17.4.4 - Phenol Flashcards
What conditions are required for the bromination of phenol?
Room temperature and pressure with no catalyst.
What observations can be made when bromine water reacts with phenol?
The bromine water is decolourised.
A white precipitate is formed.
What 2 products are formed when phenol reacts with bromine?
2,4,6 - tribromophenol
Hydrogen bromide.
Why does phenol react more readily with bromine than benzene does?
The oxygen in the hydroxyl group has a lone pair of electrons and these electrons can merge with the electrons in the delocalised pi system.
Increased electrons density in the delocalised pi system means that the molecule is activated and so is much more reactive towards electrophiles.
Bromine is polarised as it approaches the molecule so the Br+ electrophile attacks the ring.
Phenol reacts faster than phenylmethanol in electrophilic substitution reactions.
Explain why this is so.
The lone pair of electrons on the oxygen atom donate their electrons to the ring.
This increases the electron density.
In phenylmethanol, the oxygen is too far from the ring to donate its electrons.
In phenol, the lone pair on oxygen atom overlaps with electrons in the delocalised pi system.
Explain why phenol can be nitrated using milder conditions than benzene.
The electron density of the ring in phenol is greater than in benzene.
Because the lone pair of electrons on oxygen overlap with electrons in the delocalised pi system.
Explain why 4-nitrophenol has a higher boiling point than 2-nitrophenol.
They both form hydrogen bonds.
In 4-nitrophenol the hydrogen bonds join molecules in a straight chain so are stronger.
