Esters

Esters can be hydrolysed back to the acid and alcohol, by heating with an acid like dil. sulphuric acid. This is acid catalysed hydrolysis and is reversible. This reaction is just the reverse of esterification.
Soap is produced by saponification of triglycerides which are triesters found in oils and fats.
The name of the ester is derived from the parent acid and alcohol, for instance ethyl acetate (ethyl ethanoate) is derived from ethyl alcohol (ethanol) and acetic acid (ethanoic acid).
A convenient way to write the structure of an ester is to first write the structure of the acid as indicated in the name and then to replace the H of the acid group by the other group mentioned in the name.

Exercise

Esters can also be prepared from an acid chloride or acid anhydride instead of the acid, in fact, the acid derivatives are more reactive. In this case the small molecule eliminated during condensation would be .......................................................................
The acid chloride can be prepared from the acid by using …………………….................................
Acetic anhydride can be prepared from acetic acid by …………….................................................
Base catalysed hydrolysis of an ester is done by heating with a base like NaOH or KOH. This process is irreversible and results in ................... and ............. the acid itself can be generated by treating the .....……..... formed with Con. HCl. Base catalysed hydrolysis of an ester is saponification.
Write the structure of the following esters.
- Methyl formate
- Ethyl formate
- Methyl benzoate
- Ethyl benzoate
- Benzyl formate
- Benzyl benzoate
- Methyl anthranilate
- Methyl salicylate
- Phenyl acetate
- Phenyl salicylate

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