Question 23 of 26intermediate🔧 ApplyShort Answer5 marks

Complete each synthesis by giving missing starting material, reagent or products

(i)

Ethylbenzene → KMnO₄ → KOH, heat

Answer

Benzoic acid (C₆H₅COOH)

(ii)

Benzoic acid → SOCl₂ → heat

Answer

Benzoyl chloride (C₆H₅COCl)

(iii)

C₆H₅CHO → H₂NCONHNH₂

Answer

Benzaldehyde semicarbazone (C₆H₅CH=NNHCONH₂)

(iv)

C₆H₅CHO → [Ag(NH₃)₂]⁺ → Benzaldehyde

Answer

Benzoic acid (C₆H₅COOH)

(v)

C₆H₅CHO + CH₃CH₂CHO → dil.NaOH → Δ

Answer

Cinnamaldehyde (C₆H₅CH=CHCHO)

(vi)

CH₃COCH₂COOC₂H₅ → (i) NaBH₄ (ii) H⁺

Answer

Ethyl 3-hydroxybutanoate (CH₃CH(OH)CH₂COOC₂H₅)

(vii)

CH₃CH₂CH₂COOC₂H₅ → (i) NaBH₄ (ii) H⁺

Answer

Butan-1-ol (CH₃CH₂CH₂CH₂OH)

(viii)

Cyclohexanol → CrO₃

Answer

Cyclohexanone

(ix)

Cyclohexene → (i) O₃ (ii) Zn-H₂O

Answer

Hexanedial (Adipaldehyde)

Explanation

Each reaction involves standard organic transformations: (i) KMnO₄/KOH oxidizes alkyl side chains on benzene to carboxylic acids; (ii) SOCl₂ converts carboxylic acids to acid chlorides; (iii) Semicarbazide forms semicarbazones with aldehydes; (iv) Tollens' reagent oxidizes aldehydes to carboxylates; (v) Cross-aldol condensation between benzaldehyde and propanal; (vi-vii) NaBH₄ reduces carbonyl groups; (viii) CrO₃ oxidizes secondary alcohols to ketones; (ix) Ozonolysis cleaves alkenes to carbonyl compounds.

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