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Organic Chemistry, 9e (Wade) Chapter 6 Alkyl Halides; Nucleophilic Substitution 1) Which of the following best describes the carbon-chlorine bond of an alkyl chloride? A) nonpolar; no dipole B) polar; ?+ at carbon and ?- at chlorine C) polar; ?- at carbon and ?+ at chlorine D) ionic E) none of the above Answer: B Diff: 1 Section: 6.4 LO: 6.1 MCAT LO: MCAT6.1 2) Which of the following is classified as a vinylic halide? A) CH3CHCHOH B) CH3CHCHCl C) CH3CHCHCH2Cl D) CH3CH2CH2CH2Br E) BrCH2CHCH2 Answer: B Diff: 1 Section: 6.1 LO: 6.1 MCAT LO: MCAT6.1 3) The flame retardant below has been found to be an androgen agonist and may have a contribution to an increasing rate of occurrence of prostate cancer (J. Med. Chem. 2006, 7366). What is the correct term that describes the relative position of the bromides in this structure? A) geminal B) vinyl C) vicinal D) aryl Answer: C Diff: 1 Section: 6.2 LO: 6.1 GO: G2, G5 MCAT LO: MCAT6.1 4) What general classification is given to the molecule below? A) primary chloride B) secondary chloride C) tertiary chloride D) vinyl chloride E) benzyl chloride Answer: C Diff: 1 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 5) Provide the name of the bromoalkane shown below. Answer: 3-bromo-4-ethylheptane Diff: 1 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 6) Draw the structure of cis-1,3-dichlorocyclopentane. Answer: Diff: 1 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 7) Provide an acceptable name for CHCl3. Answer: chloroform or trichloromethane Diff: 1 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 8) Provide an acceptable name for CH3CH2CH2C(CH3)2I. Answer: 2-iodo-2-methylpentane Diff: 1 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 9) Provide an acceptable name for the compound shown below. Answer: cis-1, 2-dichlorocyclopentane Diff: 1 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 10) Provide the structure of isopropyl iodide. Answer: (CH3)2CHI Diff: 1 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 11) Which of the following is a secondary halide? A) ClCH2CH2C(CH3)3 B) ClCH2CH2CH(CH3)2 C) (CH3)2CClCH2CH3 D) (CH3)3CCHClCH3 E) ClCH2C(CH3)CH2CH3 Answer: D Diff: 1 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 12) Which of the following is a tertiary halide? A) ClCH2CH2C(CH3)3 B) ClCH2CH2CH(CH3)2 C) (CH3)2CClCH2CH3 D) (CH3)3CCHClCH3 E) ClCH2C(CH3)CH2CH3 Answer: C Diff: 1 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 13) Which of the following is a geminal dihalide? A) cis-1,2-dibromocyclopentane B) 3,3-dichloropentane C) trans-1,4-diiodocyclohexane D) isobutyl chloride E) 1,3-dibromoheptane Answer: B Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 14) Which of the following is a vicinal dihalide? A) cis-1,2-dibromocyclopentane B) 3,3-dichloropentane C) trans-1,4-diiodocyclohexane D) isobutyl chloride E) 1,3-dibromoheptane Answer: A Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 15) Which of the following is a secondary alkyl halide? A) methyl bromide B) isopropyl chloride C) t-butyl iodide D) propyl bromide E) isobutyl chloride Answer: B Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 16) Which of the following is a primary alkyl halide? A) methyl bromide B) isopropyl bromide C) t-butyl iodide D) cyclohexyl bromide E) isobutyl chloride Answer: E Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 17) What is the IUPAC name of the compound shown below? A) (1S,3S)-1,3-dichloro-1-ethyl-3-methylcyclopentane B) (1R,3S)-1,3-dichloro-1-methyl-3-ethylcyclopentane C) (1R,4S)-1,4-dichloro-1-ethyl-4-methylcyclopentane D) (1R,3S)-1,3-dichloro-1-ethyl-3-methylcyclopentane E) (1S,3R)-1,3-dichloro-3-ethyl-1-methylcyclopentane Answer: D Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 18) What is the IUPAC name of the compound shown below? A) (2R,3S,4S)-2-chloro-3,4-dibromo-3-methylhexane B) (2R,3S,4S)-3,4-dibromo-2-chloro-3-methylhexane C) (3S,4S,5S)-3,4-dibromo-5-chloro-4-methylhexane