Consider the reaction
`RCHO + NH_(2)NH_(2) rarr R - CH = N NH_(2)`
What sort of reaction is it?

Options

A. Free radical addition – elimination reaction
B. Electrophilic substitution-elimination reaction
C. Nucleophilic addition – elimination reaction
D. Electrophilic addition – elimination reaction

Explanation

To determine the type of reaction represented by the equation:

\[ \text{RCHO} + \text{NH}_2\text{NH}_2 \rightarrow \text{RCH}=\text{NNH}_2 \]

we can analyze the components and the process involved in the reaction step by step.

### Step 1: Identify the Reactants
- **RCHO**: This is an aldehyde, where R is an alkyl or aryl group.
- **NH2NH2**: This is hydrazine, a nucleophilic reagent.

### Step 2: Understand the Reaction Mechanism
- In the reaction, the carbonyl carbon (C=O) of the aldehyde is electrophilic due to the partial positive charge on it (because oxygen is more electronegative).
- The nitrogen atoms in hydrazine (NH2NH2) have lone pairs of electrons, making them nucleophilic.

### Step 3: Nucleophilic Attack
- The nucleophile (hydrazine) attacks the electrophilic carbon of the aldehyde. This leads to the formation of a tetrahedral intermediate.

### Step 4: Formation of the Product
- After the nucleophilic addition, a water molecule is eliminated from the intermediate, resulting in the formation of the double bond between carbon and nitrogen, producing the final product \( \text{RCH}=\text{NNH}_2 \).

### Step 5: Classifying the Reaction
- Since the reaction involves a nucleophile attacking an electrophile (nucleophilic addition) and the elimination of a water molecule (elimination), we classify this reaction as a **nucleophilic addition-elimination reaction**.

### Final Answer
The reaction is classified as a **nucleophilic addition-elimination reaction**.

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