Package Title: Solomons Test Bank Course Title: Solomons 11e Chapter Number: 15 Question Type: Multiple Choice 1) Which of these is the rate-determining step in the nitration of benzene? a) Protonation of nitric acid by sulfuric acid b) Protonation of sulfuric acid by nitric acid c) Loss of a water molecule by the protonated species to produce the nitronium ion d) Addition of the nitronium to benzene to produce the arenium ion e) Loss of a proton by the arenium ion to form nitrobenzene Answer: D Topic: Mechanisms and Intermediates Section: 15.2 Difficulty Level: Medium 2) Which of these is the rate-determining step in the sulfonation of benzene? a) Formation of SO3 from sulfuric acid b) Protonation of SO3 sulfuric acid c) Addition of SO3H+ to benzene to form the arenium ion d) Loss of a proton from the arenium ion to form benzenesulfonic acid e) None of these choices Answer: C Topic: Mechanisms and Intermediates Section: 15.2 Difficulty Level: Medium 3) Which of these is the rate-determining step in the bromination of benzene? a) Complexation of bromine with the iron(III) bromide catalyst b) Formation of Br+ ion c) Addition of Br+ to benzene to form the arenium ion d) Loss of a proton from the arenium ion to form bromobenzene e) None of these choices Answer: C Topic: Mechanisms and Intermediates Section: 15.2 Difficulty Level: Medium 4) Which of the following structures contribute(s) to the resonance hybrid of the intermediate formed when bromobenzene undergoes para-chlorination? : Br : : Br + : Br : : Br : + + + H Cl H Cl H Cl H Cl I II III IV a) I b) II c) III d) IV e) All of these choices Answer: E Topic: Mechanisms and Intermediates Section: 15.11 Difficulty Level: Medium 5) Which of the following structures contribute(s) to the resonance hybrid of the intermediate formed when chlorobenzene undergoes para-chlorination? : Cl : : Cl + : Cl : : Cl : + + + H Cl H Cl H Cl H Cl I II III IV a) I b) II c) III d) IV e) All of these choices Answer: E Topic: Mechanisms and Intermediates Section: 15.11 Difficulty Level: Medium 6) Which of the following structures contribute(s) to the resonance hybrid of the intermediate formed when acetanilide undergoes para-bromination? +NCOCH :NHCOCH3 : NHCOCH3 : NHCOCH3 + + + H Br H Br H Br H Br I II III IV a) I b) II c) III d) IV e) All of these choices Answer: E Topic: Mechanisms and Intermediates Section: 15.11 Difficulty Level: Medium 7) Which of the following contributors to the resonance stabilized hybrid formed when aniline undergoes para-chlorination would be exceptionally stable? +NH2 : NH2 : NH2 : NH2 + + + H Cl H Cl H Cl H Cl I II III IV a) I b) II c) III d) IV e) None of these choices Answer: B Topic: Mechanisms and Intermediates Section: 15.11 Difficulty Level: Medium 8) Consider the structures given below Which of them would be a relatively stable contributor to the hybrid formed when toluene undergoes para bromination? a) I b) II c) III d) IV e) V Answer: C Topic: Mechanisms and Intermediates Section: 15.11 Difficulty Level: Medium 9) Which of the following structures does not contribute to the resonance hybrid of the intermediate formed when nitrobenzene undergoes meta-chlorination? :O : O: : O : O: : O : O: N N + H Cl I + N +H H Cl II Cl III a) I b) II c) III d) None of these contribute e) All of these contribute Answer: E Topic: Mechanisms and Intermediates Section: 15.11 Difficulty Level: Medium 10) Consider the resonance forms shown for the arenium ionformed from the bromination of acetanilide Which resonance form contributes most to the overall resonance hybrid? H I Br O HN HN HN Br O O O H II Br HN H H Br IV III a) I b) II c) III d) IV e) All contribute equally Answer: C Topic: Mechanisms and Intermediates Section: 15.11 Difficulty Level: Medium 11) Consider the resonance forms shown for the arenium ionformed from