[25.3] the chemistry of phenol
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describe the structure of phenol
• 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
describe the physical appearance of pure phenol
• 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
describe the mp / bp and solubility of phenol
• melting and boiling points are higher for phenol than methylbenzene • phenol is slightly water soluble
describe the reactions of phenol as an acid
• 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
draw the reaction of phenol with sodium hydroxide
• sodium phenoxide + H₂O • on top of the benzene ring there is a O⁻Na⁺
draw the reaction of phenol with sodium
• 2 sodium phenoxide + H₂O • on top of the benzene ring there is a O⁻Na⁺ • make sure it is balanced
describe the reaction of phenol with bromine
• 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
why is no catalyst needed in the reaction of phenol with bromine?
• 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
what are the products in the reaction of phenol with dilute HNO₃?
• 2-nitrophenol • 4-nitrophenol