Alcohols (6) Esterification

Esterification is a reaction in organic chemistry that mirrors acid +base = salt + water in inorganic chemistry

Base      +  Acid         =      Salt    +    water

Alcohol + Organic acid  =  Ester    +   Water

Dr Carr’s Rescue Box: Naming Esters

This is where the examiner will make a sustained effort to

catch you out.

He knows that naming esters is tough for even the best candidates.

So how will we beat him? 

A bit of counter-intuitive thinking is needed from us. I mean thinking backwards!!

Here is an ester structural formula   CH₃CH₂COOCH₃ 

How do we name it?

First find the –COO- group. 

Note the alkyl groups either side, here we’ve an ethyl CH₃CH₂— and a methyl CH₃—

The ethyl is attached to the C of the COO group so that's the acid from which the ester’s named in this case 3 carbons or propanoic acid

The other alkyl group fronts up the name that is:

Methylpropanoate.

The conditions require the use of strong acid catalyst such as concentrated sulphuric acid (H₂SO₄) or hydrochloric acid (HCl).

The method is basically to heat the mixture of alcohol and organic acid and strong acid catalyst under reflux.

Then distill off the ester product.

Here is typical reaction:

Both these equations correctly show that the water forms from the hydrogen of the alcohol and the —O—H of the carboxyl group.

A less complicated method is illustrated here:

Once the mixture has been heated for a few minutes it can be poured into sodium carbonate solution to neutralise the acid catalyst leaving us to smell the ester.