[25.3] the chemistry of phenol

Question 1

describe the structure of phenol

Answer 1

• non-bonding electrons on the oxygen atom in the phenol group are drawn into the benzene ring
• the lone pair becomes part of the delocalisation increasing the electron density in the ring

Question 2

describe the physical appearance of pure phenol

Answer 2

• white crystalline solid
• smells of disinfectant
• has to be handled with great care as it causes immediate white blistering to the skin
• crystals are often rather moist and pink

Question 3

describe the mp / bp and solubility of phenol

Answer 3

• melting and boiling points are higher for phenol than methylbenzene
• phenol is slightly water soluble

Question 4

describe the reactions of phenol as an acid

Answer 4

• phenol is a weak acid
• a hydrogen ion can break away from the -OH group and transfer to a base
• phenols are more acidic than alcohols but less than carboxylic acids

Question 5

draw the reaction of phenol with sodium hydroxide

Answer 5

• sodium phenoxide + H₂O
• on top of the benzene ring there is a O⁻Na⁺

Question 6

draw the reaction of phenol with sodium

Answer 6

• 2 sodium phenoxide + H₂O
• on top of the benzene ring there is a O⁻Na⁺
• make sure it is balanced

Question 7

describe the reaction of phenol with bromine

Answer 7

• phenols undergo electrophilic substitution reactions
• they take place under milder conditions and more readily than benzene
• no catalyst needed and room temp
• decolourises bromine water and form a white precipitate of 2,4,6-tribromophenol

Question 8

why is no catalyst needed in the reaction of phenol with bromine?

Answer 8

• the increased reactivity of phenol is due to the fact that, in solution, the lone pair of electrons from the oxygen atom are drawn into the delocalised ring
• this increases its overall electron density

Question 9

what are the products in the reaction of phenol with dilute HNO₃?

Answer 9

• 2-nitrophenol
• 4-nitrophenol