Problem 73 - A Complete Resource Book in Chemistry for JEE Main

Question

Glucose reacts with bromine water to produce (a) glyceraldehyde (b) gluconic acid (c) saccharic acid (d) glutaric acid

Step-by-Step Solution

Answer

(b) Gluconic acid

Step 1: Understanding the Reaction

In this problem, we need to determine the product of the reaction between glucose and bromine water. Bromine water is a mild oxidizing agent, which can oxidize certain functional groups in organic compounds.

Step 2: Identifying the Functionality of Glucose

Glucose is an aldohexose, containing an aldehyde group at the first carbon. This aldehyde group is susceptible to oxidation, transforming into a carboxylic acid.

Step 3: Predicting the Product of Oxidation

When glucose undergoes mild oxidation with bromine water, the aldehyde group at the first carbon is oxidized to a carboxylic acid, resulting in the formation of gluconic acid.

Step 4: Conclusion Based on Reaction Specificity

The specific oxidation reaction converting an aldehyde group to a carboxylic acid, without affecting other functional groups in glucose, confirms that the product of the reaction is gluconic acid.

Key Concepts

Glucose Oxidation

Glucose is a simple sugar, or monosaccharide, which is crucial for the energy needs of living organisms. Its structure is characterized by an aldehyde group on its first carbon atom. During oxidation reactions, this aldehyde group is quite reactive. When glucose encounters an oxidizing agent, such as bromine water, a chemical reaction occurs which transforms the aldehyde into a carboxylic acid.
The oxidation of glucose typically targets the aldehyde group. This happens because the aldehyde is more reactive compared to other parts of the glucose molecule.

• The aldehyde group (–CHO) on the first carbon is oxidized to a carboxylic acid group (–COOH).
• This selective oxidation results in minimal changes to the glucose molecule, except for this specific transformation.

Thus, glucose oxidation via bromine water leads specifically to the production of gluconic acid, a mild transformation without breaking down the entire glucose molecule.

Bromine Water

Bromine water is a solution of bromine (Br8 8) in water, which acts as a mild oxidizing agent in chemical reactions. It is often used in organic chemistry to test for unsaturation and to cause certain functional group transformations.
When it comes to oxidizing substances like glucose, its mild nature ensures that only specific parts of the molecule are affected.

• Bromine water mainly affects functional groups capable of losing electrons easily, such as the aldehyde group in glucose.
• This specificity is crucial because it allows for targeted oxidation without impacting other stable parts of the molecule.

In the case of glucose, bromine water effectively converts the aldehyde group at the first carbon into a carboxylic acid, providing a clear pathway to obtain gluconic acid without affecting other hydroxyl groups on the structure.

Gluconic Acid

Gluconic acid is the result of the mild oxidation of glucose. Structurally, it is characterized by having the carboxylic acid group (–COOH) instead of the aldehyde group at the first carbon. The rest of the glucose molecule remains intact and unchanged.
This conversion from glucose to gluconic acid is an example of a selective oxidation reaction.

• Gluconic acid maintains the carbon backbone of glucose, ensuring it retains its initial molecular form, except for the functional group transformation.
• It is widely used in the food industry as a food additive for its mild acidity.

Understanding the transformation from glucose to gluconic acid is crucial as it reflects how specific chemical reactions can alter only particular aspects of a molecule, a key concept in organic chemistry.