Question

When glucose is oxidized with nitric acid, the compound formed is

• A. Gluconic acid
• B. n-Hexanoic acid
• C. Saccharic acid
• D. Cyanohydrin

Hint:

In carbohydrate chemistry, oxidation reactions can convert glucose into different acids. Mild oxidation forms gluconic acid, while strong oxidation (using nitric acid) forms saccharic acid.

Answer 1

The Correct Option is C

When glucose is oxidized with nitric acid, saccharic acid is formed. This reaction involves the oxidation of both the aldehyde group at the C1 position and the primary alcohol group at the C6 position of the glucose molecule, resulting in the formation of a dicarboxylic acid known as saccharic acid.

Explanation:

1. Glucose is a monosaccharide containing an aldehyde group, making it an aldose.

2. When oxidized with a strong oxidizing agent like nitric acid (HNO₃), both the aldehyde (-CHO) group and the primary alcohol (-CH₂OH) are converted to carboxyl (-COOH) groups.

3. The oxidation of the aldehyde group at C1 and the primary alcohol group at C6 of glucose produces a dicarboxylic acid, specifically saccharic acid (also known as glucaric acid).

This transformation is significant in carbohydrate chemistry as it demonstrates the ability of strong oxidizers to convert aldoses into dicarboxylic acids by oxidizing the terminal functional groups.

Answer 2

Step 1: Understanding the oxidation of glucose 

Glucose (C₆H₁₂O₆) is a monosaccharide that contains both an aldehyde (-CHO) group and hydroxyl (-OH) groups. When glucose is treated with nitric acid (HNO₃), it undergoes oxidation.

Step 2: Oxidation process

- Mild oxidation: If glucose is oxidized using a mild oxidizing agent such as bromine water (Br₂), only the aldehyde group (-CHO) is oxidized to a carboxyl group (-COOH), forming gluconic acid.

- Strong oxidation: When glucose is oxidized using strong oxidizing agents such as nitric acid (HNO₃), both the aldehyde (-CHO) group and the terminal primary alcohol (-CH₂OH) group are oxidized to carboxyl (-COOH) groups, forming saccharic acid (also known as glucaric acid).

Step 3: Examining the given options

- Option 1: Gluconic acid → Formed under mild oxidation conditions.
- Option 2: n-Hexanoic acid → A fatty acid, not related to glucose oxidation.
- Option 3: Saccharic acid → Correct answer; formed when glucose is oxidized with nitric acid.
- Option 4: Cyanohydrin → Formed in reactions involving hydrogen cyanide (HCN), not nitric acid oxidation.

Step 4: Conclusion

Since nitric acid oxidizes both the aldehyde and primary alcohol groups of glucose to carboxyl (-COOH) groups, the correct answer is saccharic acid.