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

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 

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

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 |

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

19. How many pairs of degenerate n molecular orbitals are found in benzene? (A) 6 (B) 5 (C) 4 (D) 3 (E) 2

20. Nitrogen's lone pair electrons occupy what type of orbital in pyridine? (A) s (B) sp (C) sp2 (D) sp3 (E) p