Q.Draw and complete the following reaction scheme which starts with acetaldehyde. In each empty box, write the structural formula of the organic compound that would be formed.

The cyanide ion is a nucleophile that adds directly across acetone's polarised carbonyl double bond (no group is displaced), giving the addition product cyanohydrin — a textbook nucleophilic addition, typical of the carbonyl group's reactivity.

Acetone's carbonyl carbon is electrophilic (partial positive charge, due to oxygen's higher electronegativity polarising the $C=O$ bond). The cyanide ion, $CN^-$ (generated from HCN with a trace of base/KCN), is a good nucleophile that attacks this electrophilic carbon; the pi electrons of the $C=O$ bond shift onto oxygen, and after protonation of the resulting alkoxide, the tetrahedral addition product — 2-hydroxy-2-methylpropanenitrile (acetone cyanohydrin) — is formed: $CH_3COCH_3 + HCN \rightarrow (CH_3)_2C(OH)CN$ This is a nucleophilic addition (not substitution, since no leav …

Acetone condenses with 2,4-DNP to give acetone 2,4-dinitrophenylhydrazone, a classic carbonyl-identification derivative.

The carbonyl group of acetone reacts with the primary amino group of 2,4-dinitrophenylhydrazine (2,4-DNP) via nucleophilic addition–elimination (condensation), losing a molecule of water, to form a hydrazone:

$CH_3COCH_3 + H_2N-NH-C_6H_3(NO_2)_2 \rightarrow (CH_3)_2C=N-NH-C_6H_3(NO_2)_2 + H_2O$ …

Ketones react with hydroxylamine to form oximes, a classic carbonyl-to-C=N condensation.

Identifying the reaction: Conversion of the carbonyl group C=O of acetone into C=N-OH is oxime formation, a nucleophilic addition-elimination reaction typical of aldehydes/ketones with primary-amine-like nucleophiles.

Reagent: Hydroxylamine, $NH_2OH$ (commonly used as its hydrochloride salt, $NH_2OH\cdot HCl$, buffered with a mild base such as sodium acetate to free the nucleophilic amine).

Equation: …

Formaldehyde condenses with excess ammonia in a well-known reaction to form hexamethylenetetramine (urotropine).

Reasoning: Six molecules of formaldehyde react with four molecules of ammonia in a cyclic condensation to give hexamethylenetetramine (also called hexamine or urotropine), a cage-like heterocyclic compound used as a urinary antiseptic and as a precursor in the manufacture of certain resins/explosives (RDX):

$6HCHO + 4NH_3 \longrightarrow (CH_2)_6N_4\;(\text{hexamethylenetetramine}) + 6H_2O$ …

The carbonyl carbon of acetone is electrophilic, so the nucleophilic $CN^-$ (from HCN) adds to it, and after protonation of the resulting alkoxide the $C=O$ double bond becomes a single bond bearing both $-OH$ and $-CN$ — an addition, driven by a nucleophile, not a substitution.

Acetone, $(CH_3)_2C=O$, has a polarised carbonyl carbon ($\delta^+$) due to the electronegative oxygen. The cyanide ion $CN^-$ acts as a nucleophile, attacking this carbon and adding across the double bond; protonation of the resulting alkoxide by HCN/$H^+$ gives the cyanohydrin, $(CH_3)_2C(OH)CN$. Because a nucleophile adds to (rather than substitutes at) an unsaturated carbon, with no leaving group d …