D) (2R,3R,4S)-3,4-dibromo-2-chloro-3-methylhexane E) (2R,3S,4R)-3,4-dibromo-2-chloro-3-methylhexane Answer: B Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 19) Provide an acceptable name for the compound shown below. Answer: 4-bromo-1,1-dimethylcyclohexane Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 20) Provide the structure of 1-bromo-3-methylhexane. Answer: CH3CH2CH2CH(CH3)CH2CH2Br Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 21) The following structure is a proteasome inhibitor that may find application in treating cervical cancer (J. Med. Chem. 2011, 449). The halides in this structure may be classified as ________ and ________. A) vicinal; vinyl B) vicinal; aryl C) vinyl; aryl D) vinyl; geminal Answer: B Diff: 2 Section: 6.2 LO: 6.1 GO: G5 MCAT LO: MCAT6.1 22) Name the haloalkane shown. Be sure to include the appropriate R or S description if needed. Answer: (3R,4R,6S)-4-ethyl-1,6-difluoro-3-methylheptane Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 23) Name the haloalkane shown. Be sure to include the appropriate R or S description if needed. Answer: (S)- 3-chloro-1,1-dimethylcyclohexane Diff: 2 Section: 6.2 LO: 6.1 MCAT LO: MCAT6.1 24) The term CFC is an abbreviation for ________. Answer: chlorofluorocarbon Diff: 1 Section: 6.3 LO: 6.1 MCAT LO: MCAT6.1 25) Which of the following best describes DDT? A) a chlorocarbon used to decaffeinate coffee beans B) a polybrominated organic compound used as a herbicide C) a Freon used as a foaming agent D) a mixed alkyl halide used as an anesthetic E) a polychlorinated organic compound used as an insecticide Answer: E Diff: 2 Section: 6.3 LO: 6.1 GO: G5 MCAT LO: MCAT6.1 26) Which of the following alkyl halides has the smallest molecular dipole moment? A) CH3F B) CH3Cl C) CH2I2 D) CH2Cl2 E) CF4 Answer: E Diff: 2 Section: 6.4 MCAT LO: MCAT6.4 27) Although F is more electronegative than Cl, the C-Cl bond has a larger dipole moment than the Explain. Answer: The bond dipole moment is determined by a product of the amount of charge separation and the distance over which the charge is separated, Although ? is larger in the the greater length of the ultimately makes its dipole moment larger. Diff: 3 Section: 6.4 MCAT LO: MCAT6.4 28) Among the following alkyl halides, choose the one with the lowest boiling point. A) t-butyl chloride B) n-butyl chloride C) t-butyl bromide D) n-butyl iodide E) t-butyl iodide Answer: A Diff: 2 Section: 6.5 LO: 6.1 MCAT LO: MCAT6.1 29) Arrange the following alkyl halides in order of increasing boiling point: CH3CH2Br, CH3CH2CH2Br, (CH3)2CHBr, CH3CH2F. Answer: CH3CH2F < CH3CH2Br < (CH3)2CHBr < CH3CH2CH2Br Diff: 2 Section: 6.5 LO: 6.1 MCAT LO: MCAT6.1 30) When water is shaken with dichloromethane, a two-phase system results. Which compound forms the upper phase? Explain. Answer: Water is less dense than dichloromethane and therefore forms the upper phase. Diff: 2 Section: 6.5 LO: 6.1 GO: G5 MCAT LO: MCAT6.1 31) When 2,2-dimethylbutane is subjected to free-radical chlorination, ________ distinct monochlorinated products are possible and ________ of these contain asymmetric carbon atoms. A) 4; 2 B) 5; 0 C) 3; 0 D) 5; 2 E) 4; 0 Answer: A Diff: 2 Section: 6.6 LO: 6.2 GO: G2 32) Draw two reasonable resonance structures and the hybrid of the intermediate formed in the following reaction. Answer: Free Radical mechanism at the allylic C's Diff: 2 Section: 6.6 LO: 6.2 MCAT LO: MCAT6.5 33) Provide the major organic product of the reaction below. Answer: Diff: 2 Section: 6.6 LO: 6.2 34) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 6.6 LO: 6.2 35) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 6.6 LO: 6.2 36) Draw the structures of the two major products formed in the following reaction. Indicate which of the two structures would be predicted to predominate under thermodynamic condition and explain why. Answer: Reactivity of allylic hydrogens due to resonance stability of the radical intermediate would result in the the formation of two major substitution products: 1 2 Product #2 (1-bromomethyl-cyclohexene) would be predicted to predominate in this reaction because it would form the more substituted alkene. However, radical characteristics on the secondary carbon may lead to a significant formation of product #1. Diff: 3 Section: 6.6 LO: 6.2 MCAT LO: MCAT6.5 37) Consider the reaction of (CH3)3CO- with iodomethane. Will the reaction rate increase, decrease, or remain the same if the concentration of iodomethane is increased? Explain. Answer: This is an SN2 reaction with a The reaction rate will increase as [CH3I] increases. Diff: 1 Section: 6.8 MCAT LO: MCAT6.3 38) What type of intermediate is present in the SN2 reaction of cyanide with bromoethane? A) carbocation B) free radical C) carbene D) carbanion E) This reaction has no intermediate. Answer: E Diff: 2 Section: 6.8 LO: 6.4 39) Provide a detailed, stepwise mechanism for the reaction below. (CH3)2CHCH2CH2CH2I + CN- ? (CH3)2CHCH2CH2CH2CH2CN + I- Answer: Diff: 2 Section: 6.8 LO: 6.4 40) Show how the following reaction might be constructed using an SN2 reaction by drawing structures for the starting materials. Answer: Diff: 2 Section: 6.9 LO: 6.3 GO: G2 41) Consider the substitution reaction shown below. By what mechanism will the reaction proceed? A) SN1 B) SN2 C) free radical reaction D) There is not enough information to tell. Answer: B Diff: 1 Section: 6.17 LO: 6.7 42) Provide the structure of the major organic product in the following reaction. (CH3)3N + CH3CH2CH2I ? Answer: [(CH3)3NCH2CH2CH3]+ I- Diff: 2 Section: 6.9 LO: 6.3 MCAT LO: MCAT6.2 43) Which of the following species is the least nucleophilic? A) H2O B) BF3 C) (CH3)3N D) CH3O- E) CN- Answer: B Diff: 2 Section: 6.10 LO: 6.6 44) Which of the following compounds is the most nucleophilic? A) CH3SH B) CH3OH C) H2O D) CH3CO2H E) BF3 Answer: A Diff: 2 Section: 6.10 LO: 6.6 45) Name one factor that is favorable for nucleophilicity but not for basicity. Answer: polarizability Diff: 2 Section: 6.10 46) Arrange the following species in order of increasing nucleophilicity: CH3CH2S-, CH3CH2O-, (CH3)3CO-, (CH3)3COH. Answer: (CH3)3COH < (CH3)3CO- < CH3CH2O- < CH3CH2S- Diff: 2 Section: 6.10 LO: 6.6 47) Which halide is a better nucleophile, iodide or fluoride? Explain. Answer: The iodide ion is the better nucleophile. The larger size of this ion renders its electron cloud more polarizable. Diff: 2 Section: 6.10 LO: 6.6 48) Which is more nucleophilic, t-butoxide or ethoxide? Explain. Answer: Ethoxide is the better nucleophile. The steric bulk of t-butoxide decreases its effectiveness as a nucleophile. Diff: 2 Section: 6.10 LO: 6.6 49) Rank the species below in order of increasing nucleophilicity in hydroxylic solvents: CH3CO2-, CH3S-, HO-, H2O. Answer: H2O < CH3CO2- < HO- < CH3S- Diff: 2 Section: 6.10 LO: 6.6 50) Which of the following factors is favorable for nucleophilicity but not basicity? A) highly polarizable B) low electronegativity C) negatively charged D) sterically hindered Answer: A Diff: 2 Section: 6.10 LO: 6.6 GO: G2 51) Which of the following solvents could be described as polar and protic? A) ethanol B) acetonitrile C) dimethylformamide D) acetone E) 18-crown-6 Answer: A Diff: 3 Section: 6.10 LO: 6.2 52) What type of solvent is best for SN2 reactions which employ anionic nucleophiles: polar, protic solvents; polar, aprotic solvents; or nonpolar solvents? Explain. Answer: Polar, aprotic solvents are best. These solvents have strong dipole moments to enhance solubility of the anionic species but lack the ability to solvate the anion by hydrogen bonding. Diff: 3 Section: 6.10 LO: 6.6 53) Which of the following compounds will undergo an SN2 reaction most readily? A) (CH3)3CCH2I B) (CH3)3CCl C) (CH3)2CHI D) (CH3)2CHCH2CH2CH2I E) (CH3)2CHCH2CH2CH2Cl Answer: D Diff: 2 Section: 6.11 LO: 6.6 54) Which of the following alkyl chlorides will undergo SN2 reaction most readily? A) 1-chloro-4-methylpentane B) 2-chloro-4-methylpentane C) 2-chloro-3-methylpentane D) 3-chloro-2-methylpentane E) 2-chloro-2-methylpentane Answer: A Diff: 2 