Acid catalysed dehydration of 2-pentanol would give

Options

A. 1-pentene as a major product
B. cis 2-pentene as a major product
C. trans-2-pentene as a major product
D. cis- and trans - 2-pentene in equal amount.

Answer

To determine the major product of the acid-catalyzed dehydration of 2-pentanol, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactant**:
The reactant is 2-pentanol, which has the following structure:
\[ \text{CH}_3\text{CH(OH)CH}_2\text{CH}_2\text{CH}_3 \]

2. **Protonation of Alcohol**:
In the presence of an acid (H⁺), the hydroxyl group (-OH) of 2-pentanol gets protonated, forming a protonated alcohol:
\[ \text{CH}_3\text{CH(OH}_2^+\text{)CH}_2\text{CH}_2\text{CH}_3 \]

3. **Formation of Carbocation**:
The protonated alcohol can lose a water molecule (H₂O) to form a carbocation. The loss of water can occur at the carbon adjacent to the hydroxyl group, leading to the formation of a secondary carbocation:
\[ \text{CH}_3\text{C}^+\text{HCH}_2\text{CH}_2\text{CH}_3 \]

4. **Carbocation Rearrangement**:
The formed carbocation can rearrange to form a more stable carbocation if possible. In this case, there is no rearrangement needed as the secondary carbocation is already stable.

5. **Deprotonation to Form Alkene**:
The carbocation can lose a proton (H⁺) to form an alkene. There are two possible alkenes that can form: cis-2-pentene and trans-2-pentene. The reaction can proceed to form both isomers.

6. **Stability of Alkenes**:
Between cis-2-pentene and trans-2-pentene, trans-2-pentene is more stable due to less steric hindrance between the larger alkyl groups.

7. **Final Products**:
Therefore, the major product of the acid-catalyzed dehydration of 2-pentanol is trans-2-pentene, while cis-2-pentene is the minor product.

### Conclusion:
The major product of the acid-catalyzed dehydration of 2-pentanol is **trans-2-pentene**.

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