Deck 9: Nucleophilic Substitution and Beta-Elimination

Question 1

Which of the following statements related to S_N1 reactions is not true?

A) The S_N1 reaction can be described as a heterolytic bond cleavage followed by nucleophilic attack
B) Carbocations are electrophilic
C) The charged carbon atom of a carbocation has an unfilled valence shell
D) Nucleophiles are Lewis acids

Answer 1

Nucleophiles are Lewis acids

Question 2

Which of the following alkyl halides undergoes the fastest S_N2 reaction with sodium cyanide, NaCN?

A) methyl iodide
B) ethyl iodide
C) 2-iodopropane
D) tert-butyl iodide

Answer 2

methyl iodide

Question 3

The reaction of tert-butyl chloride, (CH₃)₃CCl, with water in an inert solvent gives tert-butyl alcohol, (CH₃)₃COH. What is the effect of doubling the concentration of water on the rate of the reaction?

A) the rate remains the same
B) the rate decreases by a factor of 2
C) the rate increases by a factor of 2
D) the rate increases by a factor of 4

Answer 3

the rate remains the same

Question 4

Which of the following reactions corresponds to a substitution?

A) tert-butanol → tert-butyl chloride
B) tert-butanol → 2-methylpropene
C) 3,3-dimethyl-2-butanol → 2,3-dimethyl-2-butene
D) cyclohexene → 1,2-dichlorocyclohexane

Question 5

The reaction of 1-bromopropane with sodium iodide gives 1-iodopropane. What is the effect of doubling the concentration of NaI on the rate of the reaction?

A) the rate remains the same
B) the rate decreases by a factor of 2
C) the rate increases by a factor of 2
D) the rate increases by a factor of 4

Question 6

Which of the following alkyl halides undergoes the fastest S_N2 reaction with sodium azide, NaN₃?

A) 1-fluorohexane
B) 1-chlorohexane
C) 1-bromohexane
D) 1-iodohexane

Question 7

What is the equation for the rate of formation of tert-butyl alcohol from the reaction of tert-butyl bromide (t-BuBr) with water by an S_N1 mechanism?

A) Rate = k [t-BuBr]
B) Rate = k [t-BuBr][H₂O]
C) Rate = k [H₂O]
D) Rate = k [t-BuBr]²

Question 8

Which of the following statements related to S_N1 reactions is not true?

A) The heterolysis of a bond between atoms which do not bear formal charges always produces a cation and an anion
B) The charged carbon atom of a carbocation has a complete octet of valence shell electrons
C) Carbocations are Lewis acids
D) Nucleophiles seek centers of low electron density

Question 9

Which of the following is best set of conditions for the preparation of tert-butanol?

A) tert-butyl fluoride in water
B) tert-butyl bromide in water
C) tert-butyl fluoride and NaOH in DMSO
D) tert-butyl bromide and NaOH in DMSO

Question 10

The reaction of methyl iodide with sodium azide, NaN₃, proceeds by an S_N2 mechanism. What is the effect of doubling the concentration of NaN₃ on the rate of the reaction?

A) the rate remains the same
B) the rate decreases by a factor of 2
C) the rate increases by a factor of 2
D) the rate increases by a factor of 4

Question 11

Which of the following alkyl halides undergoes the fastest solvolysis reaction with ethanol, CH₃CH₂OH?

A) methyl fluoride
B) ethyl bromide
C) 2-chloropropane
D) tert-butyl bromide

Question 12

Which of the following alkyl halides undergoes the fastest S_N2 reaction with sodium methylthiolate, NaSMe?

A) methyl iodide
B) ethyl iodide
C) 2-bromopropane
D) tert-butyl chloride

Question 13

Which of the following alkyl halides undergoes the fastest solvolysis reaction with formic acid, HCOOH?

A) tert-butyl fluoride
B) tert-butyl chloride
C) tert-butyl bromide
D) tert-butyl iodide

Question 14

What is the equation for the rate of formation of 1-iodobutane from the reaction of 1-chlorobutane (BuCl) with NaI by an S_N2 mechanism?

