【單選題】每題 2 分，共計 40 分，答錯一題倒扣 0.5 分，倒扣至本大題零分為止，未作答，不給分亦不扣分。

61. What is the product of the following reaction?

1. The Keq for the interconversion for the two chair forms of methylcyclohexane at 25 °C is 18. What % of the chair conformations feature an axial methyl group? (A) 95 (B) 75 (C) 50 (D) 25 (E) 5

2. What is the name of the major organic product of the following reaction?  (A) 3,3-dimethyl-1-butanol (B) 3,3-dimethyl-2-butanol (C) 2,3-dimethyl-2-butanol (D) 2,3-dimethyl-1-butanol (E) 4-methyl-2-petanol

3. How many diastereomer(s) exist for the compound below?  (A) 2 (B) 4 (C) 6 (D) 8 (E) 0

4. Which of the following statements is (are) true for the Diels-Alder reaction? (A) When the diene is electron-rich, the reaction works best when the dienophile contains one or more electron-withdrawing groups conjugated to its C=C. (B) Substituents which are cis in the dienophile remain cis in the product. (C) Dienes which cannot achieve an s-cis conformation do not react in Diels-Alder reactions. (D) Secondary orbital interactions typically cause the endo product to be favored kinetically over the exo. (E) All of the above.

5. What is the major product of the following reaction?

6. Which sequence of reagents works best to convert 3-hexene to 3-hexyne? (A) 1. HCl 2. NaNH2 (B) 1. BH3．THF 2. HO- , H2O2 3. NaNH2 (C) 1. NaNH2 2. HI 3. H3O+ (D) 1. Br2, CH2Cl2 2. NaNH2 (excess) (E) 1. Cl2, CH2Cl2 2. NaCN(excess)

7. Which of the following technique(s) can readily distinguish between: (A) NMR (B) IR (C) MS (D) A and B (E) A and C

8. What is the major product of the following reaction?

9. What is the major product of the following reaction?

10. What is the major product from the following rearrangement?

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