Esters Flashcards
Reactions you need to know
What is Fischer esterification
The reaction between a carboxylic acid and water in the presence of an acid catalyst
What is the mechanism for Fischer esterification
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How can efficiency of Fischer esterification be improved
The entire reaction is an equilibrium, so the removal of water using Dean Stark apparatus can push equilibrium towards the products
Outline base catalysed esterification
Uses an alcohol and usually an acid anhydride (can also by an acyl chloride). Pyridine is usually used as the base and the intermediate salt is more reactive than the start material.
Mechanism for the base catalysed esterification using pyridine
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How many equivalents of base are required for the base catalysed esterification
1 equivalent to neutralise the acid by-product
Outline ester hydrolysis under acidic conditions
Mechanism is the reverse of the Fischer reaction. xs water pushes equilibrium towards the product. The acid increases electrophilicity of the C=O bond and improved the leaving group ability of OH
Outline ester hydrolysis under basic conditions including its colloquial name
Also called saponification. NaOH is used (1 equiv) and the product is a sodium salt of the carboxylic acid.
Main difference between ester hydrolysis under basic relative to acidic conditions
The product under basic conditions is a salt that is not electrophilic and hence cannot be attacked by a nucleophile. This makes the reaction irreversible
What is transesterification
Exchange of the organic functional group of an ester with that of the organic functional group of an alcohol to produce two different esters and alcohols
Draw transesterification mechanisms under acidic and basic conditions
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