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 determine the reaction intermediate formed during the dehydration of alcohol into alkene using concentrated sulfuric acid (H₂SO₄), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reactants**:
- We start with an alcohol (RCH₂OH) and concentrated sulfuric acid (H₂SO₄). H₂SO₄ acts as a strong acid in this reaction.

2. **Protonation of Alcohol**:
- The first step involves the protonation of the alcohol. The hydroxyl group (-OH) of the alcohol can accept a proton (H⁺) from H₂SO₄, forming an oxonium ion (RCH₂OH₂⁺).
- This step can be represented as:
\[ RCH_2OH + H_2SO_4 \rightarrow RCH_2OH_2^+ + HSO_4^- \]

3. **Formation of Carbocation**:
- The oxonium ion (RCH₂OH₂⁺) is unstable and can lose a water molecule (H₂O) to form a carbocation (RCH₂⁺). This step is crucial as it leads to the formation of the carbocation intermediate.
- This can be represented as:
\[ RCH_2OH_2^+ \rightarrow RCH_2^+ + H_2O \]

4. **Deprotonation to Form Alkene**:
- The carbocation (RCH₂⁺) can then lose a proton (H⁺) to form an alkene (RCH=CH₂). This step completes the dehydration process.
- This can be represented as:
\[ RCH_2^+ \rightarrow RCH=CH_2 + H^+ \]

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

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