Section: 6.11 LO: 6.6 55) Arrange the following substrates in order of their increasing SN2 reactivity with NaCN: bromoethane, 1-chloro-3,3-dimethylpentane, 1-chloro-2,2-dimethylpentane, and 2-bromo-2-methylpentane. Answer: 2-bromo-2-methylpentane < 1-chloro-2,2-dimethylpentane < 1-chloro-3,3-dimethylpentane < bromoethane Diff: 2 Section: 6.11 LO: 6.6 56) List the following bromides in order of their increasing reactivity as substrates in SN2 reactions: PhBr, PhCH2Br, and PhCH(CH3)Br. Answer: PhBr < PhCH(CH3)Br < PhCH2Br Diff: 2 Section: 6.11 LO: 6.6 57) List the following alkyl halides in order of their increasing reactivity as substrates in SN2 reactions: 2-chlorobutane, 2-iodobutane, and 1-iodobutane. Answer: 2-chlorobutane < 2-iodobutane < 1-iodobutane Diff: 2 Section: 6.11 LO: 6.6 58) Do all primary iodides react with N3- at the same rate via the SN2 mechanism? Explain. Answer: No, not all primary alkyl react with N3- at the same rate via the SN2 mechanism. Some primary iodides are more hindered than others. (CH3)3CCH2I and CH3CH2I are both primary, but (CH3)3CCH2I is significantly more hindered. Additionally, some primary iodides have increased activity due to a benzylic or allylic positioning. Diff: 2 Section: 6.11 LO: 6.6 GO: G2 59) Do all primary alkyl iodides undergo SN2 reactions with sodium cyanide in DMSO at identical rates? Explain. Answer: No. All primary iodides are not equally accessible to attack by the CN-. Steric hindrance varies among primary iodides. Diff: 2 Section: 6.11 LO: 6.6 GO: G2 60) Which of the following alkyl chlorides would undergo substitution most rapidly when treated with or Provide the structure of the substitution product. Answer: CH3CH2CCH Diff: 2 Section: 6.11 LO: 6.6 61) Show the best way to prepare CH3OCH(CH3)2 by an SN2 reaction. Answer: CH3I + NaOCH(CH3)2 Diff: 2 Section: 6.11 LO: 6.2 62) Which of the following statements describe a favorable attribute of a leaving group? (More than one answer is possible.) A) The leaving group should be highly polarizable. B) The lower the electronegativity of the leaving group the better. C) Good leaving groups need to have low steric hindrance. D) The departed leaving group should have low basicity. Answer: A, D Diff: 2 Section: 6.11 LO: 6.6 GO: G2 63) Which of the following alkyl halides reacts most rapidly via an SN2 reaction with NaCN? A) 1-iodohexane B) 1-fluorohexane C) (R)-2-bromohexane D) iodocyclohexane E) 1-iodo-1-methylcyclohexane Answer: A Diff: 2 Section: 6.11 LO: 6.6 64) SN2 reactions take place with ________ of stereochemistry at the center undergoing substitution. Answer: inversion Diff: 1 Section: 6.12 LO: 6.3 65) Complete the following SN2 reaction by providing structures for the necessary starting materials. Answer: Diff: 2 Section: 6.12 LO: 6.3 MCAT LO: MCAT6.2 66) Provide the major organic product of the SN2 reaction below. Answer: Diff: 2 Section: 6.12 LO: 6.3 MCAT LO: MCAT6.2 67) Provide the major organic product of the reaction below. Answer: Diff: 2 Section: 6.12 LO: 6.2 MCAT LO: MCAT6.3 68) Provide the major organic product of the reaction below. Answer: Diff: 2 Section: 6.12 LO: 6.2 MCAT LO: MCAT6.3 69) Provide the structure of the major organic product which results when (S)-2-iodopentane is treated with KCN in DMF. Answer: Diff: 2 Section: 6.12 LO: 6.3 MCAT LO: MCAT6.2 70) Provide the structure of the major organic product in the following reaction. Answer: Diff: 2 Section: 6.12 LO: 6.3 MCAT LO: MCAT6.2 71) Which of the compounds below undergoes solvolysis in aqueous ethanol most rapidly? A) cyclohexyl bromide B) methyl iodide C) isopropyl chloride D) 3-chloropentane E) 3-iodo-3-methylpentane Answer: E Diff: 2 Section: 6.13 LO: 6.6 72) Which of the following alkyl bromides undergoes solvolysis in aqueous methanol most rapidly? A) PhCHBrCH3 B) (CH3)2CHCH2CH2Br C) (CH3)2CHCH2CHBrCH3 D) CH3CH2CH2CH2Br E) PhBr Answer: A Diff: 2 Section: 6.13 LO: 6.6 73) Arrange the following compounds in order of increasing reactivity toward ethanol solvolysis: t-butyl