydrogen bonding: The strong hydrogen bonding between benzoic acid and water molecules competes with the hydrogen bonding between benzoic acid molecules, making dimer formation less favorable.
* Favorable interactions: Benzoic acid molecules prefer to interact with water molecules through hydrogen bonding, which is more energetically favorable than forming dimers.
Summary:
The difference in solvent polarity and the ability to form hydrogen bonds leads to the formation of benzoic acid dimers in benzene but not in water. The non-polar nature of benzene favors dimerization, while the polar nature of water promotes hydrogen bonding between benzoic acid and water molecules, preventing dimer formation.
