Carboxylic acid derivatives

Question 1

What is a carboxylic acid derivative?

Answer 1

• A compound that can be hydrolysed to form the parent carboxylic acid.
• They have a common sequence of atoms, known as an acyl group (a carbon bonded to an R group and double bonded to an oxygen.

Question 2

How are esters named?

Answer 2

• Named after the parent carboxylic acid from which it is derived. Remove -oic acid suffix and replace with -oate. The alkyl chain attached to the single bonded oxygen is then added as the first word in the name.

Question 3

How are acyl chlorides named?

Answer 3

• Named after the parent carboxylic acid from which it is derived. To name an acyl chloride, remove the ‘-oic acid’ suffix from the parent carboxylic acid and replace with ‘-oyl chloride.’

Question 4

How are acid anhydrides formed?

Answer 4

• Formed by the removal of water from two carboxylic acid molecules by the reaction of the -OH component of their -COOH groups.

Question 5

Describe acid hydrolysis of esters.

Answer 5

• The ester is heated under reflux with dilute aqueous acid.
• The ester is broken down by water, with the acid acting as a catalyst.
• Produces an the constituent alcohol and carboxylic acid monomers.
• Reverse of esterification

Question 6

Describe alkaline hydrolysis of esters.

Answer 6

• Also known as saponification.
• Irreversible.
• The ester is heated under reflux with aqueous hydroxide ions.
• Produces carboxylate ions and alcohol.

Question 7

How are acyl chlorides prepared?

Answer 7

• Prepared directly from their parent carboxylic acids with thionyl chloride (SOCl2)
• The other products are SO2 and HCl are evolved as gases.

Question 8

How do acyl chlorides react?

Answer 8

• React with nucleophiles by losing the chloride ion whilst retaining the C=O double bond.

Question 9

How can esters be made from acyl chlorides?

Answer 9

• Acyl chloride + alcohol –> ester + HCl
• Acyl chloride + phenol –> aromatic ester + HCl

Question 10

How can carboxylic acids be made from acyl chlorides?

Answer 10

• Acyl chloride + H2O –> carboxylic acid + HCl

Question 11

How can amides be made from acyl chlorides?

Answer 11

• Acyl chloride + NH3 –> primary amide + NH4CL
• Acyl chloride + primary amine –> secondary amide + alkylammonium chloride

Question 12

How do acid anhydrides react?

Answer 12

• In a similar way to acyl chlorides with alcohols, phenols, water, ammonia and amines.
• Less reactive than acyl chlorides.

Question 13

How do acyl chlorides react with nucleophiles?

Answer 13

• Acyl chloride + water.
• C=O bond opens, allowing the central carbon to form a bond with H2O.
• The oxygen donates one of its lone pairs to reform the C=O bond.
• The Cl and a H from the H2O are eliminated.
• Carboxylic acid and H+ and Cl- formed.
• Nucleophilic addition-elimination.