Practicing Success

Target Exam

CUET

Subject

Chemistry

Chapter

Organic: Biomolecules

Question:

Which of the following is true?

(A) Sucrose is a non-reducing agent

(B) Glucose is oxidized by bromine water

(C) Glucose rotates plane-polarized light in a clockwise direction

(D) Fructose is oxidized by bromine water

Select the correct answer during the coded given below:

Options:

(A), (B), (C)

(A), (B) only

(B), (C) only

(A), (D) only

Correct Answer:

(A), (B), (C)

Explanation:

The correct answer is option 1. (A), (B) and (C)

Let us analyze each statement in detail to confirm the true ones:

(A) Sucrose is a non-reducing agent:

The statement is true. Sucrose is a disaccharide made up of glucose and fructose linked via a glycosidic bond. In this bond, the anomeric carbons of both glucose and fructose are involved in the linkage, leaving no free aldehyde or ketone group to participate in redox reactions. Therefore, sucrose does not react with Tollen's reagent or Fehling's solution and is considered a non-reducing sugar.

(B) Glucose is oxidized by bromine water:

The statement is true. Glucose is a reducing sugar because it contains a free aldehyde group. Bromine water, which is a mild oxidizing agent, oxidizes the aldehyde group of glucose to a carboxylic acid, converting glucose to gluconic acid. This reaction occurs as follows:

\(C_6H_{12}O_6 (\text{Glucose}) + Br_2 + H_2O \rightarrow C_6H_{12}O_7 (\text{Gluconic acid}) + 2HBr\)

(C) Glucose rotates plane-polarized light in a clockwise direction:

The statement is true. D-Glucose is dextrorotatory, meaning it rotates plane-polarized light to the right (clockwise). This is a characteristic property of the D-isomer of glucose.

(D) Fructose is oxidized by bromine water:

The statement is false. Fructose is a ketose sugar and generally, bromine water does not oxidize ketones under mild conditions. Instead, strong oxidizing agents are required to oxidize ketones. Bromine water is effective for oxidizing aldehydes but not ketones.

Combining these analyses, the correct statements are:

(A) Sucrose is a non-reducing agent.

(B) Glucose is oxidized by bromine water.

(C) Glucose rotates plane-polarized light in a clockwise direction.

Therefore, the correct answer is option 1. (A), (B), (C)