18.1 Carboxylic acids

Question 1

Test

Answer 1

• reacts with carbonates to form CO2 gas which will turn limewater milky

Question 2

Production of carboxylic acids

Answer 2

1) Oxidation of primary alcohols and aldehydes (by either acidified K2Cr2O7 or KMnO4 and reflux)
2) Hydrolysis of nitriles (by either dilute acid or dilute alkali, followed by acidification)
3) Hydrolysis of esters (by either dilute acid or dilute alkali, followed by acidification)

Question 3

Oxidation of primary alcohols and aldehydes (by either acidified K2Cr2O7 or KMnO4 and reflux)

Answer 3

1) Primary alcohol = aldehyde + carboxylic acid

2) Aldehyde = carboxylic acid

Question 4

Hydrolysis of nitriles (by either dilute acid or dilute alkali, followed by acidification)

Answer 4

1) Nitrile + acid (usually HCI) + water = carboxylic acid + ammonium chloride salt

2) Nitrile + alkali (hydrolysed) + water= sodium carboxylate salt + ammonia

• sodium carboxylate salt can be acidified to carboxylic acid

Question 5

Hydrolysis of esters (by either dilute acid or dilute alkali, followed by acidification)

Answer 5

1) Ester + water (reversible rxn) = carboxylic acid + alcohol

2) Ester + alkali hydrolyzed (usually NaOH) + heat = sodium carboxylate salt + alcohol

*sodium carboxylate salt can be acidified to carboxylic acid

Question 6

Dissociation of carboxylic acids

Answer 6

• eqm lies to the left
• they are weak acids that don’t fully dissociate in water + solution formed has a pH value of less than 7
• drawing in notes

Question 7

Reactions of carboxylic acids

Answer 7

1) Redox reactions with reactive metals
2) Neutralisation reactions with alkalis
3) Acid-base reactions with carbonates
4) Esterification with alcohols
5) Reduction by LiAIH4

*reactions in notes

Question 8

Redox reactions with reactive metals

Answer 8

carboxylic acid + M = salt + hydrogen gas

Question 9

Neutralisation reactions with alkalis

Answer 9

carboxylic acid + NaOH = salt + water

Question 10

Acid-base reactions with carbonates

Answer 10

carboxylic acid + carbonate = salt + water + CO2 gas

Question 11

Esterification with alcohols (H2SO4 as a catalyst)

Answer 11

alcohol + carboxylic acid = ester + H2O

Question 12

Reduction by LiAIH4

Answer 12

Carboxylic acid + [H] = primary alcohol + H2O