Question

What alcohol should be used in the purification of ester Isopentyl propanoate (aka isoamyl propionate). And what mechanism does the reaction follow?

Answer 1

Isoamyl alcohol

Synthesis of Isopentyl propanoate or isopentyl acetate is done using an alcohol(Isoamyl alcohol or isopentyl alcohol) and (acidified) acetic acid .As the reaction proceeds the product and reactants are in equilibrium with each other. So to drive the formation of reaction ,by shifting the equilibrium in forward direction, an excess of the reactant either acetic acid or Isoamyl alcohol is added is used.(Le chatleir's principle is followed, in increasing the product by increasing reactant concentration.).The reactants are refluxed to increased the product yield (with excess reactants (Isoamyl alcohol or acetic acid).

The reaction is ficher esterification ,

..................................................(ACID/REFLUX).........................

CH3COOH + (CH3)2CHCH2CH2OHCH3COO-CH2CH2CH(CH3)2

The product so produced is a mixture of product and reactants in minor quantities.A separatory funnel is used to extract the organic layer from the aqueous layer (with acetic acid and sulphuric acid to be neutralized by using a mild base).

The organic layer that remains has the product ( Isopentyl propanoate) and alcohol isoamyl alcohol that are eventually separated by distillation.