In osazone formation of three molecules of phenylhydrazine which is the correct statement.

Options

A. All the three molecules react in similar manner
B. Two molecules reacts in similar manner whereas the third reacts in different way
C. All the three molecules react in different way
D. Only two react in same manner but the third molecules remains unreacted

Explanation

To solve the question regarding the osazone formation with three molecules of phenylhydrazine, we can follow these steps:

### Step 1: Identify the Reactants
We start with a carbohydrate that has multiple hydroxyl groups. The structure can be represented as:
- CHO (aldehyde group)
- CHOH (alcohol groups)
- CH2OH (another alcohol group)

The reactant is a sugar molecule, and we are reacting it with phenylhydrazine (PhNH-NH2).

### Step 2: First Reaction with Phenylhydrazine
When the first molecule of phenylhydrazine reacts with the carbonyl carbon (aldehyde), a condensation reaction occurs. This results in the formation of a hydrazone and the release of a water molecule. The structure after the first reaction can be represented as:
- CH=N-NH-Ph (hydrazone formation)
- The rest of the sugar structure remains intact.

### Step 3: Second Reaction with Phenylhydrazine
In the second reaction, the compound formed from the first reaction has a secondary alcohol (OH group) that gets oxidized to a ketone. The reaction with phenylhydrazine again leads to the formation of another hydrazone. The structure after the second reaction can be represented as:
- CH=N-NH-Ph (from the first reaction)
- The secondary alcohol is oxidized to a ketone.

### Step 4: Third Reaction with Phenylhydrazine
The third molecule of phenylhydrazine reacts with the ketone formed in the second reaction. This also leads to a condensation reaction, resulting in the formation of another hydrazone and the release of a water molecule. The final structure can be represented as:
- CH=N-NH-Ph (from the second reaction)
- The ketone group reacts similarly to the aldehyde in the first reaction.

### Step 5: Analyze the Statements
Now, we can analyze the statements given in the question:
1. **All three molecules react in a similar manner.** - This statement is incorrect because the second reaction involves oxidation of the secondary alcohol to a ketone, which is different from the condensation reactions of the first and third.
2. **Two molecules react in a similar manner whereas the third reacts in a different manner.** - This statement is correct because the first and third reactions are condensation reactions, while the second involves oxidation.
3. **All three molecules react in a different way.** - This statement is incorrect as the first and third reactions are similar.
4. **The third molecule remains unreacted.** - This statement is incorrect because the third molecule does react.

### Conclusion
The correct statement is that **two molecules react in a similar manner whereas the third reacts in a different manner.** Therefore, the answer is option 2.

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