The mechanism of the Fischer esterification was controversial until 1938, when Irving Roberts and Harold Urey of Columbia University used isotopic labeling to follow the alcohol oxygen atom through the reaction. A catalytic amount of sulfuric acid was added to a mixture of 1 mole of acetic acid and 1 mole of special methanol containing the heavy 18Oisotope of oxygen. After a short period, the acid was neutralized to stop the reaction, and the components of the mixture were separated.

(a) Propose a mechanism for this reaction.
(b) Follow the labeled 18O atom through your mechanism, and show where it will be found in the products.
(c) The 18O isotope is not radioactive. Suggest how you could experimentally determine the amounts of 18O in the separated components of the mixture.

Transcribed Image Text:

H,so,