47. Which of the following species is attacked by benzene in the electrophilic nitration reaction?
(A) HNO₃
(B) NO₂⁺
(C) NO₂
(D) NO⁺

43. Which of the following statements correctly pertains to a pair of enantiomers? (A) They rotate the plane of polarized light by exactly the same amount and in opposite directions. (B) They rotate the plane of polarized light by differing amounts and in opposite directions. (C) They rotate the plane of polarized light by differing amounts and in the same direction. (D) The have different melting points. 

44. Predict the specific rotation of the compound shown. (A) It is impossible to predict； it must be determined experimentally. (B) Because both asymmetric centers are R, the compound is dextrorotatory. (C) Because both asymmetric centers are S, the compound is levorotatory. (D) Zero； the compound is achiral.

45. What is the major difference between an antiaromatic and aromatic compound? (A) Only aromatic compounds follow Huckle's rule. (B) Antiaromatic compounds have at least one sp3 hybridized atom in the ring. (C) Antiaromatic compounds can assume a chair-like structure while aromatic compounds are nearly flat. (D) Aromatic compounds cannot have a charged atom in the structure.

46. Which of the following is an incorrect statement about the bromination of benzene by Br2 and FeBr3? (A) FeBr3 functions to increase the electrophilicity of Br2. (B) Formation of the sigma complex is the rate-determining step of the mechanism. (C) The carbanionic intermediate is resonance stabilized. (D) There is one carbon-containing intermediates in the mechanism.

48. Which of the following compounds will not undergo Friedel-Crafts acylation when treated with  CH3CH2COCl, AIC13?(A) toluene(B) p-xylene(C) benzophenone(D) ethoxybenzene

49. Which series of reagents would be required to perform the following synthesis? (A) 1. ClCH2CH2CH3, AlCl3 2. FeBr3, Br2 (B) 1. ClCOCH2CH3, AlCl3 2. FeBr3, Br2 (C) 1. ClCOCH2CH3, AlCl3 2. FeBr3, Br2 3. Zn(Hg), HCl (D) 1. ClCOCH2CH3, AlCl3 2. Zn(Hg), HCl 3. FeBr3, Br2

複選題50. What are the expected products of the reaction of PhOCH3 with concentrated HI? (A) phenol and methanol (B) phenol and iodomethane (C) iodobenzene and methanol (D) iodobenzene and iodomethane

51. Which of the following is produced by the reaction of (CH3CH2)2S with CH3CH2I? (A) CH3CH2CH2CH2I (B) (CH3CH2)3S+ I- (C) (CH3CH2)3S (D) CH3SCH2CH2CH3

52. Through what basic mechanism is 1-methylcyclohexanol converted to 1-bromo-1-methylcyclohexane upon treatment with HBr? (A) SN1(B) SN2(C) E1(D) E2

53. What is the major organic product of the following reaction? (A) (B) (C) (D) Both A and B