ORGANIC CHEMISTRY EXAM COMPLETE QUESTIONS WITH 100% VERIFIED ANSWERS 2026/2027

ORGANIC CHEMISTRY EXAM COMPLETE QUESTIONS WITH 100% VERIFIED ANSWERS 1. Which of the following best explains why the carbonyl carbon of an aldehyde is more electrophilic than that of a ketone? A) Aldehydes have greater steric hindrance at the carbonyl carbon. B) Ketones are more polarized due to two electron-donating alkyl groups. C) Aldehydes have only one electron-donating alkyl group, making the carbon less electron-rich and more reactive toward nucleophiles. D) Aldehydes undergo enolization faster, increasing electrophilicity. ________________________________________ 2. What is the major organic product formed when 2-pentanone is treated with excess NaOCl and NaOH under haloform reaction conditions? A) Pentanoic acid B) 2-Pentanol C) Sodium butanoate + CHI₃ (yellow precipitate) D) Sodium pentanoate + CHI₃ ________________________________________ 3. Which spectroscopic change is most consistent with conversion of benzaldehyde to benzyl alcohol? A) Loss of the carbonyl stretch (~1720 cm⁻¹) and appearance of a broad O–H stretch (~3300 cm⁻¹) B) Appearance of a C–H stretch at 2700 cm⁻¹ and a carbonyl stretch at 1680 cm⁻¹ C) Shift of the carbonyl stretch from 1720 cm⁻¹ to 1705 cm⁻¹ with no new O–H D) Loss of the aldehyde C–H stretch (~2720 cm⁻¹) and carbonyl stretch, gain of broad O–H ________________________________________ 4. A compound with molecular formula C₄H₈O shows a strong IR absorption at 1715 cm⁻¹ and a singlet in the ¹H NMR at δ 2.1 ppm (6H). No other signals. What is the structure? A) Butanal B) 2-Butanone C) 3-Buten-2-ol D) 2-Methylpropanal ________________________________________ 5. Which sequence would successfully convert acetophenone to benzoic acid without side products? A) Ozonolysis followed by H₂O₂ B) Haloform reaction (I₂/NaOH) followed by acidification C) KMnO₄ (cold, dilute) then LiAlH₄ D) PCC then Jones reagent ________________________________________ 6. In the Robinson annulation, the first step is typically: A) Michael addition of an enolate to an α,β-unsaturated ketone B) Aldol addition followed by dehydration C) Claisen condensation D) Diels–Alder cycloaddition ________________________________________ 7. What is the product when ethyl acetoacetate is treated with 1 equivalent of NaOEt followed by benzyl bromide, then heated with dilute HCl? A) 3-Benzyl-2-butanone B) 4-Phenyl-2-butanone C) 5-Phenyl-2-pentanone D) 2-Benzyl-3-butanone ________________________________________ 8. Which of the following enolates is most stable (least basic)? A) Enolate of acetone B) Enolate of ethyl acetoacetate C) Enolate of cyclohexanone D) Enolate of acetophenone ________________________________________ 9. The ¹H NMR of a compound shows δ 1.0 (t, 3H), 2.1 (s, 3H), and 2.5 (q, 2H). This corresponds to: A) 3-Pentanone B) 2-Pentanone C) Butanal D) Ethyl acetate ________________________________________ 10. Which reaction will yield an α,β-unsaturated ketone as the major product? A) Aldol condensation of cyclohexanone with itself B) Claisen condensation of ethyl acetate C) Reduction of benzophenone with NaBH₄ D) Haloform reaction of methyl ethyl ketone ________________________________________ 11. A ketone with formula C₆H₁₂O gives a positive iodoform test and forms a yellow precipitate with 2,4-DNP. Its ¹H NMR shows a singlet (3H) at δ 2.1, a septet (1H) at δ 2.6, and a doublet (6H) at δ 1.1. The structure is: A) 2-Methyl-3-pentanone B) 3-Methyl-2-butanone C) 2-Hexanone D) 4-Methyl-2-pentanone ________________________________________ 12. Which carbonyl compound is most reactive toward nucleophilic addition? A) Acetophenone B) Benzaldehyde C) Formaldehyde D) 2-Methylcyclohexanone ________________________________________ 13. In a Wolff–Kishner reduction, the carbonyl group of benzaldehyde is converted to: A) Toluene B) Benzyl alcohol C) Benzoic acid D) Benzene ________________________________________ 14. The product of a crossed Claisen condensation between methyl benzoate and methyl propanoate using NaOMe is (after acidic workup): A) Methyl 2-methyl-3-oxo-3-phenylpropanoate B) Methyl 3-oxo-2-methyl-3-phenylpropanoate C) Methyl 3-oxo-3-phenylpropanoate D) Methyl 2-benzoylpropanoate ________________________________________ 15. Which of the following cannot undergo an intramolecular aldol reaction under basic conditions? A) Heptane-2,6-dione B) Hexane-3,4-dione C) Octane-2,7-dione D) Nonane-2,8-dione ________________________________________ 16. A compound with IR peak at 1685 cm⁻¹ (strong), ¹H NMR: δ 7.3-7.9 (m, 5H), 2.6 (t, 2H), 2.2 (t, 2H), 2.1 (s, 3H). This is: A) 4-Phenyl-2-butanone B) 5-Phenyl-2-pentanone