`R-NH-COH underset("pyridine")overset(POCl_(3))(to)` product. In the given reaction what will be the product.

Options

A. `R-N=C=O`
B. `N-overset(+)(N)-=C^(-)`
C. `R-C-=N`
D. None of these

Answer

To solve the question regarding the reaction of R-NH-COH with POCl3 in the presence of pyridine, we will follow these steps:

### Step 1: Identify the Reactants
We have the reactant R-NH-COH (which is an amide) and we are reacting it with POCl3 (phosphoryl chloride) in the presence of pyridine.

**Hint:** Identify the functional groups present in the reactant and the role of the reagents.

### Step 2: Understand the Role of POCl3
POCl3 is a dehydrating agent. It can facilitate the conversion of amides to isocyanates by removing water (dehydration).

**Hint:** Recall how dehydrating agents typically function in organic reactions.

### Step 3: Mechanism of Reaction
1. The nitrogen atom in the amide (R-NH-COH) has a lone pair that can attack the phosphorus atom in POCl3. This forms a positively charged intermediate.
2. The chlorine atom in POCl3 acts as a good leaving group and will leave, resulting in a positively charged nitrogen and a double bond between carbon and oxygen.

**Hint:** Consider the electron movement and the formation of intermediates during the reaction.

### Step 4: Formation of Isocyanate
After the formation of the intermediate, a proton (H+) is removed, leading to the formation of an isocyanate (R-N=C=O) as the final product. The nitrogen will carry a positive charge, and the carbon will be triple-bonded to nitrogen.

**Hint:** Think about the stability of the resulting product and the nature of the bonds formed.

### Step 5: Identify the Product
The product formed from this reaction is R-N=C=O, which is isocyanate.

**Hint:** Compare the final product with the options provided in the question to confirm the correct answer.

### Conclusion
The product of the reaction of R-NH-COH with POCl3 in the presence of pyridine is an isocyanate (R-N=C=O).

### Final Answer
The correct product is R-N=C=O (isocyanate).

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