20. When pent-1-ene is treated with mercury(II) acetate in methanol and the resulting product is reacted with NaBH₄, what is the primary organic compound which results?
(A) 3-ethoxypentane
(B) 1-methoxypentane
(C) 1-ethoxypentane
(D) 2-ethoxypentane
(E) 2-methoxypentane

16. Consider the data illustrated below. The formula of unknown compound is C9H9N IR (cm-1): 3050, 2950, 2240, 1630 1H NMR (δ): 7.5 (2H, d), 7.1 (2H, d), 2.3 (2H, q), 0.9 (3H, t) 13C NMR (δ): 137 (s), 130, (s), 126 (d), 122 (d), 95 (s), 25 (t), 15 (q) The structure of unknown compound is? (A)(B)(C)(D)(E)

17. In electrophilic aromatic substitution reactions, the hydroxyl group is an o,p-director because: (A) it donates electron density to the ring by induction and destabilizes the meta sigma complex. (B) it donates electron density to the ring by induction and stabilizes the ortho and para sigma complexes. (C) it donates electron density to the ring by resonance and destabilizes the meta sigma complex. (D) it donates electron density to the ring by resonance and stabilizes the ortho and para sigma complexes. (E) None of the above.

18. (S)-2-Methylbutanal __________ upon sitting in an acidic or a basic aqueous solution. (A) racemizes (B) esterifies (C) inverts completely to the R configuration (D) hydrolyzes (E) irreversibly forms the hydrate

19. When a carbonyl is part of a conjugated π-network, the C=O stretch: (A) has a higher frequency than in a nonconjugated system. (B) has a lower frequency than in a nonconjugated system. (C) always occurs at 1710 cm-1 . (D) occurs around 2700 cm-1 . (E) cannot be distinguished from the C=O stretch in a nonconjugated system.

21. What is the major product of the following reaction?  (A) I (B) II (C) III (D) IV (E) None of the above.

22. Which of the following terms describes the mechanism of a Claisen rearrangement reaction? (A) Electrophilic addition (B) Nucleophilic addition (C) syn Elimination (D) Radical substitution (E) Pericyclic reaction

23. What is the major organic product obtained from the following reaction? (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

24. What is the major organic product obtained from the following sequence of reactions?  (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

25. What is the major product of the following reaction?  (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

26. Which of the following terms best describes the compound shown below? (A) a lecithin (B) a diterpene (C) a steroid (D) a glyceride (E) a prostaglandin