Alcohols (CIE A Level Chemistry)

• Acyl chlorides are reactive organic compounds with a -COCl functional group
• The carbonyl carbon is electron-deficient and has a partial positive charge
• It is therefore susceptible to nucleophilic attack
• The carbon-chlorine bond breaks and white fumes of hydrogen chloride, HCl, are formed

Reaction with alcohols and phenols

• Acyl chlorides react with alcohols and phenols to form esters in a nucleophilic substitution reaction
• The -OH group acts as a nucleophile and attacks the carbonyl carbon to substitute the chlorine atom
• Forming esters from acyl chlorides rather than carboxylic acids is more effective because::
  • Acyl chlorides are more reactive (so it produces the ester faster)
  • Acyl chloride reactions go to completion (so more of the ester is produced)

Reaction with alcohols

• The reaction of acyl chlorides with alcohols is vigorous and white fumes of HCl gas are formed

Acyl chlorides react vigorously with alcohols to form esters

Reaction with phenols

• For the reaction of acyl chlorides with phenols to occur, heat and a base are required
  • The base is needed to deprotonate the phenol and form a phenoxide ion
  • The phenoxide ion is a better nucleophile than the original phenol molecule and will be able to attack the carbonyl carbon

Acyl chlorides react with phenols when heated and in the presence of a base to form esters

A base is needed to form a phenoxide ion which is a better nucleophile than phenol; now, nucleophilic attack on the carbonyl carbon can more readily occur