the bromination of acetanilide Which resonance form contributes most to the overall resonance hybrid? a) I b) II c) III d) IV e) All contribute equally Answer: D Topic: Mechanisms and Intermediates Section: 15.11 Difficulty Level: Medium 12) The electrophilic bromination or chlorination of benzene requires, in addition to the halogen: a) a hydroxide ion b) a Lewis base c) a Lewis acid d) peroxide e) ultraviolet light Answer: C Topic: Other EAS Considerations Section: 15.3 Difficulty Level: Easy 13) In electrophilic aromatic substitution, the attacking species (the electrophile) necessarily is a: a) neutral species b) positively charged species c) lewis acid d) proton e) carbocation Answer: C Topic: Other EAS Considerations Section: 15.2 Difficulty Level: Medium 14) Which of these liquids would be unsuitable as an inert solvent for a Friedel-Crafts reaction? a) Chlorobenzene b) Nitrobenzene c) Acetophenone d) (Trifluoromethyl) benzene e) All of these choices could be used Answer: A Topic: Other EAS Considerations Section: 15.8 Difficulty Level: Medium 15) Undesired polysubstitution of an aromatic nucleus is most likely to be encountered in the case of: a) Friedel-Crafts alkylation b) Friedel-Crafts acylation c) Nitration d) Sulfonation e) Chlorination Answer: A Topic: Other EAS Considerations Section: 15.8 Difficulty Level: Medium 16) This substituent deactivates the benzene ring towards electrophilic substitution but directs the incoming group chiefly to the ortho and para positions a) -OCH2CH3 b) -NO2 c) -F d) -CF3 e) -NHCOCH3 Answer: C Topic: Other EAS Considerations Section: 15.10 and 15.11 Difficulty Level: Medium 17) This molecule does not normally participate as a reactant in a Friedel-Crafts reaction a) Benzene b) Chlorobenzene c) Nitrobenzene d) Toluene e) tert-Butylbenzene Answer: C Topic: Other EAS Considerations Section: 15.8 Difficulty Level: Medium 18) Which one of these molecules can be a reactant in a Friedel-Crafts reaction? a) Aniline b) Nitrobenzene c) Chloroethene d) Bromobenzene e) p-Bromonitrobenzene Answer: D Topic: Other EAS Considerations Section: 15.8 Difficulty Level: Medium 19) Which one of these molecules can be a reactant in a Friedel-Crafts reaction? a) Aniline b) Benzenesulfonic acid c) Chloroethene d) Bromobenzene e) p-Bromonitrobenzene Answer: D Topic: Other EAS Considerations Section: 15.8 Difficulty Level: Medium 20) Which reagent would you use as the basis for a simple chemical test that would distinguish between toluene and vinylbenzene (C6H5CH=CH2)? a) NaOH/H2O b) Br2/CCl4 c) NaBH4 d) HCl/H2O e) NaI in acetone Answer: B Topic: Functional Group Tests Sections: 14.2, 14.3 and 15.3 Difficulty Level: Medium 21) Which reagent or test could you use to distinguish between phenylacetylene and vinylbenzene? a) NaOH/H2O b) Br2/CCl4 c) IR Spectroscopy d) CrO3/H2SO4 e) Concd H2SO4 Answer: C Topic: Nomenclature, Functional Group Tests Section: 14.2, 14.11 and 15.3 Difficulty Level: Medium 22) What is the chief product of the Friedel-Crafts alkylation of benzene with 1-butene and HF? a) butylbenzene b) 2-phenylbutane c) 2-methyl-1-phenylpropane d) t-butylbenzene e) 2,2-diphenylbutane Answer: B Topic: Nomenclature, Reaction Products Section: 14.2 and 15.6 Difficulty Level: Hard 23) What is the chief product of the Friedel-Crafts alkylation of benzene with 1-butene and AlCl3? a) butylbenzene b) 2-phenylbutane c) 2-methyl-1-phenylpropane d) t-butylbenzene e) 2,2-diphenylbutane Answer: B Topic: Nomenclature, Reaction Products Section: 14.2 and 15.6 Difficulty Level: Hard 24) A mixture of chlorobenzene (1 mol) and acetanilide (1mol) is allowed to react with Br2 (0.5 mol) in the presence of trace amounts of FeBr3 What is the principal product of the competing reactions? a) 1-bromo-4-chlorobenzene b) 1-bromo-2-chlorobenzene c) 1-bromo-3-chlorobenzene