Esters

Question 1

What is an ester?

Answer 1

A derivative of carboxylic acids where the hydroxyl H is replaced with an alkyl group

Question 2

What is esterification?

Answer 2

Making esters

Question 3

How do we make esters from carboxylix acids?

Answer 3

Carboxylic acid + alcohol <—> ester + water
Need c. H2SO4 catalyst and heat
Methanoic acid + propan-1-ol
HCOOH + CH3CH2COOH <–> HCOOCH2CH2CH3 + H20
(propyl methanoate)

Question 4

How do we make an ester from acyl chloride?

Answer 4

Reacting with an alcohol —> ester + hydrogen chloride
Eg ethanoyl chloride + methanol
CH3COCl + CH3OH —> CH3COOCH3 + HCl
(methyl ethanoate)

Question 4

How do we make esters from acid anhydride?

Answer 4

React it with alcohol —> ester + carboxylic acid
(CH3CO)2O + CH3CH2OH —> CH3COOCH2CH3 + CH3COOH
(ethyl ethanoate and ethanoic acid)

Question 5

What can esters be hydrolysed by?

Answer 5

Hot AQUEOUS acid or hot AQUEOUS alkali

Question 6

What bond breaks when as ester is hydrolysed?

Answer 6

The sigma bond between the ester carbon and oxygen

Question 7

Describe the acid hydrolysis of water.

Answer 7

React ester with water in presence of HOT ACID (H2SO4), making carboxylic acid and alcohol

Question 8

What would happen in the acid hydrolysis of an ester? Give an example

Answer 8

Ester hydrolysed to carboxylic acid and alcohol. The acid doesn’t feature in the equation.
HCOOCH2CH2CH3 + H2O <—> HCOOH + CH3CH2CH2OH

Question 9

What would happen in the alkali hydrolysis od an ester? Give an example

Answer 9

Ester + metal hydroxide —> carboxylate salt + alcohol
E.g : NaOH(aq) and propyl methanoate
HCOOCH2CH2CH3 + NaOH —> HCOO-Na+ + CH3CH2CH2OH
salt = sodium methanoate