bromide, t-butyl iodide, isopropyl chloride, methyl iodide. Answer: methyl iodide < isopropyl chloride < t-butyl bromide < t-butyl iodide Diff: 2 Section: 6.13 LO: 6.6 74) List the following bromides in order of their increasing reactivity as substrates in SN1 reactions: PhBr, PhCH2Br, and PhCH(CH3)Br. Answer: PhBr < PhCH2Br < PhCH(CH3)Br Diff: 2 Section: 6.13 LO: 6.6 75) List the following bromides in order of their increasing reactivity as substrates in SN1 reactions: 2-chlorobutane, 2-iodobutane, and 1-iodobutane. Answer: 1-iodobutane < 2-chlorobutane < 2-iodobutane Diff: 2 Section: 6.13 LO: 6.6 76) List the following bromides in order of their increasing reactivity as substrates in SN1 reactions: 1-iodo-1-ethylcyclopentane, chlorocyclopentane, and iodocyclopentane. Answer: chlorocyclopentane < iodocyclopentane < 1-iodo-1-ethylcyclopentane Diff: 2 Section: 6.13 LO: 6.6 77) Draw the highest energy transition state in the solvolysis of (CH3)3CI in CH3OH. Answer: Diff: 2 Section: 6.13 LO: 6.4 GO: G7 78) List the following compounds in order of increasing reactivity in an SN1 reaction. CH3Br, CH3CH2CH2I, (CH3)3CI, CH3CHBrCH3, CH3CHICH3 Answer: CH3Br < CH3CH2CH2I < CH3CHBrCH3 < CH3CHICH3 < (CH3)3CI Diff: 2 Section: 6.13 LO: 6.6 79) Which of the following alkyl halides reacts most rapidly via an SN1 solvolysis reaction in hot methanol? A) 1-iodohexane B) 1-fluorohexane C) (R)-2-bromohexane D) iodocyclohexane E) 1-iodo-1-methylcyclohexane Answer: E Diff: 2 Section: 6.13 LO: 6.6 GO: G2 80) Rank the following molecules in order of increasing relative rate of SN1 solvolysis with methanol and heat (slowest to fastest reacting). A) 3 < 2 < 4 < 5 < 1 B) 2 < 3 < 4 < 1 < 5 C) 5 < 4 < 3 < 2 < 1 D) 2 < 3 < 4 < 5 < 1 E) 1 < 2 < 5 < 4 < 3 Answer: B Diff: 3 Section: 6.13 LO: 6.6 GO: G2 81) When t-butyl chloride undergoes solvolysis in a solvent mixture composed of 70% water/30% acetone, the reaction rate is slower than when the same compound is solvolyzed in 80% water/20% acetone. Explain. Answer: This is purely a solvent effect. The greater the percentage of water in this solvent mixture, the more polar the solvent. The more polar the solvent, the more easily solvated the developing carbocation and the more rapidly it is formed. Diff: 3 Section: 6.13 LO: 6.6 GO: G2 82) If the absolute configuration at an asymmetric carbon does not change during the course of a reaction, the reaction is said to occur with ________ of stereochemistry. Answer: retention Diff: 1 Section: 6.14 LO: 6.3 MCAT LO: MCAT6.2 83) When a SN1 reaction of R-2-iodobutane takes place in hot methanol, the product ________. A) is chiral B) will rotate plane polarized light C) is racemic D) will undergo a hydride shift E) none of the above Answer: C Diff: 2 Section: 6.14 LO: 6.2 84) When trans-1-iodo-4-methylcyclohexane is heated in methanol, the product mixture is primarily ________. A) a single, chiral compound B) a mixture of diasteromeric ethers C) a mixture of diasteromeric alcohols D) a single, chiral alcohol E) a single, chiral ether Answer: B Diff: 2 Section: 6.14 LO: 6.3 MCAT LO: MCAT6.2 85) Provide the structure of the major organic products which result in the reaction below. Answer: Diff: 2 Section: 6.14 LO: 6.3 MCAT LO: MCAT6.2 86) SN1 reactions usually proceed with ________. A) equal amounts of inversion and retention at the center undergoing substitution B) slightly more inversion than retention at the center undergoing substitution C) slightly more retention then inversion at the center undergoing substitution D) complete inversion at the center undergoing substitution E) complete retention at the center undergoing substitution Answer: B Diff: 3 Section: 6.14 LO: 6.3 MCAT LO: MCAT6.2 87) Provide two circumstances under which solvolysis of a chiral alkyl halide would not result in the generation of a mixture of enantiomeric products. Answer: Choose two from among: (i) leaving group not bound to stereocenter (ii) rearrangement yields a carbocation in which two groups bound to the cationic center are the