Concept:Semicarbazones are formed when a carbonyl compound like a ketone reacts with semicarbazide.
Explanation:Semicarbazide has the formula
NH2−NH−CONH2.
In this reaction, the ketone reacts with semicarbazide in acidic medium to give a semicarbazone.
The general reaction is:
R2C=O+NH2−NH−CONH2→R2C=N−NH−CONH2+H2ONow, check the given options:
Option A,
NH2OH, would give an oxime.
Option C,
NH2−NH−C6H5, would give a phenylhydrazone.
Option D,
NH2−NH2, would give a hydrazone.
Only option B matches semicarbazide, which produces a semicarbazone.
Therefore, reagent
R is semicarbazide.
Answer:Option B:
NH2−NH−CONH2