Phenol

Question 1

How does phenol act in water and what is the equilibria equation?

Answer 1

Acts as a weak acid that dissociates in water

- C6H5OH + H2O C6H5O- + H3O+

Question 2

why are phenols stronger acids than alcohols??

Answer 2

The ethoxide ion readily accepts protons to form ethanol because oxygen is more electron dense and therefore better at holding onto proton than oxygen in Phenol. Positive inductive effect of surrounding electrons stronger in ethanol than phenol.

MORE DISSOCIATION OF HYDROGEN ION IN PHENOL THAN IN ALCOHOLS

Question 3

Why is phenol more reactive than benzene??

Answer 3

• More reactive than benzene towards electrophiles
• INTERACTION between LONE PAIRS on oxygen atom and the ring increases availability of electrons in the aromatic ring as they are DELOCALISED from p orbital into the ring
• Increased ELECTRON DENSITY as a result, therefore able to induce dipoles on halogens unlike benzene.

Question 4

Reaction of phenol and sodium hydroxide

Answer 4

Weak acid reacts readily with strong bases to form salt and water
Phenol + NaOH -> sodium phenoxide + water
(hydrogen on OH group replaced with Na, and hydrogen ion forms water with OH ion)

Question 5

Why will phenol react with sodium hydroxide but not sodium carbonate??

Answer 5

Phenol is a weak acid that must react with a strong acid to form salt and water, NaOH is a strong base whilst Na2CO3 is a weak base, therefore unable react.

Question 6

Describe Reaction of Phenol with sodium.

Answer 6

2Phenol + 2Na -> 2Sodium phenoxide + H2

Question 7

Describe the Bromination of phenol

Answer 7

Phenol + 3 Br2 -> 2,4,6 tribromophenol + 3HBr

-decolourises bromine water

Question 8

How do you recognise 2,4,6 tri-bromophenol

Answer 8

White precipitate that is insoluble in water

Question 9

What can phenol do that benzene can’t do to molecules

Answer 9

Polarise them due to increased electron density from donated lone pair electrons, therefore they react without the presence of a catalyst