same (iii) the molecule contains at least one additional stereocenter which is unaffected by the ionization (iv) rearrangement ultimately results in a meso compound Diff: 3 Section: 6.14 LO: 6.4 88) Which of the cations below would be subject to a structural rearrangement? A) 1 B) 3 C) 1, 2, & 3 D) 2 & 3 Answer: B Diff: 2 Section: 6.15 LO: 6.5 89) Which of the following alkyl halides is most likely to undergo rearrangement in an SN1 reaction? A) 3-bromopentane B) 2-chloro-3,3-dimethylpentane C) 3-chloropentane D) bromocyclohexane E) 1-bromo-4-methylcyclohexane Answer: B Diff: 2 Section: 6.15 LO: 6.5 90) Which of the following alkyl chlorides is least likely to undergo rearrangement during a solvolysis reaction? A) 2-chloro-4-methylpentane B) 2-chloro-3-methylpentane C) 2-chloro-2-methylpentane D) cis-1-chloro-2-ethylcyclohexane E) trans-1-chloro-2-ethylcyclohexane Answer: C Diff: 2 Section: 6.15 LO: 6.5 91) A sample of 1-chloro-1-phenylethane with an [?]25D of -94.8° is reacted with NH3 in methanol/water solvent. The major substitution product of the reaction is 1-phenyl-1-ethylamine with an [?]25D of -8.6°. Given that optically pure (R) 1-chloro-1-phenylethane has a specific rotation of -109.0° and that optically pure (R) 1-phenyl-1-ethylamine has a specific rotation of +39.3°, which of the following statements best describes this reaction? A) Net inversion 25% with 75% racemization — SN1 mechanism B) Net inversion 12% with 88% racemization — SN1 mechanism C) Net inversion 75% with 25% racemization — SN2 mechanism D) Net inversion 12% with 88% racemization — SN2 mechanism E) Net inversion 88% with 12% racemization — SN2 mechanism Answer: A Diff: 3 Section: 6.15 LO: 6.7 GO: G4 MCAT LO: MCAT5.3 92) Predict the structure of the expected product for the following reaction. Answer: Diff: 3 Section: 6.15 LO: 6.3, 6.5 93) Provide the major organic product of the reaction below and a detailed, stepwise mechanism which accounts for its formation. Answer: Diff: 3 Section: 6.15 LO: 6.3, 6.5 94) Provide the structure of the major organic product which results in the following reaction. Answer: Diff: 3 Section: 6.15 LO: 6.3, 6.5 MCAT LO: MCAT6.2 95) Which of the following statements correctly describe(s) E1 reactions of alkyl halides (RX)? I. Rate = k[base] II. Rate = k[base][RX] III. Rate = k[RX] IV. The reactions occur in two or more distinct steps. V. Rearrangements are sometimes seen. A) II and IV B) III and V C) I, IV, and V D) I only E) III, IV, and V Answer: E Diff: 2 Section: 7.10 LO: 6.3 MCAT LO: MCAT6.3 96) Why does CH2CHCHBrCH3 undergo solvolysis much more rapidly than 2-bromobutane? Answer: The intermediate carbocation is resonance stabilized. Diff: 3 Section: 6.13 LO: 6.6 MCAT LO: MCAT6.5 97) When 1-bromo-2, 2-dimethylcyclopentane is heated in ethanol, one of the products which results is shown below. Provide a detailed, stepwise mechanism for the production of this compound, and give the name of the mechanism by which it is produced. Answer: Diff: 3 Section: 7.10 LO: 6.4 GO: G2 98) Provide a step-by-step mechanism for the reaction below. Include all intermediates, formal charges and correct arrow pushing of electrons. Answer: Diff: 3 Section: 7.10 LO: 6.4 GO: G2 99) What is Zaitsev's rule? Answer: In elimination reactions, the most highly substituted alkene product is the major product. Diff: 2 Section: 7.11 LO: 6.2 100) Dehydration of 1-butanol with concentrated sulfuric acid at 140?C results in the formation of mainly trans-2-butene. According to these results, which of the following conclusions might be valid? A) The reaction undergoes an E2-type elimination mechanism. B) The reaction follows a new mechanism involving the formation of a carbanion intermediate. C) The reaction undergoes an E1-type elimination mechanism in conjunction with a hydride shift. D) The reaction undergoes an E2-type elimination mechanism in conjunction with a methyl shift. E) The reaction undergoes an E1-type elimination mechanism with no shifting. Answer: C Diff: 3 Section: 