Problem 41 - A Complete Resource Book in Chemistry for JEE Main

Question

Baeyer's reagent is (a) acidified permanganate solution (b) alkaline permanganate solution (c) neutral permanganate solution (d) aqueous bromine solution

Step-by-Step Solution

Answer

Baeyer's reagent is (b) alkaline permanganate solution.

Step 1: Understanding Baeyer's Reagent

Baeyer's reagent is a term used in organic chemistry to refer to a specific oxidizing agent. It is often used in the qualification of unsaturated compounds.

Step 2: Identify the Composition of Baeyer's Reagent

Baeyer's reagent typically consists of a dilute solution of potassium permanganate in an alkaline medium. This reagent is used as a qualitative test to detect the presence of carbon-carbon double bonds (alkenes) in a solution.

Step 3: Match with the Options

Given the choices, identify which option corresponds to the alkaline permanganate solution: (a) acidified permanganate solution (b) alkaline permanganate solution (c) neutral permanganate solution (d) aqueous bromine solution. Option (b) matches, as it correctly describes Baeyer's reagent.

Key Concepts

Understanding Oxidizing Agents

An oxidizing agent is a substance that can accept electrons during a chemical reaction. Oxidizing agents play a crucial role in redox reactions, where they cause another substance to lose electrons, also known as oxidation.
An oxidizing agent itself gets reduced as it gains electrons. This makes them essential in various chemical processes, including organic reactions and industrial applications.

• They help in breaking down complex substances during chemical reactions.
• Used in processes such as cleaning, bleaching, and disinfecting.

In organic chemistry, oxidizing agents are often used to add oxygen or remove hydrogen from molecules, making them fundamental tools in the synthesis and modification of organic compounds.

Role of Potassium Permanganate

Potassium permanganate (\( KMnO_4 \)) is a powerful oxidizing agent commonly used in chemical reactions, both in laboratories and industries. It is a deep purple compound that, when dissolved in water, forms a strikingly colored solution.
Potassium permanganate is versatile and can be adjusted to work under different conditions:

• In acidic solutions, it can oxidize various substances including alcohols and aldehydes.
• In neutral or alkaline solutions, like Baeyer's reagent, it is often employed to test for unsaturation in organic compounds.

Its ability to oxidize a wide range of organic and inorganic substances makes it invaluable for qualitative analysis as well as for purification and treatment processes. In Baeyer's reagent, it specifically targets carbon-carbon double bonds, a characteristic explained in the following section.

Detecting Carbon-Carbon Double Bonds

One of the key uses of Baeyer's reagent, which is prepared using potassium permanganate, is to detect the presence of carbon-carbon double bonds in a compound. These bonds are indicative of alkenes or unsaturated compounds.
Here's how the detection process works:

• When the potassium permanganate reacts with a double-bonded compound, it causes oxidation of the double bond.
• This reaction results in the breaking of the double bond and forms a glycol, a molecule containing two alcohol groups.
• The color of the permanganate solution changes from purple to brown, indicating that a reaction has taken place.

This color change serves as a simple visual cue for the presence of double bonds in the tested molecule, making it a practical and efficient method for unsaturation testing in organic chemistry. This characteristic transformation facilitates the identification of alkenes and enhances understanding of the molecular structure and reactivity.