Question

Consider the reaction: ${ RCHO + NH2NH2 -> RCH = N - NH2 }$ What sort of reaction is it ?

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

Answer 1

The Correct Option is C

To determine the type of reaction represented by RCHO + NH_2NH_2 \rightarrow RCH = N - NH_2, let us analyze the reaction mechanism step-by-step:

1. The reaction involves an aldehyde, RCHO, reacting with hydrazine, NH_2NH_2.
2. The initial step involves the nucleophilic addition of the nitrogen atom from the hydrazine to the electrophilic carbon atom of the carbonyl group in the aldehyde.
3. This results in the formation of an unstable intermediate where the double bond in the carbonyl group is broken, and the carbon is bonded to the nitrogen from hydrazine.
4. Following the nucleophilic attack, there is an elimination of a water molecule (H₂O) to form the final product with a double bond between carbon and nitrogen, yielding RCH = N - NH_2.

The overall process, therefore, involves two main steps: a nucleophilic addition followed by elimination.

Now, let's justify why the correct answer is a Nucleophilic addition - elimination reaction:

• Free radical addition - elimination reaction: This type of reaction involves free radicals, which are not part of this mechanism.
• Electrophilic substitution-elimination reaction: This generally involves an electrophile attacking an electron-rich site, not applicable here.
• Electrophilic addition - elimination reaction: This involves an electrophile, but the initial step here is nucleophilic addition.

Therefore, the mechanism fits perfectly with the Nucleophilic addition - elimination reaction.