`CH_(3)CH_(2)COOH underset("red P")overset(Br_(2))to A overset(Br_(2))toB`
What is B?

Options

A. `CH_(3)CH_(2)Br`
B. `CH_(3)CH_(2)CHO`
C. `CH_(3)-underset(Br)underset(|)(C)H-COOH`
D. `Br-CH_(2)-CH_(2)-COOH`

Answer

To solve the problem step by step, we will analyze the reactions involved with the given compound, propanoic acid (CH₃CH₂COOH), and the reagents red phosphorus (red P) and bromine (Br₂).

### Step 1: Understand the Initial Compound
The initial compound is propanoic acid, which has the molecular formula CH₃CH₂COOH. It is a carboxylic acid with a three-carbon chain.

**Hint:** Identify the structure of propanoic acid to understand its functional groups.

### Step 2: Reaction with Red Phosphorus and Bromine
When propanoic acid reacts with red phosphorus and bromine, it forms an intermediate compound. The red phosphorus reacts with bromine to form phosphorus tribromide (PBr₃).

The reaction can be represented as:
\[ \text{CH}_3\text{CH}_2\text{COOH} + \text{PBr}_3 \rightarrow \text{CH}_3\text{CH}_2\text{COBr} + \text{HBr} + \text{P(OH)}_3 \]

Here, propanoic acid is converted to bromo-propanoic acid (CH₃CH₂COBr).

**Hint:** Remember that the carboxylic acid group (–COOH) is converted to a bromo group (–Br) in this step.

### Step 3: Identify Product A
The product A from the above reaction is bromo-propanoic acid (CH₃CH₂COBr).

**Hint:** Write down the structure of bromo-propanoic acid to visualize the product.

### Step 4: Further Reaction with Bromine
Next, the product A (CH₃CH₂COBr) undergoes another reaction with bromine (Br₂). This reaction typically leads to the formation of a dibromo compound through an electrophilic substitution reaction.

The reaction can be represented as:
\[ \text{CH}_3\text{CH}_2\text{COBr} + \text{Br}_2 \rightarrow \text{CH}_3\text{CH}_2\text{CBr}_2\text{H} \]

This results in the formation of 2,2-dibromopropanoic acid.

**Hint:** Consider how the bromine adds to the carbon adjacent to the carbonyl group in the bromo-propanoic acid.

### Step 5: Identify Product B
The final product B is 2,2-dibromopropanoic acid, which can be represented as CH₃C(Br)(Br)COOH.

**Hint:** Make sure to write down the complete structure of 2,2-dibromopropanoic acid to confirm the product.

### Conclusion
Thus, the final answer for product B is **2,2-dibromopropanoic acid**.

### Summary of Steps:
1. Identify the initial compound (propanoic acid).
2. React with red phosphorus and bromine to form bromo-propanoic acid (A).
3. React bromo-propanoic acid with bromine to form 2,2-dibromopropanoic acid (B).

### Final Answer:
**B = 2,2-dibromopropanoic acid (CH₃C(Br)(Br)COOH)**