A) Rate = k [BuCl]
B) Rate = k [BuCl][NaI]
C) Rate = k [NaI]
D) Rate = k [BuCl]²

Question 15

What is the equation for the rate of formation of 2-methoxypropane, CH₃CH(OCH₃)CH₃, from the reaction of 2-bromopropane (i-PrBr) with methanol?

A) Rate = k [i-PrBr]
B) Rate = k [i-PrBr]²
C) Rate = k [CH₃OH]
D) Rate = k [i-PrBr][CH₃OH]

Question 16

Which of the following alkyl halides undergoes the fastest solvolysis reaction with methanol, CH₃OH?

A) methyl chloride
B) ethyl chloride
C) 2-chloropropane
D) tert-butyl chloride

Question 17

Which of the following reactions corresponds to a substitution?

A) propene → 1,2-dibromopropane
B) 1-iodopropane → propene
C) propene → propane
D) 1-iodopropane → 1-bromopropane

Question 18

What is the equation for the rate of formation of 2-methoxypropane, (CH₃CH(OCH₃)CH₃, from the reaction of 2-bromopropane (i-PrBr) with sodium methoxide (NaOCH₃)?

A) Rate = k [i-PrBr]
B) Rate = k [i-PrBr]²
C) Rate = k [NaOCH₃]
D) Rate = k [i-PrBr][NaOCH₃]

Question 19

Which of the following is the best set of conditions for the preparation of tert-butyl methyl ether?

A) tert-butyl fluoride and NaOCH₃ in CH₃OH
B) methanol and sodium tert-butoxide in tert-butanol
C) fluoromethane and sodium tert-butoxide in tert-butanol
D) tert-butyl bromide and CH₃OH

Question 20

The reaction of tert-butyl bromide, (CH₃)₃CBr, with methanol in an inert solvent proceeds by an S_N1 mechanism to give tert-butyl methyl ether, (CH₃)₃COCH₃. What is the effect of doubling the concentration of methanol on the rate of the reaction?

A) the rate remains the same
B) the rate decreases by a factor of 2
C) the rate increases by a factor of 2
D) the rate increases by a factor of 4

Question 21

In which of the following solvents would the reaction of 1-bromobutane with sodium azide, NaN₃, proceed the fastest?

A) acetic acid
B) ethanol
C) water
D) acetonitrile

Question 22

What is(are) the major organic product(s) obtained from the following substitution reaction?

A) only 1
B) only 2
C) only 1 and 2
D) 1, 2 and 3

Question 23

Which of the following solvents is the best choice for the reaction of 1-chlorohexane with sodium bromide?

A) water
B) N,N-dimethylformamide
C) hexane
D) toluene, PhCH₃

Question 24

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 25

What is the major product formed upon treatment of (R) 1-bromo-4-methylhexane with sodium cyanide?

A) (R) 1-cyano-4-methylhexane
B) (S) 1-cyano-4-methylhexane
C) (R) 4-methyl-1-hexene
D) (S) 4-methyl-1-hexene

Question 26

Which of the following is the most nucleophilic?

A) sodium ethoxide
B) acetic acid
C) methanol
D) water

Question 27

Which of the following anions is the most nucleophilic in polar aprotic solvents?

A) F−
B) Cl−
C) Br−
D) I−

Question 28

What is the major organic product(s) obtained from the following reaction?

A) 3-methyl-1-pentyne
B) 3-methyl-2-pentyne
C) 1-propene + propyne
D) 4-methyl-2-pentene

Question 29

What is(are) the major organic product(s) obtained from the following substitution reaction?

A) only 1
B) only 2
C) only 1 and 2
D) 1, 2 and 3

Question 30

Which of the following solvents is the best choice for the reaction of 1-chlorohexane with sodium bromide?

