Among the following which one does not act as an intermediate in hofmann rearrangement

Options

A. `RNCO`
B. `RCO overset(..)N`
C. `RCO overset(..)NHBr`
D. `RNC`

Explanation

To solve the question regarding which compound does not act as an intermediate in the Hofmann rearrangement, we will follow these steps:

### Step 1: Understand the Hofmann Rearrangement
The Hofmann rearrangement is a chemical reaction where an amide is converted into a primary amine with the loss of one carbon atom. This reaction typically involves the treatment of an amide with bromine (Br2) in the presence of a strong base, such as potassium hydroxide (KOH).

### Step 2: Identify the Reaction Mechanism
The mechanism of the Hofmann rearrangement involves several key intermediates:
1. Formation of N-haloamide (R-C(O)-N-H-Br).
2. Rearrangement to isocyanate (R-N=C=O).
3. Hydrolysis of isocyanate to form the final product, which is a primary amine (R-NH2).

### Step 3: Analyze the Given Options
Now, let's analyze the options provided in the question to determine which one does not act as an intermediate:
1. **R-N-C-O**: This represents an isocyanate, which is indeed an intermediate in the reaction.
2. **RCON**: This is an amide, which is the starting material and not an intermediate.
3. **RCONHBr**: This is the N-haloamide formed during the reaction, thus it is an intermediate.
4. **RNC**: This represents an alkyl isocyanide, which is not formed during the Hofmann rearrangement.

### Step 4: Conclusion
From the analysis, we can conclude that the compound that does not act as an intermediate in the Hofmann rearrangement is **RNC** (option 4).

Thus, the answer is:
**Option 4: RNC does not act as an intermediate in Hofmann rearrangement.**

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