Esterification reaction

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• published: 08 May 2015
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Esterification is the chemical process for making esters, which are compounds of the chemical structure R-COOR', where R and R' are either alkyl or aryl groups.Glacial acetic acid is a trivial name for water-free (anhydrous) acetic acid. Similar to the German name Eisessig (ice-vinegar), the name comes from the ice-like crystals that form slightly below room temperature at 16.6 °C (61.9 °F) (the presence of 0.1% water lowers its melting point by 0.2 °C).[11]Fischer esterification is an example of nucleophilic acyl substitution based on the electrophilicity of the carbonyl carbon and the nucleophilicity of an alcohol. However, carboxylic acids tend to be less reactive than esters as electrophiles. Additionally, in dilute neutral solutions they tend to be deprotonated anions (and thus unreactive as electrophiles). Though very kinetically SLOW without any catalysts (most esters are metastable), pure esters will tend to spontaneously hydrolyse in the presence of water, so when carried out "unaided", high yields for this reaction is quite unfavourable. Several steps can be taken to turn this "unfavourable" reaction into a favourable one.[citation needed] The reaction mechanism for this reaction has several steps: Proton transfer from acid catalyst to carbonyl oxygen increases electrophilicity of carbonyl carbon. The carbonyl carbon is then attacked by the nucleophilic oxygen atom of the alcohol Proton transfer from the oxonium ion to a second molecule of the alcohol gives an activated complex Protonation of one of the hydroxyl groups of the activated complex gives a new oxonium ion. Loss of water from this oxonium ion and subsequent deprotonation gives the ester. A generic mechanism for an acid Fischer esterification is shown below.