When semicarbazide reacts with a ketone(or aldehyde) to form semicarbazone. Only one nitrogen atom of semicarbazide acts as a nucleophile and attack the carbonyl carbon of the ketone. The product of the reaction consequently is $R_{2} C = N - N H - C O {N H}_{2}$ rather than $R_{2} C = N C O N H - {N H}_{2}$ . What factor account for the fact that two nitrogen atoms of semicarbazide are relatively non nucleophilic?

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Solution

There is no available lone pair on nitrogen atom in semicarbozone, i.e., why two nitrogen atoms of semicarbozide are relatively non- nucleophilic.

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Q. Give a plausible explanation for the following.
There are two

N H_{2}

groups in semicarbazide. However, only one such group is involved in the formation of semicarbazones.

Q. Assertion :There are two

{- N H}_{2}

groups in semicarbazide Reason: One group is involved in the formation of semicarbazones

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Q. Consider the following statements
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- N H_{2}

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(ii) Cyclohexane froms cyanohydrin in good yield but

2, 2, 6 - t r i m e t h y l c y c l o h e x a n o n e

does not.
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α - h y d r o g e n s

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