A hydrocarbon (A) reacts with sodium amide and then with ethylbromide to produce another hydrocarbon (B) which on ozonolysis by oxidative method yields propanoic acid only. The hydrocarbons (A) and (B) are, respectively.

Options

A. but-1-yne and hex-3-yne
B. but-1-yne and hex-3-ene
C. propyne and hex-3-yne
D. propyne and pent-2-yne

Explanation

To solve the problem, we need to identify the hydrocarbons (A) and (B) based on the reactions described. Let's break down the steps systematically.

### Step 1: Identify Hydrocarbon B
The problem states that hydrocarbon (B) undergoes ozonolysis and produces propanoic acid. Ozonolysis typically cleaves double or triple bonds in alkenes or alkynes to form carbonyl compounds (aldehydes or ketones), which can further oxidize to carboxylic acids.

Since the only product from the ozonolysis is propanoic acid (C2H5COOH), we can deduce that hydrocarbon (B) must have a structure that, when cleaved, yields propanoic acid.

### Step 2: Determine the Structure of Hydrocarbon B
To yield propanoic acid, hydrocarbon (B) must contain a carbon-carbon triple bond (alkyne) that, when cleaved, results in the formation of propanoic acid.

The simplest structure that fits this description is 1-butyne (C4H6), which can be represented as:
- **B: 1-butyne (C4H6)**

When ozonolysis occurs on 1-butyne, it can yield two moles of propanoic acid.

### Step 3: Identify Hydrocarbon A
Now, we need to determine hydrocarbon (A). The problem states that hydrocarbon (A) reacts with sodium amide (NaNH2) and then with ethyl bromide (C2H5Br) to form hydrocarbon (B).

Sodium amide is a strong base and will deprotonate terminal alkynes to form a nucleophilic alkyne anion. This anion can then undergo an SN2 reaction with ethyl bromide.

To produce 1-butyne (B), hydrocarbon (A) must be a terminal alkyne. The simplest terminal alkyne that can produce 1-butyne through this reaction is ethyne (acetylene, C2H2).

### Step 4: Write the Final Answer
Thus, we conclude:
- **Hydrocarbon A: Ethyne (C2H2)**
- **Hydrocarbon B: 1-butyne (C4H6)**

### Summary
- Hydrocarbon A is Ethyne (C2H2).
- Hydrocarbon B is 1-butyne (C4H6).