The major product of the following reaction is :
`{:(CH_(3)CH_(2)CH-CH_(2) ),(" |"" |"),(" "Br" " Br):}` `underset(underset("in liq" NH_(3))(II. NaNH_(2)))overset("I. KOH alc")rarr`

Options

A. `CH_(3)CH_(2)C -= CH`
B. `CH_(3)CH = C = CH_(2)`
C. `{:(CH_(3)CH_(2)CH-CH_(2)),(" |"" |"),(" "NH_(2)" "NH_(2)):}`
D. `CH_(3)CH=CHCH_(2)NH_(2)`

Explanation

To solve the given reaction step-by-step, we will analyze the reactants and the reagents used in the reaction. The reactant is 1,2-dibromobutane, and we will go through the elimination and substitution processes to find the major product.

### Step 1: Identify the Reactant
The reactant is 1,2-dibromobutane, which can be represented as:
```
CH3-CH2-CH-CH2
| |
Br Br
```

### Step 2: First Step - Dehydrohalogenation with KOH (alc)
In the first step, we treat the reactant with alcoholic KOH, which provides hydroxide ions (OH⁻). This will lead to a dehydrohalogenation reaction, where one of the bromine atoms and a hydrogen atom are eliminated to form a double bond.

- The hydroxide ion will preferentially remove the less hindered hydrogen atom (which is attached to the carbon adjacent to the bromine).
- The elimination will result in the formation of a double bond between the second and third carbon atoms.

The product after this step will be:
```
CH3-CH2-CH=CH2
|
Br
```
This product is 3-bromobutene.

### Step 3: Second Step - Reaction with NaNH2 in Liquid NH3
In the second step, we introduce sodium amide (NaNH2) in liquid ammonia (NH3). Sodium amide is a strong base and will deprotonate the hydrogen atom adjacent to the double bond, leading to the formation of a carbon anion.

- The carbon anion will then undergo another elimination reaction, where the bromine atom will leave, resulting in the formation of a triple bond.

The final product after this step will be:
```
CH3-CH2-C≡CH
```
This compound is 1-butyne.

### Conclusion
The major product of the overall reaction is 1-butyne (CH3-CH2-C≡CH).

### Final Answer
The major product of the reaction is **1-butyne** (CH3-CH2-C≡CH).

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