5. Which of the following Newman projections does not represent 2-methylhexane?   
(A) 1
(B) 2
(C) 3
(D) 4
(E) both 2 and 3

I. Choose one correct answer for the following questions 【單選題】每題 1 分，共計 60 分，答錯 1 題倒扣 0.25 分，倒扣至本大題零分為止，未作答，不給分亦不扣分。1. According to atomic theory: (A) The nucleus is positively charged (B) The nucleus contains both charged and uncharged particles (C) The electrons contribute very little to the total mass of the atom (D) The electrons are located in the atomic space outside the nucleus (E) All of the above.

2. A coenzyme frequently encountered in transamination reactions is (A) Tetrahydrofolate (B) Pyridoxal phosphate (C) Thiamine pyrophosphate (D) Biotin (E) NADH

3. Which one of the following structures represents a different compound from the other three? (A) 1 (B) 2 (C) 3 (D) 4 (E) All of the above are the same.

4. Which of the standard amino acids is achiral?(A) Lysine (B) Proline (C) Valine (D) Alanine (E) Glycine

6. 2,3-Dibromobutane can exist three stereoisomers as shown below. What stereoisomers would be formed by the following reaction?  (A) 1 only (B) 2 only (C) 3 only (D) 1 and 2 (E) 2 and 3

7. In the following structures, the protons pointed by arrow (on C2) which belong to diastereotopic hydrogens. (A)(B)(C) (D) (E) None of the above.

8. What is the correct IUPAC systematic name for the following compound? (A) 1,2-Dichlorocyclohexene (B) 2,3-Dichlorocyclohexene (C) 1,6-Dichlorocyclohexene (D) 1,2-Dichloro-2-cyclohexene (E) None of the above.

9. What is the formal charge on the nitrogen atom indicated with the arrow in the following compound?(A) 0 (B) −1 (C) +1 (D) −2 (E) +2

10. Which of the following nucleophiles reacts with MeI in greatest rate in an aqueous solution? (A) Me (B) MeOH (C) HO (D) CH3CO2 (E) MeS

11. Which of the following compounds would have a greater dipole moment than you expect? (A)(B)(C)(D)(E) None of the above.