25.3 Chemistry of Phenol

Question 1

What is the chemical formula of phenol?

Answer 1

C₆H₅OH

Question 2

Draw the skeletal formula of phenol:

Answer 2

Question 3

What is the IUPAC name for this molecule?

Answer 3

2-nitrophenol

Question 4

What is the IUPAC name for this molecule?

Answer 4

2-phenylethanol

Question 5

What is the IUPAC name for this molecule?

Answer 5

2,4,6-tribromophenol

Question 6

What is the IUPAC name for this molecule?

Answer 6

2-hydroxybenzoic acid

Question 7

Why is phenol considered a weak acid?

Answer 7

Phenol + Water ⇌ Phenoxide ion + Hydrogen ion

has the ability to partially dissociate in water to release H⁺

Question 8

What happens when phenol is added to water?

Answer 8

Phenol + Water ⇌ Phenoxide ion + Hydrogen ion

partial dissociation

Question 9

Rank these molecules from strongest to weakest acid:

phenol, carboxylic acid, alcohol

Answer 9

(strongest)

1. Carboxylic acid
2. Phenol
3. Alcohol

(weakest)

Question 10

Using reactions with weak & strong bases, describe the difference in acid strength of alcohols, carboxylic acids & phenols:

Answer 10

• alcohols not strong enough to react with strong base, ∴ weakest
• phenols can react with strong base only
• carboxylic acids can react with strong bases & even weak bases, ∴ strongest

Question 11

The weaker the base, the ___ the acid required to react with it.

Answer 11

stronger

Question 12

What are the conditions for electrophilic substitution of phenols?

Answer 12

room temperature

(does not require halogen carrier)

Question 13

Why can electrophilic substitution in phenols take place under milder conditions than that of benzene?

Answer 13

phenol is more reactive:

• lone pair from :OH donated to ring of delocalised 𝛑-electrons
• phenol’s aromatic ring has higher electron density than benzene’s
• greater attraction for electrophiles/polarising ability
  
  • ∴ reactions of phenol can take place under milder conditions

Question 14

Name 2 types of electrophilic substitution reactions of phenol:

Answer 14

1. Bromination
2. Nitration

Question 15

Write a chemical equation for the bromination of phenol:

Answer 15

• C₆H₅OH + 3Br₂ ⟶ C₆H₂Br₃OH + 3HBr

decolourises bromine water, forms white precipitate

Question 16

Write a chemical equation for the nitration of phenol:

Answer 16

• C₆H₅OH + HNO₃ ⟶ C₆H₄NO₂OH + H₂O

Question 17

Describe & explain the differences in reactivity of benzene & phenol:

Answer 17

• phenol more reactive than benzene
  
  • lone pair on :OH donated to ring of delocalised 𝛑-electrons
  • aromatic ring in phenol has higher electron density than that of benzene
  • phenol has greater attraction for electrophiles/polarising ability