Which set of reagents are needed to synthesize the given unsymmetrical alkyne `CH_3-C-=C-CH_2-CH_3` ?

Options

A. Acetaldyde , 1 - bromopropane and conc.`H_2SO_4`
B. Ethyne , iodomethane , iodothane and sodamide
C. 1,2 - dichloroethane , 1 - propanol and alcoholic potassium hydroxide
D. Ethene , iodoethane , iodomethane and potassium hydroxide

Answer

To synthesize the unsymmetrical alkyne \( CH_3-C \equiv C-CH_2-CH_3 \), we can follow these steps:

### Step 1: Start with the terminal alkyne
We can begin with a terminal alkyne, such as propyne (\( CH_3-C \equiv CH \)).

### Step 2: Deprotonation
React the terminal alkyne with sodium amide (\( NaNH_2 \)). This will deprotonate the terminal alkyne to form an acetylide ion:
\[ CH_3-C \equiv CH + NaNH_2 \rightarrow CH_3-C \equiv C^{-}Na^{+} \]

### Step 3: Alkylation with iodomethane
Next, we can perform an alkylation reaction using iodomethane (\( CH_3I \)). The acetylide ion will act as a nucleophile and attack the iodomethane, resulting in the formation of a new alkyne:
\[ CH_3-C \equiv C^{-}Na^{+} + CH_3I \rightarrow CH_3-C \equiv C-CH_3 + NaI \]

### Step 4: Deprotonation again
Now we will again use sodium amide (\( NaNH_2 \)) to deprotonate the newly formed alkyne:
\[ CH_3-C \equiv C-CH_3 + NaNH_2 \rightarrow CH_3-C \equiv C^{-}Na^{+}-CH_3 \]

### Step 5: Alkylation with iodoethane
Finally, we will perform a second alkylation using iodoethane (\( C_2H_5I \)):
\[ CH_3-C \equiv C^{-}Na^{+}-CH_3 + C_2H_5I \rightarrow CH_3-C \equiv C-CH_2-CH_3 + NaI \]

### Final Product
The final product is the unsymmetrical alkyne \( CH_3-C \equiv C-CH_2-CH_3 \).

### Summary of Reagents
The reagents used in this synthesis are:
1. Sodium amide (\( NaNH_2 \))
2. Iodomethane (\( CH_3I \))
3. Iodoethane (\( C_2H_5I \))

### Answer
The correct set of reagents needed to synthesize the given unsymmetrical alkyne is option B: Sodium amide, iodomethane, and iodoethane.

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