Chemistry A2 - Esters

Question 1

What is the function group of esters?

Answer 1

-COO-

Question 2

How do you name an ester?

Answer 2

• Remove the oic acid suffix from the parent carboxylic acid and replace it with -oate
• The alkyl chain attached to the oxygen atom of the -COO- is then added as the first word in the name

Question 3

Why are ester names confusing?

Answer 3

They are written backwards from the way the are drawn

Question 4

What is esterification and how does it work?

Answer 4

Esterification is the formation of an ester and they are prepared from the condensation reaction between a carboxylic acid and an alcohol with concentrated sulphuric acid as a catalyst

Question 5

Why is esterification an example of a condensation reaction?

Answer 5

Water is eliminated from the acid and the alcohol reacting together

Question 6

What is the less common way in which esterification can occur?

Answer 6

The reaction of acid anhydrides with alcohols at room temperature

Question 7

What are acid anhydrides and how are they formed?

Answer 7

They are derivates of carboxylic acids and formed by the substitution of the -OH group by an alkanoate

Question 8

How are acid anhydrides named?

Answer 8

• By identifying the parent hydrocarbon chain and adding the suffix -oic anhydride
  OR
• Removing the -oic acid from a carboxylic acid and adding -oic anhydride

Question 9

How are esters hydrolysed and what do they form?

Answer 9

They are hydrolysed with dilute acid/alkali with heat and they reform the carboxylic acid

Question 10

What happens when an ester is heated under reflux with a dilute acid?

Answer 10

An equilibrium mixture is established as the mixture is reversible

Question 11

What happens when an ester is heated under reflux with a dilute alkali?

Answer 11

It is a reversible reaction and so sodium carboxylate salt is formed which needs further acidification to turn into a carboxylic acid