Esters Flashcards
What is an ester?
A homologous series of organic molecules which has 2 carbon chains connected by O=C-O-C
Naming esters
2 parts to name: _yl _anoate
The prefixes include the branching and any other functional groups
The yl part is from the alcohol and includes the chain after the O which does not have the C=O
The oate is from the carboxylic acid/acyl chloride and before the O and does have the C=O
How do we form an ester?
Carboxylic acid or acyl chloride + alcohol
Uses of esters
They have fruity smells so used for fragrances in foods and cosmetics
Esterification
Forming an ester with Alcohol + acyl chloride/carboxylic acid
Heated under reflux with an acid catalyst
What type of reaction is esterification?
Condensation reaction because a molecule of water is removed and joins 2 molecules together to form a large molecule
A reversible reaction
Because esterifictaion is a reversible reaction….
We need to distil off the ester product as it’s made to separated
How do we separate the ester from the reaction mixture of esterification?
Obtain the distillate
Remove carboxylic acid by adding sodium carbonate to neutralise the acid and stop the reaction + removes H+ ion from the sulfuric acid catalyst
Separate organic ester product from the aqueous layer because organic layer formed on top of
Reactions of esters
Acid hydrolysis which is a reverse of esterification AND a reversible reaction
Alkali hydrolysis
Like hydrolysis of nitriles to make a carboxylic acid
Acid hydrolysis of ester
Adding water to break the ester link and form alcohol + acyl chloride/ carboxylic acid
Under reflux and H+ acid catalyst
Conditions for acid hydrolysis of ester
Dilute acid conditions (H+ ion written above reversible reaction arrow)
Reflux
Lots of water
Alkali hydrolysis
Ester + OH- forms carboxylate ion and alcohol
Heated under reflux with aqueous alkali
Wash through with dilute acid to proton ate carboxylate ion
