When phenol is treated with excess bromine water, the product formed is:

2, 4, 6-Tribromophenol

The correct answer is option 4. 2, 4, 6-Tribromophenol.

When phenol is treated with excess bromine water, the major product formed is 2,4,6-tribromophenol (option 4). This is because bromination of phenol with excess bromine water leads to the substitution of all available hydrogen atoms in the benzene ring, resulting in the formation of tribromophenol.