Which of the following reagents can be used to prepare 2-butyne by simple organic transformations?

Options

A.
B. `CH_3-undersetunderset(Cl)|oversetoverset(Cl)|C-undersetunderset(Cl)|oversetoverset(Cl)|C-CH_3`
C. `CH_3CH_2-undersetunderset(Br)|oversetoverset(Br)|C-CH_3`
D. `CH_3-C Cl_3`

Answer

To prepare 2-butyne through simple organic transformations, we can consider the following steps based on the information provided in the video transcript.

### Step-by-Step Solution:

1. **Identify the Structure of 2-Butyne**:
- 2-Butyne is an alkyne with the molecular formula C4H6. Its structure can be represented as CH3-C≡C-CH3, indicating a triple bond between the second and third carbon atoms.

2. **Consider the Starting Materials**:
- To synthesize 2-butyne, we can start with a compound that has halogen atoms on adjacent carbon atoms. A common precursor for this transformation is 1,2-dichlorobutane (C4H8Cl2).

3. **Dehalogenation Reaction**:
- The first method involves a dehalogenation reaction. When 1,2-dichlorobutane is treated with zinc (Zn), the two chlorine atoms can be removed. The reaction can be represented as:
\[ \text{C4H8Cl2} + \text{Zn} \rightarrow \text{C4H6} + \text{ZnCl2} \]
- This results in the formation of a double bond, which can be further converted to a triple bond.

4. **Formation of 2-Butyne**:
- The removal of two moles of HCl (from the halogenated compound) leads to the formation of a triple bond, yielding 2-butyne.

5. **Alternative Method - Dehydrohalogenation**:
- Another method is to use a compound like 2-bromobutane (C4H9Br) and perform a dehydrohalogenation reaction. This can be done using alcoholic KOH (potassium hydroxide) to remove HBr:
\[ \text{C4H9Br} + \text{KOH (alc)} \rightarrow \text{C4H6} + \text{HBr} + \text{KBr} + \text{H2O} \]
- This reaction also leads to the formation of 2-butyne.

6. **Conclusion**:
- Therefore, both the dehalogenation of 1,2-dichlorobutane and the dehydrohalogenation of 2-bromobutane can be used to prepare 2-butyne.

### Final Answer:
The reagents that can be used to prepare 2-butyne by simple organic transformations are:
- 1,2-dichlorobutane with zinc (for dehalogenation).
- 2-bromobutane with alcoholic KOH (for dehydrohalogenation).