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

(b) alkaline permanganate solution

Step 1: Understanding Baeyer's Reagent

Baeyer's reagent is a chemical reagent used in organic chemistry to test for the presence of unsaturated carbon-carbon bonds, such as alkenes and alkynes. It involves the use of permanganate ion, which reacts with these unsaturated compounds.

Step 2: Identifying the Correct State of Permanganate

Baeyer's reagent specifically refers to an alkaline solution of permanganate. This solution is used to oxidize double and triple bonds and is known for turning color from purple to brown when reacted with these unsaturated bonds.

Step 3: Evaluating the Options

Given the options: (a) acidified permanganate solution - used for different reactions, like oxidizing alcohols to carboxylic acids. (b) alkaline permanganate solution - correct for Baeyer's test on unsaturated bonds. (c) neutral permanganate solution - not typically referred to as Baeyer's reagent. (d) aqueous bromine solution - used for halogen addition reactions, not Baeyer's reagent.

Step 4: Conclusion

Based on the information that Baeyer's reagent is an alkaline solution of permanganate, the correct answer is: (b) alkaline permanganate solution.

Key Concepts

Chemical Reagents

Chemical reagents are substances or mixtures used to cause a chemical reaction or test if a reaction occurs. These reagents are pivotal in chemistry for synthesizing new compounds, testing hypotheses, and conducting experiments.
Reagents work by interacting with other substances to bring about a chemical change. Some common types include:

• Acids and bases: Used to adjust acidity or basicity.
• Solvents: Used to dissolve other substances.
• Oxidizing agents: Induce the oxidation of other substances, such as permanganate in Baeyer's reagent.

Baeyer's reagent is a special type of chemical reagent used specifically in organic chemistry. It helps identify the presence of unsaturated carbon-carbon bonds by utilizing the oxidizing ability of the permanganate ion. This reagent serves a specific purpose and must be prepared in an alkaline solution to perform its function effectively.

Organic Chemistry

Organic chemistry is a branch of chemistry that focuses on carbon-based compounds. It explores how carbon atoms bond with other atoms, forming complex molecules.
Given the vast number of possible carbon compounds, proteins, DNA, plastics, and countless everyday materials are studied within this field. Organic chemistry is vital for understanding biological processes, developing pharmaceuticals, and designing materials.
The introduction of chemical reagents, like Baeyer's reagent, allows chemists to manipulate and study these organic molecules. It helps in identifying specific types of bonds, like the unsaturated carbon-carbon bonds found in alkenes and alkynes. Thus, organic chemistry not only explains the structure and behavior of organic compounds but also tools like Baeyer's reagent enhance the study of these exciting and diverse molecules.

Unsaturated Carbon-Carbon Bonds

Unsaturated carbon-carbon bonds are found in organic molecules with double or triple bonds between carbon atoms. These bonds are termed unsaturated because they can potentially bond with additional atoms, such as hydrogen, indicating they hold more capacity for chemical reactions.

• Alkenes: Contain at least one carbon-carbon double bond.
• Alkynes: Contain at least one carbon-carbon triple bond.

These bonds are key focal points in organic reactions due to their reactive nature. When Baeyer's reagent is added to a substance with unsaturated bonds, it typically causes the purple-colored permanganate to oxidize these bonds, changing the solution to a brown color. This color shift acts as a visual indicator of the presence of unsaturated carbon bonds, highlighting why Baeyer's reagent is employed as a reliable test in organic chemistry laboratories.

Oxidation Reactions

Oxidation reactions involve the loss of electrons from a substance, often resulting in a change in its oxidation state. These reactions are fundamental in many chemical and biological processes. They are frequently paired with reduction reactions, collectively known as redox reactions.
Baeyer's reagent harnesses the power of oxidation reactions. When it encounters unsaturated carbon-carbon bonds, the permanganate ion in the reagent acts as an oxidizing agent. It reacts by adding oxygen to the bonds or removing hydrogen, causing a visual color change from purple to brown. This transformation confirms the occurrence of an oxidation reaction and helps distinguish compounds based on their saturation levels.
The significance of oxidation reactions is broad, influencing areas from energy production in burning fuels to metabolic processes in living organisms. In the laboratory, they provide crucial insights into structural features of organic compounds, driven forward by reagents like those used in Baeyer's test.