d) 4-bromoacetanilide e) 3-bromoacetanilide Answer: D Topic: Nomenclature, Reaction Products Section: 14.2, 15.3, and 15.8 Difficulty Level: Hard 25) A mixture of chlorobenzene (1 mol) and anisole (1mol) is allowed to react with Br2 (0.5 mol) in the presence of trace amounts of FeBr3 What is the principal product of the competing reactions? a) 1-bromo-4-chlorobenzene b) 1-bromo-2-chlorobenzene c) 1-bromo-3-chlorobenzene d) 4-bromoanisole e) 3-bromoanisole Answer: D Topic: Nomenclature, Reaction Products Section: 14.2, 15.3, and 15.8 Difficulty Level: Hard 26) Which of the following reactions could be used to synthesize tert-butylbenzene? a) C6H6 + CH2=C(CH3)2 H2SO4 10 H E ‡ + ‡ + H N N E Ea H Ea P.E E + N Reaction Progress Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 191) Using a potential energy diagram, explain/illustrate the preferential formation of the nitrated product instead of the nitrated product in the electrophilic aromatic nitration of naphthalene NO2 NO2 NO2+ instead of (-H+) Answer: The substitution product is favored since it comes from the arenium ion intermediate that is lower in energy/more stable (possesses two benzylic type resonance forms vs only one for the substituted product), and hence will form faster 105 Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 192) Using a potential energy diagram, explain/illustrate the preferential formation of the substituted product instead of the product in the electrophilic aromatic substitution of furan E E+ O instead of (-H+) E O O Answer: The substitution product is favored since it comes from the arenium ion intermediate that is lower in energy/more stable (possesses three resonance forms vs only two for the substituted product), and hence will form faster 106 Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 193) Using a potential energy diagram, explain/illustrate the preferential formation of the substituted product instead of the product in the electrophilic aromatic substitution of pyrrole E E+ N H (-H+) instead of E N H N H Answer: The substitution product is favored since it comes from the arenium ion intermediate that is lower in energy/more stable (possesses three resonance forms vs only two for the substituted product), and hence will form faster 107 Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 194) Using a potential energy diagram, explain/illustrate the preferential formation of the substituted product instead of the product in the electrophilic aromatic substitution of thiophene E E+ instead of S (-H+) E S S Answer: The substitution product is favored since it comes from the arenium ion intermediate that is lower in energy/more stable (possesses three resonance forms vs only two for the substituted product), and hence will form faster 108 Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 195) Based on your knowledge of electrophilic aromatic substitution, and assuming the pyrrole ring of indole (shown) is activated toward electrophilic aromatic substituted more so than the benzenoid ring, predict the preferential position of attack of an electrophile, i.e., does the electrophile E+ attack carbon 2, or 3? Explain your answer E E+ (-H+) N H or E N H N H indole Which substitution product forms preferentially and why? Answer: 3-substitution is preferred, since this leads to a carbocation intermediate that can be resonance stabilized through the nitrogen, without loss of the benzenoid ring aromaticity This resonance form is lower in energy than those forming from the 2-substituted product, which although can be resonance stabilized through the benzenoid aromatic ring, produces resonance forms without aromaticity H H E E N H E E + N H N H 109 -H+ N H E+ E E N H N H E N H N H H H E E N H H N H H H -H+ E N H Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 196) Based