Question

1. If you look at a reaction equation for a Fischer esterification reaction, you cannot tell where the oxygen comes from (acid or alcohol). Knowing the mechanism of this reaction, devise an experiment using O18, to help prove unequivocally where the oxygen comes from. 2 The Fischer Esterification is highly reversible and the products are only, slightly favored. State two procedures you did to help drive the reaction to the ester. 3. A student forgot to remove their silica gel beads before distillation of ester product. After distillation, his product was cloudy, indicating it was wet. Why

Answer 1

Answer:

Explained

Explanation:

In the experiment, an (18)O-labelled alcohol R('18)OH is used with normal unlabeled carboxylic acid RC(16)O2H:

The esterification reaction is:  

(note: the bracketed values are atomic masses)

RC(16)O_2H + R'(18)OH => RC16O18OR' + H_2(16)O

Since the alcohol is the nucleophile in this nucleophilic substitution reaction, it adds to the carbonyl group of the carboxylic acid and the (18)O atom becomes incorporated into the ester product, while the (16)OH group of the carboxylic acid is expelled as H_2(16)O.

By using mass spectroscopy to measure the mass of the ester and water products, it can be shown that each ester molecule contains one (18)O atom and one (16)O atom, while the water molecules contains only (16)O atoms.

This would prove unequivocally that the ester contains one O atom from the carboxylic acid and one O atom from the alcohol, while the water contains only O atoms from the carboxylic acid.