12. Which of the following species is the least nucleophilic?
(A) H₂0
(B) BF₃
(C) (CH₃)₃N
(D) CH₃O^-
(E) CH^- 

8. Consider the spectrum illustrated below. Which of the following structures will be best for this spectrum? (A)(B)(C)(D)(E) None of the above

9. The average mass of a boron atom is 10.81. If you were able to isolate a single boron atom, what is the chance that you would randomly get an atom with mass 10.81?  (A) 0% (B) 0.81% (C) about 11% (D) 10.81% (E) greater than 50%.

10. Which of the statements below correctly describes the chair conformations of trans-1,4-dimethylcyclohexane? | (A) The two chair conformations are of equal energy. | (B) The higher energy chair conformation contains one axial methyl group and one equatorial methyl group. | (C) The lower energy chair conformation contains one axial methyl group and one equatorial methyl group. | (D) The higher energy chair conformation contains two axial methyl groups. | (E) The lower energy chair conformation contains two axial methyl groups. |

11. Which is a measure of the randomness of a system?(A) entropy (B) enthalpy (C) free energy (D) halogenation (E) stoichiometry 

13. HBr can be added to an alkene in the presence of peroxides (ROOR). What function does the peroxide serve in this | reaction? (A) nucleophile (B) electrophile (C) radical chain initiator j (D) acid catalyst . (E) solvent |

14. Which of the following terms best describes the reactive nature of a Grignard reagent? (A) carbocation (B) free radical (C) electrophile (D) nucleophile (E) carbene

15. The mass spectrum of alcohols often fail to exhibit detectable M peaks but instead show relatively large_peaks. (A) M+l (B) M+2 (C) M-16 (D)M-17 (E) M-18

16. Absorption of what type of electromagnetic radiation results in transitions among allowed nuclear magnetic spin states? (A) X-rays (B) radio waves (C) microwaves (D) ultraviolet light (E) infrared light

17. For the reaction in which A and B react to form C，the following intial rate data were obtained. What is the rate law for the reaction? (A) Rate = k[A][B] (B) Rate = k[A]2[B] (C) Rate = k[A][B]2 (D) Rate - k[A]2[B]2 (E) Rate = k[A]3 

18. An NMR spectrometer that operates at a frequency of 60 MHz for C NMR spectra, operates at what frequency for H NMR spectra? (A) 15 MHz (B) 30 MHz (C) 60 MHz (D) 120 MHz (E) 240 MHz