on your knowledge of electrophilic aromatic substitution, and assuming the furan ring of benzo[b]furan (shown) is activated toward electrophilic aromatic substituted more so than the benzenoid ring, predict the preferential position of attack of an electrophile, i.e., does the electrophile E+ attack carbon 2, or 3? Explain your answer E E+ E + (-H ) O or O O benzo[b]furan Which substitution product forms preferentially and why? Answer: 3-substitution is preferred, since this leads to a carbocation intermediate that can be resonance stabilized through the oxygen, without loss of the benzenoid ring aromaticity This resonance form is lower in energy than those forming from the 2-substituted product, which although can be resonance stabilized through the benzenoid aromatic ring, produces resonance forms without aromaticity H H E E+ O E E O O 110 + -H O E+ E E O O O H H E E E O O O H H H -H+ O E Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 197) Based on your knowledge of electrophilic aromatic substitution, and assuming the thiophene ring of benzo[b]thiophene (shown) is activated toward electrophilic aromatic substituted more so than the benzenoid ring, predict the preferential position of attack of an electrophile, i.e., does the electrophile E+ attack carbon 2, or 3? Explain your answer E E+ E + (-H ) S or S S benzo[b]thiophene Which substitution product forms preferentially and why? Answer: 3-substitution is preferred, since this leads to a carbocation intermediate that can be resonance stabilized through the oxygen, without loss of the benzenoid ring aromaticity This resonance form is lower in energy than those forming from the 2-substituted product, which although can be resonance stabilized through the benzenoid aromatic ring, produces resonance forms without aromaticity H H E E S E E + S S 111 -H+ S E+ E E S S S H H E E E S S S H H H -H+ S E Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 198) Using a potential energy diagram, explain/illustrate the preferential formation of the substituted product instead of the product in the electrophilic aromatic substitution of benzo[b] thiophene (shown) E S E+ E instead of (-H+) S S benzo[b]thiophene Answer: 3-substitution is preferred, since this leads to a carbocation intermediate that can be resonance stabilized through the oxygen, without loss of the benzenoid ring aromaticity This resonance form is lower in energy than those forming from the 2-substituted product, which although can be resonance stabilized through the benzenoid aromatic ring, produces resonance forms without aromaticity 112 ‡ ‡ E S H Ea H Ea P.E E S Reaction Progress Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 199) Using a potential energy diagram, explain/illustrate the preferential formation of the substituted product instead of the product in the electrophilic aromatic substitution of benzo[b] furane (shown) E O E+ E instead of + (-H ) O O benzo[b]furan Answer: 3-substitution is preferred, since this leads to a carbocation intermediate that can be resonance stabilized through the oxygen, without loss of the benzenoid ring aromaticity This resonance form is lower in energy than those forming from the 2-substituted product, which although can be resonance stabilized through the benzenoid aromatic ring, produces resonance forms without aromaticity 113 ‡ ‡ E O H Ea H Ea P.E E O Reaction Progress Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 200) Using a potential energy diagram, explain/illustrate the preferential formation of the substituted product instead of the product in the electrophilic aromatic substitution of indole (shown) E N H E+ E instead of + (-H ) N H N H indole Answer: 3-substitution is preferred, since this leads to a carbocation intermediate that can be resonance stabilized through the nitrogen, without