Chapter 26: Carboxylic Acids and Esters

Question 1

What functional group do carboxylic acids have, and what does this contain?

Answer 1

• Carboxyl groups
• They contain both a carbonyl and hydroxyl group bonded to the same carbon atom, which is what makes them react differently

Question 2

Are carboxylic acids soluble? Explain why.

Answer 2

• The C=O and O-H bonds are polar, which allows carboxylic acids to form hydrogen bonds with the water molecules and dissolve in water
• However, once there are more than 4 carbon atoms in a carboxylic acid molecules, the solubility decreases as the non-polar carbon chain has a greater effect

Question 3

What type of carboxylic acids are more soluble than the others, and why?

Answer 3

• Dicarboxylic acids
• They have 2 polar carboxyl groups to form hydrogen bonds

Question 4

What happens when carboxylic acids dissolve in water? What does this mean?

Answer 4

• They partially dissociate
• They are weak acids

Question 5

Give the equation for the dissociation of methanoic acid, including state symbols.

Answer 5

• HCOOH (aq) <-> H+ (aq) + HCOO- (aq)

Question 6

Which reactions do carboxylic acids have in common with other acids?

Answer 6

• Redox reactions with metals
• Neutralisation reactions with bases (alkalis, metal oxides and carbonates)

Question 7

What ion do carboxylic acids form in their salt compounds?

Answer 7

• Carboxylate ions

Question 8

What observations can be made during the reaction of carboxylic acids with metals?

Answer 8

• The metal dissolves
• Effervescence

Question 9

What observations can be made during the reaction of carboxylic acids with carbonates?

Answer 9

• The carbonate dissolves if the carboxylic acid is in excess
• Effervescence

Question 10

How can carboxylic acids be told apart from other organic compounds? Why does this method work?

Answer 10

• They are reacted with carbonates
• They are the only common organic compound that is acidic enough to react with carbonates

Question 11

List 4 derivatives of carboxylic acids, and the functional group of each.

Answer 11

• Esters, COO
• Acyl chlorides, COCl
• Acid anhydrides, COOCO
• Amides, CON

Question 12

What causes carboxylic acid derivatives to react in similar ways?

Answer 12

• They all have an acyl group (RC=O) bonded to an electronegative atom

Question 13

How are esters formed? What is this reaction called?

Answer 13

• Alcohol + carboxylic acid -> ester + water
• Conditions: heat and sulfuric acid catalyst
• Esterification

Question 14

How are esters named?

Answer 14

• The alcohol’s name changes to end in -yl (e.g. methyl)
• The name of the carboxylic acid changes to end in -oate (e.g. propanoate)
  (-E.g. methyl propanoate)