Carboxylic Acids and Derivatives: Carboxylic Acids and Esters - Reactions of Esters

Question 1

What does hydrolysis mean?

Answer 1

• Hydrolysis is a reaction where a bond is broken using water

Question 2

What type of catalysts are used to speed up the hydrolysis of esters?

Answer 2

• Acids (acid hydrolysis)

- Alkalis (base hydrolysis)

Question 3

What conditions are needed for acid hydrolysis of esters?

Answer 3

• Dilute acid catalyst

- Under reflux

Question 4

Give the general word equation for acid hydrolysis

Answer 4

• Ester + water ⇌ carboxylic acid + alcohol
• Reflux and acid catalyst on top of ⇌
• Esters broken into the carboxylic acid and alcohol they were formed from

Question 5

What conditions are needed for base hydrolysis of esters?

Answer 5

• Dilute base

- Under reflux

Question 6

Give the general word equation for the base hydrolysis of esters

Answer 6

• Ester + OH- → carboxylate ion* + alcohol
• Reflux above →
• *Becomes sodium salt

Question 7

Give the general structural formula of base hydrolysis

Answer 7

• RCOOR’ + OH- → RCOO- + R’OH

- Reflux above →

Question 8

Give the word and structural equation for the base hydrolysis of methyl ethanoate

Answer 8

• Methyl ethanoate + OH- → ethanoate ion* + methanol
• CH3COOCH3 + OH- → CH3COO- + CH3OH
• Reflux above →
• *CH3COO- becomes CH3COONa (sodium salt)

Question 9

Give the word and structural equation for the acid hydrolysis of methyl ethanoate

Answer 9

• Methyl ethanoate + water ⇌ ethanoic acid + methanol

- CH3COOCH3 + H2O ⇌ CH3COOH + CH3OH

Question 10

Is acid or base hydrolysis more favoured?

Answer 10

• Base hydrolysis
• Equilibrium lies more to the right hand side and the reaction is quicker
• In acid hydrolysis, the reaction is reversible so the equilibrium doesn’t lie as far to the right

Question 11

Which alcohol are the esters of vegetable oils and animal fats made from?

Answer 11

• Propane-1,2,3-triol

- AKA glycerol

Question 12

Which biological molecules makes up animal fats and vegetable oils?

Answer 12

• Triglycerides

Question 13

What type of organic compound makes up the fatty acids in triglycerides?

Answer 13

• Carboxylic acids

- Can be saturated or unsaturated

Question 14

Do the 3 fatty acid chains in a triglyceride have to be made of the same carboxylic acids?

Answer 14

• No

Question 15

What is saponification?

Answer 15

• The base hydrolysis of a triglyceride (using sodium hydroxide) to form glycerol and the sodium salts of the long chained carboxylic acids
• The sodium salts (e.g sodium stearate) are used to make soap

Question 16

Give the general word equation for the hydrolysis of fats and oils (triglycerides)

Answer 16

• Fat/oil + 3Sodium hydroxide → glycerol + 3sodium salt

Question 17

Give the equation for the hydrolysis of the fat/oil in the CGP textbook, page 430

Answer 17

• I don’t have Brainscape Pro so I can’t put a photo here soz

Question 18

What is biodiesel used for? What crops is it made from?

Answer 18

• Renewable fuel

- Made from oils from crops like rape seed

Question 19

What type of organic compound does biodiesel contain?

Answer 19

• Biodiesel is a mixture of methyl esters of long-chain carboxylic acids

Question 20

How are biodiesels formed?

Answer 20

• Fats/oils are reacted with methanol, using a strong alkali catalyst
• E.g potassium hydroxide or sodium hydroxide

Question 21

Give the general word equation for the formation of biodiesel

Answer 21

• Fat/oil + 3methanol → glycerol + 3methyl ester

Question 22

Give the general structural equation for the formation of biodiesel

Answer 22

• (H2COOCR)(HCOOCR)(H2COOCR) + 3CH3OH → (H2COH)(HCOH)(H2COH) + 3RCOOCH3
• Potassium hydroxide above →
• Look at CGP, page 430 if unclear