7.11 LO: 7.4 GO: G7 MCAT LO: MCAT6.2 101) How many distinct alkene products are possible, including stereoisomers, when the alkyl iodide below undergoes E2 elimination? A) 1 B) 2 C) 3 D) 4 E) 5 Answer: E Diff: 2 Section: 7.12 LO: 7.6 MCAT LO: MCAT6.2 102) Which of the following alkyl halides can produce only a single alkene product from when treated with sodium methoxide? A) 2-chloro-2-methylpentane B) 3-chloro-3-ethylpentane C) 3-chloro-2-methylpentane D) 2-chloro-4-methylpentane E) 2-chloro-3-ethylpentane Answer: B Diff: 2 Section: 7.12 LO: 7.6 GO: G2 MCAT LO: MCAT6.2 103) How many distinct alkene products results when 1-bromo-1-ethylcyclopentane is treated with NaOCH3? A) 1 B) 2 C) 3 D) 4 Answer: B Diff: 2 Section: 7.12 LO: 7.4 MCAT LO: MCAT6.2 104) Provide the major organic product of the reaction below. Answer: Diff: 2 Section: 7.12 LO: 7.4 MCAT LO: MCAT6.2 105) Provide the major organic product of the reaction below. Answer: Diff: 2 Section: 7.12 LO: 7.4 MCAT LO: MCAT6.2 106) Provide the major organic product of the reaction below. Answer: Diff: 2 Section: 7.12 LO: 7.4 MCAT LO: MCAT6.2 107) Provide a structure for the major substitution and major elimination product resulting from the reaction below. Answer: Diff: 2 Section: 7.17 LO: 7.4 MCAT LO: MCAT6.2 108) Provide the structure of the major alkene product of the reaction below. Answer: Diff: 2 Section: 6.19 LO: 7.4 MCAT LO: MCAT6.2 109) Provide the major organic product of the reaction below. Answer: Diff: 2 Section: 7.12 LO: 7.4 MCAT LO: MCAT6.2 110) Provide a series of synthetic steps by which (CH3)2CCH2 could be prepared from 2-methylpropane. Answer: 1) Br2, h? 2) NaOCH3, CH3OH Diff: 2 Section: 7.12 LO: 7.7 GO: G7 111) Provide the structure of the major organic product which results when 2-bromo-2-methylbutane is treated with sodium ethoxide. Answer: Diff: 2 Section: 7.12 LO: 7.4 GO: G7 MCAT LO: MCAT6.2 112) When 1-iodo-1-methylcyclohexane is treated with NaOCH2CH3, the more highly substituted alkene product predominates. When KOC(CH3)3 is used instead, the less highly substituted alkene product predominates. Offer an explanation. Answer: The unhindered ethoxide produces the more stable alkene product (ie, the more highly substituted alkene possible). When the bulky t-butoxide is used, the most accessible hydrogen is removed. This results in the least highly substituted alkene possible. Diff: 3 Section: 7.13 LO: 7.4 GO: G2 MCAT LO: MCAT6.2 113) Provide the major organic product of the reaction below. Answer: Diff: 2 Section: 7.14 LO: 7.6 GO: G2 MCAT LO: MCAT6.2 114) Provide the structure of the major organic product which results in the following reaction. Answer: Diff: 2 Section: 7.15 LO: 7.6 MCAT LO: MCAT6.2 115) Provide the structure of the major organic product which results in the following reaction. Answer: Diff: 2 Section: 7.15 LO: 7.6 MCAT LO: MCAT6.2 116) Propose a mechanism with a hydride shift for the solvolysis reaction below. Answer: Diff: 3 Section: 6.15 LO: 6.4 GO: G2 117) Provide a structure for the major substitution and elimination product of the following reaction. Answer: Diff: 3 Section: 7.17 LO: 7.6 GO: G2 MCAT LO: MCAT6.2 118) When (cis)-1-bromo-2 methylcyclohexane is treated with methanol and heat, four different products are formed — two by substitution and two by elimination. Which of the following conditions would change the outcome of this reaction by promoting the production of 3-methylhexene as the major product? A) KOH, ethanol and heat B) water/acetone and heat C) tert-butoxide/tert-butyl alcohol D) tert-butyl alcohol and heat E) methoxide/methanol Answer: C Diff: 3 Section: 7.17 LO: 7.6 GO: G2 MCAT LO: MCAT6.2 119) Draw a chair conformation of the starting substituted cyclohexane molecule with the bromine in the axial position. Using this model, predict the major elimination product of this reaction. Answer: Diff: 3 Section: 7.15 LO: 7.6 GO: G7 MCAT LO: MCAT6.2 120) Which diastereomer of 1-bromo-4-t-butylcyclohexane, the cis or the trans, undergoes elimination more