Which among the following compounds is most soluble in water?

Ethylene glycol

The correct answer is Option (4) → Ethylene glycol

Water solubility increases with:

• Ability to form hydrogen bonds

• Number of –OH groups

More –OH groups → more hydrogen bonding → more solubility.

Multiple Hydroxyl Groups: Ethylene glycol contains two hydroxyl (-OH) groups, whereas ethanol and phenol only have one.

Increased Hydrogen Bonding: Solubility in water is directly related to the ability of a compound to form hydrogen bonds with water molecules. Having two -OH groups allows ethylene glycol to form a greater number of hydrogen bonds compared to the other options, leading to higher solubility.

Miscibility: While ethanol is also highly soluble (miscible in all proportions), the presence of more polar functional groups per molecule generally increases the strength of interaction with water

Option 1: Ethanol - Has one –OH group. Forms hydrogen bond → soluble.

Option 2: Ethane - Non-polar hydrocarbon. Cannot form hydrogen bonds. Insoluble.

Option 3: Phenol - Has one –OH group but large benzene ring reduces solubility.

Option 4: Ethylene glycol - Has two –OH groups. Forms strong hydrogen bonding with water. Most soluble.