23. Which of the following is an organometallic compound?
(A)
(B) NaCl
(C) PH₃
(D)Ti(NMe₂)₄
(E) Pd(OAc)₂

19.Which of the following description about SN2 reaction is incorrect? (A) The rate of the reaction is second order. (B) Inversion of configuration at the reacting center will occur. (C) There is no intermediate in an SN2 reaction. (D) Alkyl fluoride is very reactive in SN2 reaction. (E) In Sx2 reaction, using polar aprotic solvents will give a faster reaction rate compare to polar protic solvents.

20. Which of the following statements is correct? (A) A chiral compound will always react to give a chiral product. (B) The most stable conformation of tert-butylcyclohexane is with the tert-butyI group at the axial position. (C) Aryl amines can be synthesized by reduction of nitroarenes. (D) The Diels-Alder reaction involves rearrangement of electrons between the two HOMOs of the two reactants. (E) A hard nucleophile will prefer to react with an α.β-unsaturated carbonyl compound in 1,4- addition instead of 1,2-addition.

21. Which of the following has the smallest radius? (A)(B)(C)(D)(E) all of the above

22. Which of the following is not an inorganic compound? (A)BeH2(B)BH3 (C)CH4 (D)NH3(E) H2O

24. Which of the following has the largest electronegativity? (A) B (B) C (C)N (D) O (E) F

25. The E/Ru value for an electron at n = 1 in a He+ cation, where E = energy, = Rydberg constant =13.61 eV, n = principal quantum number, is (A)-1 (B)-2 (C)-3 (D)-4 (E) none of the above

26. Among the following compounds, which is not isoelectronic with the others? (A) BH3 (B) CH4 (C) NH3 (D) H2O (E) HF

複選題27. Among the following compounds, whose molecular dipole is not zero? (A)PF5(B)PF3Cl2(C) PF2Cl3 (D)P4 (E) BF3

28. Among the following compounds, which has the largest bond angle? (A) NF3 (B) PF3 (C) AsF3 (D) SbF3 (E) all of the above

29. Among the following compounds, whose point group is ? (A) BF3 (B) CF4 (C) NF3(D) SF4 (E) none of the above