15. Which annulene would you not expect to be aromatic?
(A) [6]Annulene
(B) [14]Annulene
(C) [16]Annulene
(D) [18]Annulene
(E) [22]Annulene

16. Which the following combination best answer the following questions (step-i to step-iii)?(i) what type of reaction is step-(i)?(ii) which is the correct condition for step-(ii)?(iii) which is the correct final product for step-(iii)? (A)(SN2) (CF3C(O)OOH) (cyclopropane) (B)(E1) (H2O2,NaOH) (cyclopropane) (C) (E1cb) (CF3C(0)OOH) (cyclopropane) (D)(E1cb) (CF3C(O)OOH) (epoxide) (E) (E2) (H2O2,NaOH) (epoxide)

17. Remdesivir, one of the most popular molecules in the past three years, was approved or authorized for emergency use to treat COVID- 19 in numerous countries. How many stereogenic centers are there in Remdesivir? (A) 4 (B) 5 (C) 6 (D) 7 (E) 8

18. (continued) Consider the 1H-NMR spectrum of very pure Remdesivir. Presuming that Jab is sufficiently different from Jbc and that the instrument has sufficient resolving power. Assuming the maximum multiplicity of signals and non-superposition of peaks, what is the expected signal splitting pattern for each signal, in the order (Ha, Hb, Hc). Note: s: singlet, d: doublet, t: triplet, dd: doublet of doublet, dt: doublet of triplet (A) d, dd, dt (B) s, dd, dt (C) d, dd, d (D) d, t, d (E) s, t, dt

19, In the following reactions, which is the correct major product? (A)(B)(C) (D)(E)

20. Starting with benzene, the best method for preparing para-nitrobenzoic acid is: (A) HNO3/H2SO4； then CH3CI/AlCl3； then separation of isomers； then KMnO4/-OH/heat, followed by H3O+. (B) CH3CI/AICl3； then HNO3/H2SO4； then separation of isomers； then KMnO4/-OH/heat, followed by H30t. (C) CH3CI/AICl3； then KMn04/-OH/heat, followed by H3O+； then HNO3/H2SO4. (D) HNO3/H2SO4； then KMnO4/-OH/heat, followed by H3O+； then CH3CI/AICl3. (E) HNO3/H2SO4； then CO2, followed by H3O+.

21. Rank the aromaticities of the following compounds from most stable to least stable. (i) thiophene (ii) benzene (iii) pyrrole (iv) furan (A) ii＞i＞iii ＞iv (B) ii＞iv＞iii＞i (C) ii＞iv＞i＞iii (D) ii＞iii＞iv＞i (E) iv＞ii＞i＞iii

22. Which of the following is true about the Witting reaction? (A) The formation of carbon-carbon double bond from carbonyl compounds (aldehydes and ketones) and triphenylphosphite is known as the Witting reaction. (B) The Horner-Wadsworth-Emmons reaction is a variation of the Witting reaction. The major is usually the (Z)-alkene isomer. (C) The Horner-Wadsworth-Emmons reaction involves use of a phosphonate ester instead of a triphenylphosphonium salt. (D) A cis oxaphosphetane intermediate is formed to produce a ( E )-alkene in the Wittig reaction. (E) All of these choices.

23. List of the following acid derivatives from most reactive carbonyl to least reactive carbonyl toward Grignard reagent. (i) acid chloride (ii) carboxylic acid (iii) acid anhydride (iv) amide (v) ester. (A) ii＞v＞iv＞iii＞i (B)i＞iii＞v＞ii ＞iv (C) i＞iii＞v＞iv＞ii (D) iii＞i＞v＞iv＞ii (E) iii＞i＞v＞ii＞iv

24. Malonic ester (diethyl malonate) is treated successively with sodium ethoxide (1 eq.), ethyl bromide, potassium tert-butoxide, isobutyI chloride, hot aqueous NaOH, HCI, and heat. What is the final product? (A) 4-Ethyl-2-methylpentanoic acid (B) 6-Methylheptanoic acid (C) 2-Ethyl-3-methylpentanoic acid (D) 2-Ethyl-4-methylpentanoic acid (E) EthylisobutyImalonic acid

25. Arrange the compounds below in an order of increasing basicity.                                     (A) ii＜ii＜i＜v＜iv (B) i＜v＜ii＜iii＜iv (C) i

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