6.1.10: Esters Flashcards
Which functional group do esters contain?
R-COO-R’
What is esterification?
A chemical reaction used to make an ester.
What are the two main ways used to make an ester?
Carboxylic acid with alcohol
Acid anhydride ith alcohol.
Describe how you would make a small ester with carboxylic acid with alcohol. Also, describe the rate.
- An alcohol and carboxylic acid are heated gently in the presence of a sulphuric acid catalyst.
- Esterification is a reversible reaction and has a slow rate of reaction.
How can an ester be separated from the reaction mixture and why does this have to happen quickly?
(Carboxylic acid with alcohol)
As the ester is volatile, with the lowest boiling point of the chemicals, it can be separated from the reaction mixture using distillation.
-The separation has to happen quickly to prevent the reverse reaction occurring.
How would you prepare a large ester with alcohol and carboxylic acid and how would it be separated?
- The reaction mixture would need to be heated under reflux until equilibrium has been established.
- The ester can be separated using fractional distillation.
Why is esterification using a phenol and carboxylic acid not suitable for a phenol or its derivatives?
The rate of reaction is too slow.
What is an acid anhydride?
An acid derivative that is more reactive than similar carboxylic acid.
how is an acid anhydride made?
By the removal of a molecule of water from two carboxylic acid molecules.
How can acid anhydrides be used to make an ester?
Acid anhydrides can be reacted with an alcohol, including phenol and its derivatives, to make an ester.
Why does esterification using an acid anhydride and an alcohol have a higher yield?
Because this method of ester production is not reversible.
The rate of reaction of esterification using an acid anhydride and an alcohol is slow. How can this be increased?
By gently warming the reaction mixture.
What is hydrolysis?
A chemical reaction where water breaks down another product.
How can an ester become an alcohol and what is the other product?
- Esters can undergo hydrolysis to form an alcohol; It is the reverse reaction of esterification.
- By varying the conditions, either a carboxylic acid or carboxylate salts are formed as the other product.
When esters are refluxed with a catalyst of hot aqueous acids, such as dilute H2SO4 or HCl, what will happen?
The ester will decompose reversibly into an alcohol and a carboxylic acid.
