Question

STATEMENT-1: Glucose gives a reddish-brown precipitate with Fehling's solution. because STATEMENT-2: Reaction of glucose with Fehling's solution gives CuO and gluconic acid. (A) Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1 (B) Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1 (C) Statement- 1 is True, Statement- 2 is False (D) Statement- 1 is False, Statement- 2 is True

Short answer

Statement-1 is True, Statement-2 is False

Step-by-step solution

Examine Statement-1

Assess whether glucose forms a reddish-brown precipitate with Fehling's solution. Fehling's solution is used as a chemical test for reducing sugars like glucose. If glucose is a reducing sugar, it will react with the copper(II) complex in Fehling's solution to produce a red-brown precipitate of copper(I) oxide (Cu2O), not CuO as mentioned in Statement-2.

Examine Statement-2

Evaluate the chemical reaction of glucose with Fehling's solution. The statement should indicate the production of copper(I) oxide (Cu2O) and an organic acid (gluconic acid) as the products of this reaction. However, the statement incorrectly indicates the production of CuO, which is copper(II) oxide.

Determine the Relationship

Determine if Statement-2 properly explains Statement-1. Since Statement-2 contains an error in the chemical formula of the precipitate, it cannot be a correct explanation for Statement-1.

Select the Correct Option

Based on the analysis of the statements, choose the correct option among (A), (B), (C), and (D).

Key concepts

Reducing Sugars

Reducing sugars are a classification of carbohydrates that are capable of acting as a reducing agent due to their free aldehyde or ketone functional groups in their molecular structure. Glucose is one such example with an aldehyde group, which allows it to participate in oxidation-reduction reactions. In these reactions, the sugar molecule donates electrons to another compound—typically a metal ion—thus reducing it.

The Fehling's solution test is a classic chemical assay used to detect the presence of reducing sugars. It contains copper(II) sulfate mixed with potassium sodium tartrate in an alkaline medium. When a reducing sugar like glucose is warmed with Fehling's solution, it reduces the blue Cu(II) ions to red Cu(I) oxide, which appears as a reddish-brown precipitate. This test not only confirms the presence of a reducing sugar but also distinguishes them from non-reducing sugars, which do not react with Fehling's solution.

Glucose Chemical Reactions

Glucose, a monosaccharide with the formula C₆H₁₂O₆, undergoes various chemical reactions that are fundamental to organic chemistry. One of the key reactions for testing the presence of glucose is its interaction with Fehling's solution, as mentioned earlier.

It's crucial to accurately represent the products of this reaction. Upon reacting with Fehling's solution, glucose is oxidized to gluconic acid, while the Cu(II) ions in the solution are reduced to Cu(I) oxide, which is Cu₂O, not CuO as sometimes incorrectly cited. This nuance is important for a correct understanding of the redox chemistry involved between glucose and Fehling's solution. Misstating the product as CuO rather than Cu₂O can lead to confusion when mastering the chemistry of carbohydrates.

Understanding these reactions is crucial for students, especially those preparing for competitive exams like the JEE Advanced, where details in chemical reactions can be critical for solving complex problems.

Organic Chemistry in JEE Advanced

Organic chemistry comprises a significant portion of the JEE Advanced syllabus, which demands a deep understanding of mechanisms, reactions, and the properties of organic compounds. The Fehling's test for reducing sugars like glucose is a fine illustration of the practical application of organic reaction mechanisms.

In preparation for JEE Advanced, aspirants must be adept at distinguishing between similar-sounding concepts and writing precise chemical equations, a skill that can impact their performance significantly in the exam. For instance, knowing the difference between CuO and Cu₂O is crucial since incorrect representation can lead to wrong conclusions and loss of marks in the exam.

Moreover, integrating concepts such as the ability of particular functional groups to undergo redox reactions, as exemplified by the Fehling's solution test, helps in solving a complex array of problems posed in the exam. Taking organic chemistry beyond rote learning and into the realm of practical and analytical thinking forms the core of cracking competitive exams like the JEE Advanced.