Question

Draw the structure of the semicarbazone of acetone.

Hint:

Semicarbazones are solid crystalline derivatives of aldehydes and ketones and are frequently used for identification purposes because of their sharp melting points.

Answer 1

Step 1: Reagents and reaction type.
Acetone ($CH_3COCH_3$) reacts with semicarbazide ($NH_2NHCONH_2$). The $-NH_2$ group acts as a nucleophile and attacks the electrophilic carbonyl carbon of acetone (nucleophilic addition).
Step 2: Elimination of water.
After addition, a molecule of water is eliminated and the $C{=}O$ bond is converted to a $C{=}N$ bond, producing the crystalline semicarbazone derivative.
Step 3: Product structure.
\[ CH_3COCH_3 + NH_2NHCONH_2 \rightarrow (CH_3)_2C{=}NNHCONH_2 + H_2O \] \[ \boxed{(CH_3)_2C{=}NNHCONH_2} \]