The synthesis of 3-octyne is achieved by adding a bromoalkane into a mixture of sodium amide and alkyne. The bromoalkane and alkyne, respectively, are

Options

A. (a) `BrCH_2CH_2CH_2CH_2CH_3` and `CH_3CH_2C-=CH`
B. (b) `BrCH_2CH_2CH_3` and `CH_3CH_2CH_2-=CH`
C. (c) `BrCH_2CH_2CH_2CH_2CH_3` and `CH_3C-=CH`
D. (d) `BrCH_2CH_2CH_2CH_3` and `CH_3CH_2C-=CH`

Explanation

To synthesize 3-octyne using a bromoalkane and an alkyne in the presence of sodium amide (NaNH2), we need to identify the appropriate bromoalkane and alkyne. Let's break down the solution step by step.

### Step 1: Understand the structure of 3-octyne
3-octyne has the molecular formula C8H14 and the structure:
- CH3-CH2-C≡C-CH2-CH2-CH3
This indicates that the alkyne is located at the third carbon of the chain.

### Step 2: Identify the alkyne
To create 3-octyne, we need to start with a suitable alkyne. The simplest alkyne that can be used is 1-butyne (C4H6), which has the structure:
- CH3-CH2-C≡C-H

### Step 3: Identify the bromoalkane
Next, we need a bromoalkane that will provide the necessary carbon chain to reach the octyne. The bromoalkane should have a structure that allows for the addition of a carbon chain to the alkyne. The appropriate bromoalkane is 1-bromopropane (C3H7Br), which has the structure:
- CH3-CH2-CH2-Br

### Step 4: Write the reaction
The reaction can be summarized as follows:
1. The sodium amide (NaNH2) deprotonates the alkyne (1-butyne) to form a nucleophilic anion.
2. This anion then attacks the bromoalkane (1-bromopropane) via an SN2 mechanism, leading to the formation of 3-octyne.

The overall reaction can be represented as:
\[ \text{CH}_3\text{CH}_2\text{C}\equiv\text{C}\text{H} + \text{CH}_3\text{CH}_2\text{CH}_2\text{Br} \xrightarrow{\text{NaNH}_2} \text{CH}_3\text{CH}_2\text{C}\equiv\text{C}\text{CH}_2\text{CH}_2\text{CH}_3 \]

### Step 5: Conclusion
Thus, the bromoalkane and alkyne needed to synthesize 3-octyne are:
- Bromoalkane: 1-bromopropane (CH3-CH2-CH2-Br)
- Alkyne: 1-butyne (CH3-CH2-C≡C-H)