rapidly when treated with sodium ethoxide? Explain your answer. Answer: The cis isomer reacts more quickly. An axial orientation of the C—Br bond is required for E2 in six-membered ring systems. In order for this to occur in the trans isomer, the bulky t-butyl group must also assume an axial orientation; this requires substantial energy of activation. Diff: 3 Section: 7.15 LO: 7.6 GO: G7 MCAT LO: MCAT6.2 121) Provide the structure of the major organic product in the following reaction. Answer: Diff: 3 Section: 7.14 LO: 7.6 GO: G2 MCAT LO: MCAT6.2 122) Provide the structure of the major organic product in the following reaction. Answer: Diff: 3 Section: 7.14 LO: 7.6 GO: G2 MCAT LO: MCAT6.2 123) Which of the following mechanisms (SN1, SN2, E1, E2) feature(s) a carbocation intermediate? A) SN1 only B) SN2 only C) E1 only D) E2 only E) both SN1 and E1 Answer: E Diff: 1 Section: 7.17 LO: 6.9 GO: G2 MCAT LO: MCAT6.2 124) In which of the following mechanisms (SN1, SN2, E1, E2) are alkenes the major reaction products? A) SN1 only B) SN2 only C) E1 only D) E2 only E) both E1 and E2 Answer: E Diff: 1 Section: 7.17 LO: 6.9 GO: G2 MCAT LO: MCAT6.2 125) Predict the most likely mechanism for the reaction shown below. A) SN1 B) SN2 C) E1 D) E2 E) E1cb Answer: A Diff: 2 Section: 7.17 LO: 6.9 GO: G7 MCAT LO: MCAT6.2 126) Predict the most likely mechanism for the reaction shown below. A) SN1 B) SN2 C) E1 D) E2 E) E1cb Answer: D Diff: 2 Section: 7.17 LO: 6.9 GO: G7 MCAT LO: MCAT6.2 127) Predict the two most likely mechanisms for the reaction of 2-iodohexane with potassium hydroxide. A) SN1 and SN2 B) E1 and E2 C) SN2 and E2 D) E1 and SN1 Answer: C Diff: 1 Section: 7.17 LO: 6.9 GO: G7 MCAT LO: MCAT6.2 128) Predict the two most likely mechanisms that occur when iodocyclohexane is heated in methanol. A) SN1 and SN2 B) E1 and E2 C) SN2 and E2 D) E1 and SN1 Answer: D Diff: 1 Section: 7.17 LO: 6.9 GO: G7 MCAT LO: MCAT6.2 129) The major product from the reaction of 2-chloro-2-methylpentane with sodium ethoxide in ethanol results from which of the following mechanistic pathways? A) SN1 B) SN2 C) E1 D) E2 E) Ecb Answer: D Diff: 1 Section: 7.17 LO: 6.9 GO: G7 MCAT LO: MCAT6.2 130) One product which results when 2-chloro-2-methylpentane is heated in ethanol is an ether. From which mechanistic pathway does this ether arise? A) SN1 B) SN2 C) E1 D) E2 E) E1cb Answer: A Diff: 2 Section: 7.17 LO: 6.9 GO: G7 MCAT LO: MCAT6.2 131) When 3-iodo-3-ethylpentane is treated with sodium methoxide in methanol, the major organic product is an ________ that is generated through an ________ mechanism. A) ether; SN1 B) ether; SN2 C) ether; E1 D) alkene; E2 E) alkene; E1 Answer: D Diff: 2 Section: 7.17 LO: 6.9 GO: G7 MCAT LO: MCAT6.2 132) When 3-iodo-3-ethylpentane is heated in methanol, the major organic product is an ________ that is generated through an ________ mechanism. A) ether; SN1 B) ether; SN2 C) ether; E1 D) alkene; E2 E) alcohol; E1 Answer: A Diff: 2 Section: 7.17 LO: 6.9 GO: G7 MCAT LO: MCAT6.2 133) Which of the following carbocations is likely to undergo a hydride shift? A) I B) II C) III D) IV E) II and IV F) II and III Answer: E Diff: 1 Section: 6.15 LO: 6.5 GO: G2 134) Circle the protic solvents. Answer: Diff: 1 Section: 6.10 GO: G2 135) Circle the aprotic solvents. Answer: Diff: 1 Section: 6.10 GO: G2 136) Rank the following compounds in order of increasing reactivity in an SN2 reaction. (Fastest is first, slowest is last.) A) III > I > II > IV B) II > IV > I > III C) IV > II > I > III D) IV > II > III > I Answer: C Diff: 1 Section: 6.11 LO: 6.6 GO: G2 137) Consider the substitution reaction shown below. By what mechanism will the reaction proceed? A) SN1 B) SN2 C) Free radical reaction D) There is not enough information to tell. Answer: A Diff: 1 Section: 6.16 LO: 6.7 138) Consider the substitution reaction shown below. By what mechanism will the reaction proceed? A) SN1 B) SN2 C) Free radical reaction D) There is not enough information to tell. Answer: B Diff: 2 Section: 6.16 LO: 6.7 1