A) dimethylsulfoxide
B) water
C) hexane
D) toluene, PhCH₃

Question 31

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 32

Which of the following compounds is the most nucleophilic in polar protic solvents?

A) H₂O
B) NH₃
C) H₂S
D) PH₃

Question 33

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 34

What is the major product formed upon treatment of (R) 2-bromohexane with sodium cyanide?

A) (R) 2-cyanohexane
B) (S) 2-cyanohexane
C) 1-hexene
D) 2-hexene

Question 35

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 36

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 37

What is the major organic product(s) obtained from the following reaction?

A) 1-hexyne
B) 2-hexyne
C) propene + propyne
D) propane + propyne

Question 38

What is(are) the major organic product(s) obtained from the following substitution reaction?

A) only 1
B) only 2
C) only 3
D) a mixture of 1 and 2

Question 39

Which of the following anions is the most nucleophilic in polar protic solvents?

A) F−
B) Cl−
C) Br−
D) I−

Question 40

What is(are) the major organic product(s) obtained from the following substitution reaction?

A) only 1
B) only 2
C) only 3
D) a mixture of 1 and 2

Question 41

Which of the following represents the transition state of the rate-determining step in the S_N1 reaction between tert-butyl chloride and water?

A) 1
B) 2
C) 3
D) 4

Question 42

Which of the following statements is not true regarding the S_N2 reaction of (R)-2-bromobutane with sodium cyanide?

A) the reaction proceeds with inversion of configuration
B) the rate is proportional to the concentration of sodium cyanide
C) the rate is proportional to the concentration of (R)-2-bromobutane
D) the rate of the reaction is independent of the identity of the solvent

Question 43

Which of the following energy diagrams represents the course of an exothermic E1 reaction?

A) 1
B) 2
C) 3
D) 4

Question 44

Which of the following compounds undergoes the most rapid hydrolysis reaction?

A) 1
B) 2
C) 3
D) 4

Question 45

Which of the following is not a characteristic of S_N2 reactions?

A) the electrophilic carbon undergoes inversion of stereochemistry
B) the rate is proportional to the concentration of substrate
C) the rate is proportional to the concentration of nucleophile
D) the rate is independent of the solvent

Question 46

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 47

Which of the following alkyl bromides reacts the slowest with NaSCH₃ in DMF?

A) 1
B) 2
C) 3
D) 4

Question 48

Which of the following statements is not true regarding S_N2 reactions?

A) A carbocation intermediate is formed.
B) The mechanism has only one step.
C) Aprotic solvents are good choices for S_N1 reactions.
D) The stereochemical outcome is inversion at the carbon bearing the leaving group.

Question 49

Which of the following is not a characteristic of S_N1 reactions?

A) the electrophilic carbon undergoes inversion of stereochemistry
B) the rate is proportional to the concentration of substrate
C) the reaction proceeds faster in a more polar solvent
D) the rate is independent of the concentration of nucleophile

Question 50

What is the role of tetrabutylammonium chloride as a phase transfer catalyst in the reaction of 1-chlorooctane and sodium cyanide in a mixture of water and CH₂Cl₂?

A) it transfers 1-chlorooctane into the aqueous phase
B) it transfers cyanide anion into the organic phase
C) it makes water and dichloromethane miscible
D) it transfers the sodium cation into the organic phase

Question 51

Which of the following statements is true regarding the reactivity of 1 and 2 with potassium tert-butoxide?

A) 1 reacts faster than 2
B) 1 and 2 give different dehydrochlorinated products
C) 2 reacts by elimination whereas 1 reacts by substitution
D) 1 reacts by elimination whereas 2 reacts by substitution

Question 52

Which of the following statements is not true regarding S_N1 reactions?

A) A carbocation intermediate is formed.
B) The mechanism has only one step.
C) Polar, protic solvents are good choices for S_N1 reactions.
D) The stereochemical outcome is racemization at the carbon bearing the leaving group.

Question 53

Which of the following energy diagrams represents the course of an exothermic S_N1 reaction?

