Esterification Discussion

Isopentyl propionate, an ester, was synthesized using the method Fischer esterification, with the reagents 3-methyl butanol and propanoic acid.  Using 11 mmol of alcohol and 11 mmol of acid would theoretically yield 11 mmol of ester.  The carboxylic acid, propanoic acid, was used in slight excess (13 mmol) to ensure it reacts completely with the present alcohol.  The water formed in the reaction was removed from the solution using a distillation tube to ensure the reagents reacted completely.  Removing water would pull the reaction towards the products based on Le Chatelier’s principle.  Any remaining water was removed via backwashing and a drying agent, CaCl₂.  This procedure left a product expected to be isopentyl propionate, which was obtained in a 78% yield.  This could be due to inaccurate draining of the bottom layers from the tube.  Draining of the water back into the reaction could also account for the unreacted carboxylic acid stretch from 3535.52 cm^-1 to 3124.68 cm^-1 found in the IR results (attached at the end of this report).  The other impurities in the solution are not thought to be either of the reagents, acid or alcohol, due to the IR results.  The IR results are indicative of a C-H alkyl stretch at 2958.80 cm^-1.  There is a C=O ester stretch at 1739.79 cm^-1.  The third prominent peak, at approximately 1188.15 cm^-1, indicates there is a C-O stretch.  The isopentyl propionate had an odor characteristic of apple or pear when experimentally wafted.