Baeyer's reagent decolourises which of the following :

Options

A. Alkane
B. Alkene only
C. Alkene and alkyne both
D. Benzene

Answer

To solve the question regarding which compounds Baeyer's reagent decolorizes, we can follow these steps:

### Step 1: Understand Baeyer's Reagent
Baeyer's reagent is an alkaline solution of potassium permanganate (KMnO4). It is commonly used in organic chemistry to test for the presence of unsaturation in organic compounds.

### Step 2: Identify the Color of Baeyer's Reagent
Baeyer's reagent has a characteristic pink color due to the presence of permanganate ions (MnO4^-).

### Step 3: Determine the Reaction with Unsaturated Compounds
When Baeyer's reagent reacts with unsaturated hydrocarbons (alkenes and alkynes), it undergoes a reduction reaction. The permanganate ions are reduced, resulting in the decolorization of the pink color of the reagent.

### Step 4: Define Unsaturated Hydrocarbons
Unsaturated hydrocarbons are compounds that contain at least one double bond (alkenes) or one triple bond (alkynes).

### Step 5: Conclude the Answer
Since Baeyer's reagent decolorizes in the presence of unsaturated hydrocarbons, the correct answer to the question is that Baeyer's reagent decolorizes both alkenes and alkynes.

### Final Answer
The correct options that Baeyer's reagent decolorizes are **alkenes and alkynes**.

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