In the given reaction `CH_(3)-COOH underset(underset("(iii) "H_(2)O //H^(o+))("(ii) "NaCN))overset("(i) Red "-P+Br_(2))rarr(X)`
'X' will be

Options

A.
B. `COOH-CH_(2)-CH_(2)-COOH`
C.
D.

Answer

To determine the product 'X' from the given reaction sequence involving acetic acid (CH₃COOH), we will break down the reaction into three steps as described in the video transcript.

### Step 1: Reaction with Red Phosphorus and Bromine
1. **Starting Material**: Acetic acid (CH₃COOH).
2. **Reagents**: Red phosphorus (P) and bromine (Br₂).
3. **Reaction Type**: This is known as the Hell-Volhard-Zelinsky (HVZ) reaction, where the acidic hydrogen at the alpha position (the carbon adjacent to the carboxylic acid group) is replaced by bromine.
4. **Mechanism**: The red phosphorus and bromine will remove the hydrogen atom from the alpha carbon (CH₃-), resulting in the formation of a brominated acetic acid.
5. **Product**: The product after this step will be 2-bromoacetic acid (CH₂BrCOOH).

### Step 2: Reaction with Sodium Cyanide (NaCN)
1. **Starting Material**: 2-bromoacetic acid (CH₂BrCOOH).
2. **Reagent**: Sodium cyanide (NaCN).
3. **Mechanism**: The cyanide ion (CN⁻) acts as a nucleophile and attacks the carbon atom bonded to the bromine (the alpha carbon). The bromine atom leaves, resulting in the formation of a new compound.
4. **Product**: The product after this step will be 2-cyanoacetic acid (CH₂(CN)COOH).

### Step 3: Hydrolysis of the Cyanide Group
1. **Starting Material**: 2-cyanoacetic acid (CH₂(CN)COOH).
2. **Process**: Hydrolysis of the cyano group (CN) occurs in the presence of water (H₂O) and typically involves an acid or base to facilitate the reaction.
3. **Mechanism**: The cyano group is converted into a carboxylic acid group (-COOH) through hydrolysis.
4. **Product**: The final product after hydrolysis will be 2-hydroxyacetic acid (CH₂COOH), which is also known as lactic acid.

### Final Product
The final product 'X' after all three steps is 2-hydroxyacetic acid (CH₂COOH).

### Summary of Steps:
1. **Step 1**: CH₃COOH + P + Br₂ → CH₂BrCOOH (2-bromoacetic acid)
2. **Step 2**: CH₂BrCOOH + NaCN → CH₂(CN)COOH (2-cyanoacetic acid)
3. **Step 3**: CH₂(CN)COOH + H₂O → CH₂COOH (2-hydroxyacetic acid)