loss of the benzenoid ring aromaticity This resonance form is lower in energy than those forming from the 2-substituted product, which although can be resonance stabilized through the benzenoid aromatic ring, produces resonance forms without aromaticity 114 ‡ ‡ E N H Ea H H P.E Ea E N H Reaction Progress Topic: General EAS Reactivity, Mechanisms, Energy Diagrams Section: 15.2 and 15.11 Difficulty Level: Hard 201) Acid-catalyzed hydration of 1-phenyl-1-pentene gives 1-phenyl-1-pentanol almost exclusively; the other possible hydration product, 1-phenyl-2-pentanol, is not detected at all Explain clearly Answer: Acid catalyzed hydration of an alkene occurs through a carbocation intermediate Although 1-phenyl-1-pentene is symmetrically substituted at the C=C, the relative stabilities of the two possible carbocation intermediates is significantly different: although both are secondary carbocations, one is also benzylic and thus stabilized by resonance The observation that 1phenyl-1-pentene gives 1-phenyl-1-pentanol, almost exclusively, is in accordance with the general trend that acid catalyzed hydration chiefly tends to afford products formed via the most stable intermediate carbocation 115 H 2O H + H O+ + H + 2o, benzylic: stabilized by resonance,formed 2o, but not benzylic: less stable, not formed to any almost exclusively appreciable degree OH H + H chief product OH not detected Topic: Mechanism, Carbocation Stability Section: 15.12 Difficulty Level: Hard 202) When toluene reacts with Cl2, the identity of the major product(s) obtained depends on whether the reaction is carried out in the presence of catalytic amounts of FeCl3, or without catalyst, at high temp Explain clearly Answer: Reaction with Cl2/FeCl3 results in electrophilic aromatic substitution at the o- and ppositions, since the methyl group in toluene is an activating, o-,p- director In contrast, when the reaction is carried out without catalyst, at high temperature, the methyl group undergoes freeradical halogenation via the benzyl radical intermediate Cl2 FeCl3 Cl Cl + Cl Cl2 heat Topic: EAS/non-EAS Reactivity Section: 15.3 and 15.12 Difficulty Level: Medium 203) Suggest a reasonable synthetic strategy for the synthesis of 3,5-dinitrobenzyl alcohol from benzaldehyde 116 O NO2 HNO3 (excess) H2SO4 O2N heat O Answer: benzaldehyde NaBH4 H 2O NO2 OH O2N 3,5-dinitrobenzyl alcohol Topic: Synthetic Strategy Section: 15.14 Difficulty Level: Medium 204) Suggest a reasonable synthetic strategy for the synthesis of 4-methyl-1-phenyl-1-pentanol from 4-methylpentanoyl chloride, (CH3)2CHCH2CH2COCl O OH NaBH4 H 2O Cl O AlCl3 Answer: 4-methylpentanoyl chloride 4-methyl-1-phenyl-1-pentanol Topic: Synthetic Strategy Section: 15.7 Difficulty Level: Medium 205) Suggest a reasonable synthetic strategy for the synthesis of 6-methyl-3-phenyl-3-heptanol from 4-methylpentanoyl chloride, (CH3)2CHCH2CH2COCl O O OH i) C2H 5MgBr ii) NH 4Cl Cl AlCl3 Answer: 4-methylpentanoyl chloride 6-methyl-3-phenyl-3-heptanol Topic: Synthetic Strategy Section: 15.14 Difficulty Level: Hard 206) What product would result from the following series of reactions, 117 Br2, FeBr3 Mg, ether ethylene oxide H3O+ PBr3 Mg, ether O ? H3O+, heat (-H2O HF Answer: O Br2, FeBr3 OH MgBr Br Mg, ether H3O+ PBr3 O Br MgBr HF Mg, ether H 3O + (-H2O) Topic: Synthetic Strategy Section: 15.14 Difficulty Level: Hard 207) Propose a reasonable synthesis of the following compound from benzene multi-step process Answer: 118 O Br2, FeBr3 OH MgBr Br Mg, ether H3O+ PBr3 O Br MgBr HF Mg, ether H 3O + (-H2O) Topic: Synthetic Strategy Section: 15.14 Difficulty Level: Hard 208) What product would result from the following series of reactions: O AlCl3 SOCl2 O ? + AlCl3 O Answer: O O SOCl2 AlCl3 O + COOH O O O AlCl3 COCl O Topic: Synthetic Strategy Section: 15.14 Difficulty Level: Hard 119