A) 1
B) 2
C) 3
D) 4

Question 54

What is the major elimination product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 55

Which of the following statements is true regarding the reaction of tert-butyl bromide with water?

A) the rate is proportional to the concentration of tert-butyl bromide
B) the rate is proportional to the concentration of water
C) the rate is independent of the identity of the solvent
D) the rate of the reaction is independent of the temperature

Question 56

Which of the following is most likely to undergo rearrangement during reaction with methanol?

A) 1
B) 2
C) 3
D) 4

Question 57

Which of the following anions is the best leaving group in an S_N1 reaction?

A) F−
B) HO−
C) NH₂−
D) Cl−

Question 58

Which of the following is the best leaving group in an S_N2 reaction?

A) F−
B) H₃C−
C) CH₃O₂SO−
D) HO−

Question 59

Which of the following energy diagrams represents the course of an exothermic E2 reaction?

A) 1
B) 2
C) 3
D) 4

Question 60

Which of the following energy diagrams represents the course of an exothermic S_N2 reaction?

A) 1
B) 2
C) 3
D) 4

Question 61

The rate law for the following reaction would be of the form Rate = k[A][B].

Question 62

In the following reaction the cyanide ion is both a nucleophile and a Lewis acid.

Question 63

Which of the following sets consists of only polar protic solvents?

A) water, DMF, DMSO
B) acetic acid, methanol, water
C) DMSO, ethanol, acetonitrile
D) DMF, acetonitrile, DMSO

Question 64

The following reaction would be classified as an elimination.

Question 65

Which of the following represents the transition state of the rate-determining step in the reaction between 2-chloropropane and sodium amide leading to elimination?

A) 1
B) 2
C) 3
D) 4

Question 66

Which of the following represents the transition state of the reaction between methyl bromide and sodium methylthiolate, NaSCH₃?

A) 1
B) 2
C) 3
D) 4

Question 67

Which of the following represents the transition state of the rate-determining step in the reaction between tert-butyl iodide and water leading to elimination?

A) 1
B) 2
C) 3
D) 4

Question 68

What is the best choice of reagent to perform the following transformation?

A) H₂SO₄
B) H₂O
C) NaOCH₃
D) KOtBu

Question 69

Which of the following represents the transition state of the reaction between methyl iodide and ammonia?

A) 1
B) 2
C) 3
D) 4

Question 70

Which of the following represents the transition state of the rate-determining step in the reaction between tert-butyl bromide and methanol?

A) 1
B) 2
C) 3
D) 4

Question 71

The following reaction would have a faster rate in a higher polarity solvent than one of low polarity.

Question 72

What is the best choice of reagent to perform the following transformation?

A) H₂SO₄
B) H₂O
C) NaOCH₃
D) KOtBu

Question 73

The first step in the mechanism for the following reaction would be the formation of a secondary carbocation.

Question 74

HCl is the electrophile in the following reaction.

Question 75

The following energy diagram could represent an S_N2 reaction.

Question 76

Which of the following most favors elimination rather substitution in a reaction with sodium methoxide?

A) bromomethane
B) bromoethane
C) 1-bromopropane
D) 2-bromopropane

Question 77

Which of the following represents the transition state of the rate-determining step in the reaction between tert-butyl bromide and methanol leading to elimination?

A) 1
B) 2
C) 3
D) 4

Question 78

Which of the following represents the transition state of the rate-determining step in the reaction between 2-bromopropane and sodium methoxide leading to elimination?

A) 1
B) 2
C) 3
D) 4

Question 79

Which of the following most favors elimination rather substitution in a reaction with 2-bromopropane?

A) sodium methoxide
B) sodium ethoxide
C) sodium isoproxide
D) sodium tert-butoxide

Question 80

Which of the following sets consists of only polar aprotic solvents?

A) water, hexane, methanol
B) acetic acid, DMF, toluene
C) DMSO, ethanol, acetonitrile
D) DMF, acetonitrile, DMSO