B6 - Phenol

Question 1

Why is phenol classified as a weak acid?

Answer 1

When dissolved in water, phenol partially dissociates forming the phenoxide ion and a proton.

Question 2

The product of phenol reacting with sodium hydroxide:

Answer 2

A salt, sodium phenoxide, and water

Question 3

What type of reaction is phenol with sodium hydroxide?

Answer 3

A neutralisation reaction

Question 4

What is observed when phenol reacts with bromine water?

Answer 4

Decolourisation of bromine water
White precipitate formed (of 2,4,6-tribromoohenol)

Question 5

Conditions for bromination of phenol?

Answer 5

Room temperature
Halogen carrier catalyst is NOT required

Question 6

Product of nitration of phenol?

Answer 6

A mixture of both:
2-nitrophenol
And
4-nitro-phenol
Both with water

Question 7

Conditions for nitration of phenol?

Answer 7

Room temperature

Question 8

Reactant for nitration of phenol?

Answer 8

Dilute HNO3 (rather than conc in benzene)
No H2SO4 needed

Question 9

Is phenol less or more reactive than benzene?

Answer 9

More reactive than benzene

Question 10

What causes the increased reactivity in phenol?

Answer 10

-Lone pair of electrons on O p-orbital of -OH group are donated into the pi-system of the carbon ring
-The electron density of the benzene ring in phenol is increased
-The increased electron density attracts electrophiles more strongly than with benzene
-The aromatic ring is therefore more susceptible to attack from electrophiles than in benzene

Question 11

Why does bromination of phenol not require a halogen carrier catalyst?

Answer 11

The electron density in the phenol ring structure is sufficient to polarise bromine molecules.

Question 12

Where is an ortho directing group?

Answer 12

On position 2

Question 13

Where is a meta directing group?

Answer 13

On position 3

Question 14

Where is a para directing group?

Answer 14

On position 4

Question 15

Which relevant groups are ortho and para directing?

Answer 15

• OH (phenol)
• NH2/NHR (amine)
• Halogen
• R (alkyl group)

Question 16

Which relevant groups are meta directing?

Answer 16

• NO2 (nitro)