Question

Draw and name the structures of each ester in the table

Acid	Alcohol	Essence
1 g Salicylic acid	Methanol	Wintergreen
3 mL Acetic acid	1-Octanol	Orange
2 mL Butyric acid	Ethanol	Pineapple
2 mL Butyric acid	Methanol	Apple
2 mL Butyric acid	Pentanol (amyl alcohol)	Apricot
2m L Acetic acid	Pentanol (amyl alcohol)	Banana

As mentioned in the introduction, when esters are to be isolated from the equilibrium mixture use is made of the volatility of the ester, allowing it to be distilled easily from the other reagents. To illustrate this, look up the boiling point of the ester n-propyl acetate (1-propyl ethanoate) and of its constituent alcohols 1-propanol and organic acid, ethanoic acid.

Give the order of distillation and explain your order.

Write reactions for the 2 esterification reactions you performed:

Ordinarily, esterification reactions come to equilibrium before the full theoretical yield of ester is realized. Aside from distillation discussed earlier, how might one experimentally shift the equilibrium of the esterification reaction so that a larger amount of ester might be isolated?

Answer 1

The boiling point of the ester, n-propyl acetate has a boiling point of 102^oC and of its constituent alcohols 1-propanol has 97^oC and organic acid, ethanoic acid has 118^oC. Therefore, the order of distillation should be the one with the lower boiling point followed by the next lower boiling point and finally the higher boiling point. Accordingly, 1-propanol comes first followed by n-propyl acetate and lastly ethanoic acid.

Reactions for the 2 esterification reactions:

One can experimentally shift the equilibrium of the esterification reaction so that a larger amount of ester might be isolated. The yield of ester can be improved by increasing the concentration of one of the reactants (either the alcohol or the carboxylic acid).
By Le Chatelier's Principle an excess of one reactant will drive the reaction to the right, increasing the production of ester, and therefore increasing the yield of ester.