Dehydration of 2-butanol yield

Options

A. 1-butene
B. 2-butene
C. 2-butyne
D. Both (a) and (b)

Explanation

To solve the question regarding the dehydration of 2-butanol, we need to understand the process and the products formed during this reaction. Here’s a step-by-step breakdown of the dehydration of 2-butanol:

### Step 1: Identify the Structure of 2-butanol
2-butanol is a secondary alcohol with the following structure:
```
CH3-CH(OH)-CH2-CH3
```
In this structure, the hydroxyl (-OH) group is attached to the second carbon atom.

### Step 2: Understand the Dehydration Process
Dehydration of alcohols involves the elimination of a water molecule (H2O) from the alcohol. This typically occurs under acidic conditions (e.g., using sulfuric acid) and results in the formation of alkenes.

### Step 3: Mechanism of Dehydration
The dehydration of 2-butanol can proceed via the following mechanism:
1. Protonation of the hydroxyl group (-OH) to form a better leaving group (water).
2. Loss of water to form a carbocation intermediate.
3. Rearrangement (if applicable) and elimination of a proton to form the alkene.

### Step 4: Identify Possible Products
For 2-butanol, the dehydration can lead to two possible alkenes:
1. **1-butene**: Formed by elimination of a hydrogen from the adjacent carbon (C1) and the hydroxyl group from C2.
2. **2-butene**: Formed by elimination of a hydrogen from C3 and the hydroxyl group from C2.

### Step 5: Determine the Major Product
According to Zaitsev's rule, the more substituted alkene is generally the major product. In this case, 2-butene is more stable than 1-butene because it is more substituted (it has two alkyl groups attached to the double bond).

### Step 6: Conclusion
The dehydration of 2-butanol yields:
- 1-butene (Hofmann product)
- 2-butene (Zaitsev product)

Thus, both products can be formed, but 2-butene is the major product.

### Final Answer:
The dehydration of 2-butanol yields both 1-butene and 2-butene, with 2-butene being the major product.

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