CHEM 2323 Handout #7 - Substitution Reactions.doc

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Unformatted text preview: CHEM 2323 Organic Chemistry I Handout #7 – Substitution Reactions (SN1 & SN2) 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 2) Provide an acceptable name for the compound shown below. 3) 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 4) What is the IUPAC 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 5) 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 6) 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 7) Which of the following species is the least nucleophilic? A) H2O B) BF3 C) (CH3)3N D) CH3OE) CN- 8) Provide a detailed, stepwise mechanism for the reaction below. (CH3)2CHCH2CH2CH2I + CN- → (CH3)2CHCH2CH2CH2CH2CN + I9) What type of solvent is best for SN2 reactions which employ anionic nucleophiles: polar, protic solvents; polar, aprotic solvents; or nonpolar solvents? Explain. 10) Provide the structure of the major organic product which results when (S)-2-iodopentane is treated with KCN in DMF. 11) 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. 12) 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 13) Provide the structure of the major organic product in the following reaction. 14) Predict the two most likely mechanisms for the reaction of 2-iodohexane with sodium ethoxide. A) SN2 and SN1 B) E1 and E2 C) SN2 and E2 D) E1 and SN1 E) E2 and SN1 15) 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 16) Which of the following compounds is the most nucleophilic? A) CH3SH B) CH3OH C) H2O D) CH3CO2H E) BF3 17) 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. 18) List the following bromides in order of their increasing reactivity as substrates in S N2 reactions: 2-chlorobutane, 2iodobutane, and 1-iodobutane. 19) Which halide is a better nucleophile, iodide or fluoride? Explain. 20-26) Provide the structure of the major organic product for the reactions shown below: 27) Provide the major organic product of the reaction below and a detailed, stepwise mechanism which accounts for its formation. 28) When ionization occurs at the single stereocenter of a chiral compound, the resulting carbocation is: A) achiral B) chiral C) racemic D) optically active E) none of the above 29) 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. 30) Predict the two most likely mechanisms which occur when 2-iodohexane is heated in ethanol. A) SN2 and SN1 B) E1 and E2 C) SN2 and E2 D) E1 and SN1 E) E2 and SN1 31) Which of the following alkyl halides is most likely to undergo rearrangement in an S N1 reaction? A) 3-bromopentane B) 2-chloro-3,3-dimethylpentane C) 3-chloropentane D) bromocyclohexane E) 1-bromo-4-methylcyclohexane 32) Which of the following solvents could be described as polar and protic? A) ethanol B) acetonitrile C) dimethylformamide D) acetone E) 18-crown-6 33) Rank the following molecules in order of increasing relative rate of S N1 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 34) 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 35) 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 36-40) Provide the structure of the major organic product for the reactions 31-35 shown below: 41) Arrange the following compounds in order of increasing reactivity toward ethanol solvolysis: t-butyl bromide, t-butyl iodide, isopropyl chloride, methyl iodide. 42) List the following bromides in order of their increasing reactivity as substrates in S N1 reactions: 1-iodo-1-ethylcyclopentane, chlorocyclopentane, and iodocyclopentane. 43) List the following bromides in order of their increasing reactivity as substrates in S N1 reactions: PhBr, PhCH2Br, and PhCH(CH3)Br. 44) 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 ...
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  • Fall '16
  • Dr. Karlos Moreno
  • Nucleophilic substitution, Alkyl, IUPAC nomenclature of organic chemistry, propyl

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