Bromobenzene is a complete compound, bromophenyl is a description of a unit in a larger compound
Chemists abbreviate some groups to simplify the names of more complex compounds. So while bromobenzene is a complete name for a compound, bromophenyl signals that the unit occurs as part of a larger compound.
In this case–to abuse strict chemical terminology a little–there is a bromobenzene unit attached to to 2 carbon on an ethanol unit and attached at the 2-carbon on the bromobenzene unit so we say 2-bromophenyl not the more complicated "bromobenzene with the hydrogen at the two position replaced by an ethanol unit with the connection being made at the 2-position on the ethanol."
- Bromobenzene has a molecular formula C6H5Br, while 2-(2-Bromophenyl)ethanol has a molecular formula C8H9BrO.
- Bromobenzene has a molecular mass of 157.01 g/mol, while 2-(2-Bromophenyl)ethanol has a molecular mass of 201.06 g/mol.
- In Bromophenyl, a hydrogen from benzene ring is replaced by a functional group, in this case ethanol.