Q2. - Organic Chemistry

Question

Question: During the metabolism of glucose, glyceraldehyde 3-phosphate is converted to dihydroxyacetone phosphate by a process that involves two keto-enol tautomerizations. Draw a stepwise mechanism for this reaction in the presence of acid.

Step-by-Step Solution

Answer

Answer

The stepwise mechanism for the conversion of glyceraldehyde 3-phosphate to dihydroxyacetone in the presence of an acid is shown below.

Step 1: Definition of tautomers

Tautomers are structural isomers of organic compounds that undergo interconversion in an acidic or a basic medium in the presence of water. The process of conversion of one kind of tautomer into another is known as tautomerization. One such example is keto-enol tautomers.

 

Step 2: Keto-enol tautomerism

Enol and keto forms are tautomers that are present in the carbonyl group, and their difference lies in the position of a double bond and a proton. A ketone has a C=O bond and an additional C-H bond, while an enol has C-OH and C=C bonds. They are constitutional isomers that are found to be in equilibrium with each other.

Step 3: Tautomerization mechanism

The tautomerization process is shown for the conversion of glyceraldehyde 3-phosphate to dihydroxyacetone in the presence of an acid.

                           Formation of diyrxy acetone phosphate

 

Representation of the conversion of glyceraldehyde 3-phosphate to dihydroxyacetone in the presence of an acid

 

Based on the explanations, the stepwise mechanism for the conversion of glyceraldehyde 3-phosphate to dihydroxyacetone in the presence of an acid is shown below.

Representation of the conversion of glyceraldehyde 3-phosphate to dihydroxyacetone in the presence of an acid