PL 5 - Organic Reactions

Question 1

How do you hydrolyse esters by acid hydrolysis?

Answer 1

Acid hydrolysis of an ester is the reverse of esterification
- The ester is heated under reflux with dilute aqueous acid (i.e. H2SO4)
- Water hydrolyses the ester, with the acid acting as a catalyst. This forms and alcohol and a carboxylic acid
CH3COOCH3 + H2O –> CH3COOH + CH3OH

Question 2

How do you hydrolyse esters by alkali hydrolysis?

Answer 2

• Also known as saponification
• The ester is heated under reflux with aqueous hydroxide ions (i.e. from NaOH)
• This will form an alcohol and a salt of the carboxylic acid
  CH3COOCH3 + NaOH –> CH3COO-Na+ + CH3OH

Question 3

How do you hydrolyse amides by acid hydrolysis?

Answer 3

Heat with aqueous acid, this forms a carboxylic acid and ammonium chloride:
CH3CONH2 + H2O + HCl –> CH3COOH + NH4Cl

Question 4

How do you hydrolyse primary amides by alkali hydrolysis?

Answer 4

• Heat with NaOH(aq)
• This forms ammonia and the salt of the carboxylic acid:
  CH3CONH2 + NaOH –> CH3COO-Na+ + NH3

Question 5

How do acyl chlorides react with alcohols?

Answer 5

An acyl chloride reacts with alcohol to form an ester and hydrochloric acid:
RCOCl + CH3OH –> RCOOCH3 + HCl

Question 6

How do acyl chlorides react with amines?

Answer 6

An acyl chloride reacts with a primary amine to form a secondary amide and hydrochloric acid:
RCOCl + CH3NH2 –> RCO-NHCH3 + HCl