Posted by: Mark Foreman | January 21, 2012

Ester formation

I think the next key reaction of the carboxylic acids (and their derivatives) is the reaction which converts the carboxylic acid into an ester. This is an example of a substitution reaction where one group is replaced with another group. The first method which we will look at is the Fisher ester synthesis. This is the reaction of a carboxylic acid and an alcohol which is done with a strong (mineral) acid catalyst.

Here is the reaction in all its glory, but the key thing to observe is that protonation occurs of the carboxylic acid. This makes the carboxylic acid more electrophilic thus encouraging the alcohol to attack as a nucleophile. It is important to understand that the carboxylic acid must be protonated first.

Just in case you thought that the formation of esters is not an important matter, here is the short story of how I converted a bar of soap into esters to allow me to use gas chromatography on it. I think that the use of chromatography and spectrscopy to follow reactions is very important in chemistry, here is another story which shows how gas chromatography can be used to prove something which is in many text books about the SN2 reaction.

We will get onto alkyl halides, alkenes and aromatic rings soon, aromatic rings are very important in chemistry. Here is a nice picture which relates to aromatic rings.


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