Formation of Penta-Acetate from Glucose and Acetic Anhydride

Glucose is a monosaccharide, which is a simple sugar. Acetic anhydride is a colorless liquid that is used as a solvent and reagent in organic chemistry. When glucose reacts with acetic anhydride, it forms a penta-acetate. The reaction is shown below:

Glucose + 5 Acetic Anhydride → Penta-Acetate + 5 Acetic Acid

The penta-acetate is a crystalline solid that is soluble in organic solvents. It is used in the synthesis of various organic compounds.

Mechanism of Reaction

The reaction between glucose and acetic anhydride proceeds via a nucleophilic substitution mechanism. The steps involved in the mechanism are as follows:

Step 1: Formation of Acetyl Glucose

In the first step, acetic anhydride reacts with glucose to form an acetyl glucose intermediate. This reaction is catalyzed by acid.

Glucose + Acetic Anhydride + Acid → Acetyl Glucose + Acetic Acid

Step 2: Formation of Di-Acetyl Glucose

In the second step, another molecule of acetic anhydride reacts with the acetyl glucose intermediate to form a di-acetyl glucose intermediate.

Acetyl Glucose + Acetic Anhydride → Di-Acetyl Glucose + Acetic Acid

Step 3: Formation of Tri-Acetyl Glucose

In the third step, another molecule of acetic anhydride reacts with the di-acetyl glucose intermediate to form a tri-acetyl glucose intermediate.

Di-Acetyl Glucose + Acetic Anhydride → Tri-Acetyl Glucose + Acetic Acid

Step 4: Formation of Tetra-Acetyl Glucose

In the fourth step, another molecule of acetic anhydride reacts with the tri-acetyl glucose intermediate to form a tetra-acetyl glucose intermediate.

Tri-Acetyl Glucose + Acetic Anhydride → Tetra-Acetyl Glucose + Acetic Acid

Step 5: Formation of Penta-Acetyl Glucose

In the final step, another molecule of acetic anhydride reacts with the tetra-acetyl glucose intermediate to form a penta-acetyl glucose intermediate.

Tetra-Acetyl Glucose + Acetic Anhydride → Penta-Acetyl Glucose + Acetic Acid

Thus, the reaction between glucose and acetic anhydride proceeds through a series of steps to form a penta-acetate.