Dehydration of alcohol into alkene by concentration `H_2SO_4` involves which among the following reaction intermediate ?

Options

A. Free radical
B. Carbocation
C. Carbanion
D. Carbene

Answer

To solve the question regarding the dehydration of alcohol into alkene by concentrated H₂SO₄ and the reaction intermediate involved, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction**: The dehydration of alcohol involves the removal of a water molecule (H₂O) from the alcohol (RCH₂OH) to form an alkene (RCH=CH₂). This reaction is facilitated by concentrated sulfuric acid (H₂SO₄).

2. **Protonation of Alcohol**: The first step in the mechanism is the protonation of the alcohol. The lone pair of electrons on the oxygen atom of the alcohol (RCH₂OH) attacks a proton (H⁺) from the sulfuric acid. This forms an oxonium ion (RCH₂OH₂⁺).

3. **Formation of Carbocation**: The oxonium ion (RCH₂OH₂⁺) is unstable and undergoes a loss of water (H₂O) to form a carbocation (RCH₂⁺). This step is crucial as it generates the positively charged intermediate.

4. **Deprotonation to Form Alkene**: The carbocation (RCH₂⁺) can then lose a proton (H⁺) to form the alkene (RCH=CH₂). This step completes the dehydration process.

5. **Conclusion**: The reaction intermediate formed during the dehydration of alcohol by concentrated H₂SO₄ is a carbocation.

### Final Answer:
The reaction intermediate involved in the dehydration of alcohol into alkene by concentrated H₂SO₄ is a **carbocation**.