The mechanism of the Fischer esterification was controversial until 1938, when IrvingRoberts and Harold Urey of Columbia University used isotopic labeling to follow thealcohol oxygen atom through the reaction. A catalytic amount of sulfuric acid was addedto a mixture of 1 mole of acetic acid and 1 mole of special methanol containing the heavy18O isotope of oxygen. After a short period, the acid was neutralized to stop the reaction,and the components of the mixture were separated.H2SO4OCH3 C O H CH3 O H CH3 C O CH3 H2OO18 + +(a) Propose a mechanism for this reaction.(b) Follow the labeled 18O atom through your mechanism, and show where it is found inthe products.(c) The 18O isotope is not radioactive. Suggest how you could experimentally determinethe amounts of 18O in the separated components of the mixture
Catalysis and Enzymatic Reactions
Catalysis is the kind of chemical reaction in which the rate (speed) of a reaction is enhanced by the catalyst which is not consumed during the process of reaction and afterward it is removed when the catalyst is not used to make up the impurity in the product. The enzymatic reaction is the reaction that is catalyzed via enzymes.
Lock And Key Model
The lock-and-key model is used to describe the catalytic enzyme activity, based on the interaction between enzyme and substrate. This model considers the lock as an enzyme and the key as a substrate to explain this model. The concept of how a unique distinct key only can have the access to open a particular lock resembles how the specific substrate can only fit into the particular active site of the enzyme. This is significant in understanding the intermolecular interaction between proteins and plays a vital role in drug interaction.
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
18O isotope of oxygen. After a short period, the acid was neutralized to stop the reaction,
and the components of the mixture were separated.
H2SO4
O
CH3 C O H CH3 O H CH3 C O CH3 H2O
O
18 + +
(a) Propose a mechanism for this reaction.
(b) Follow the labeled 18O atom through your mechanism, and show where it is 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
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