Which of the following reactions does not give `RCONH_(2)`?

Options

A. `R-C-=N+H_(2)Ooverset(HCl)(to)`
B. `RCONH_(4)overset("heat")(to)`
C. `RCNoverset(H_(2)//Ni)(to)`
D. `(RCO)_(2)O+overset(NH_(3))(to)`

Answer

To determine which of the following reactions does not give `RCONH2`, we need to analyze the reactions provided.

### Step-by-Step Solution:

1. **Understanding the Reactions**:
- The question asks about reactions that yield `RCONH2`, which is an amide.
- We need to consider common reactions that produce amides from their precursors.

2. **Thermal Decomposition of Ammonium Salts**:
- When ammonium salts are heated, they undergo thermal decomposition to form amides and water.
- The general reaction can be represented as:
\[ RCOONH4 \xrightarrow{\text{heat}} RCONH2 + H2O \]
- This reaction does produce `RCONH2`.

3. **Reaction of Acyl Chlorides with Ammonia**:
- Acyl chlorides react with ammonia to form primary amides.
- The reaction can be represented as:
\[ RCOCl + NH3 \rightarrow RCONH2 + HCl \]
- This reaction also produces `RCONH2`.

4. **Reaction of Acyl Chlorides with Amines**:
- Acyl chlorides can also react with primary and secondary amines to form secondary and tertiary amides, respectively.
- For example:
\[ RCOCl + R'NH2 \rightarrow RCONHR' + HCl \]
- This reaction produces amides as well.

5. **Identifying the Reaction that Does Not Produce `RCONH2`**:
- The question implies that one of the reactions does not yield `RCONH2`.
- The reaction of ammonium salts when heated produces `RCONH2`, while the reaction of acyl chlorides with ammonia or amines does produce amides.
- However, if we consider the reaction of ammonium salts with heat, it produces `RCONH4` (the ammonium salt of the amide) initially, which does not yield `RCONH2` directly upon heating without further steps.

6. **Conclusion**:
- Therefore, the reaction that does not give `RCONH2` is the thermal decomposition of ammonium salts when they are not fully decomposed to yield the amide directly.

### Final Answer:
The correct option is **B**, as it represents the reaction that does not yield `RCONH2`.