Deck 10: Elimination Reactions of Alkyl Halides Competition Between Substitution and Elimination

Question 1

Give the major product for the following E2 reaction.

A)
B)
C)
D)
E)

Answer 1

Question 2

Which of the alkyl chlorides listed below undergoes dehydrohalogenation in the presence of a strong base to give 2-pentene as the only alkene product?

A)1-chloropentane
B)2-chloropentane
C)3-chloropentane
D)1-chloro-2-methylbutane
E)1-chloro-3-methylbutane

Answer 2

3-chloropentane

Question 3

How many distinct alkene products are possible when the alkyl iodide below undergoes E2 elimination?

A)1
B)2
C)3
D)4
E)5

Answer 3

5

Question 4

Which of the following bases gives the highest anti-Zaitsev product in E2 reactions when reacted with 2-bromo-2, 3-dimethylbutane?

A)
B)
C)
D)
E)

Question 5

Draw the alkene product which results when 1-bromopentane is heated in acetone containing NaOH. Give a detailed, step-by-step mechanism for the production of this compound.

Question 6

When 2-bromo-3-methyl-1-phenylbutane is treated with sodium methoxide, why is the major product 3-methyl-1-phenyl-1-butene?

A)S_N2 predominates over E2.
B)E1 predominates over E2.
C)The bulkiness of the methoxide results in the less substituted alkene.
D)The newly formed double bond in this compound is conjugated with the phenyl ring.
E)The less substituted alkene is always more stable than the more substituted alkene.

Question 7

Which of the following halides is most reactive in an E2 reaction with sodium methoxide?

A)(CH₃)₃CCH₂I
B)(CH₃)₂CHCHICH₃
C)(CH₃)₂CHCH₂Br
D)(CH₃)₂CHCH₂Cl
E)(CH₃)₂CHCH₂CH₂Cl

Question 8

Which of the following compounds undergoes E2 reactions with the fastest rate?

A)
B)CH₃CH₂CH₂Cl
C)CH₃CH₂CH₂I
D)
E)CH₃CH₂CH₂Br

Question 9

What is the major organic product of the following reaction?

A)2,3-dimethyl-1-hexene
B)2,3-dimethyl-2-hexene
C)2-isopropyl-1-pentene
D)(Z)-2,3-dimethyl-3-hexene
E)(E)-2,3-dimethyl-3-hexene

Question 10

What is the most reactive alkyl halide for elimination reactions?

A)1-chlorobutane
B)1-fluorobutane
C)1-iodobutane
D)1-bromobutane

Question 11

Give the major product for the following E2 reaction.

A)
B)
C)
D)
E)none of the above

Question 12

What is the major organic product of the following reaction?

A)2,3-dimethyl-1-hexene
B)2,3-dimethyl-2-hexene
C)2-isopropyl-1-pentene
D)(Z)-2,3-dimethyl-3-hexene
E)(E)-2,3-dimethyl-3-hexene

Question 13

Which of the following halides is least reactive in an E2 reaction with sodium methoxide?

A)(CH₃)₃CCH₂I
B)(CH₃)₂CHCHICH₃
C)(CH₃)₂CHCH₂Br
D)(CH₃)₂CHCH₂Cl
E)(CH₃)₂CHCH₂CH₂Cl

Question 14

Which of the following are the elimination products of the reaction shown below? CH₃CH₂Br + ^-OH → ?

A)CH₃CH₂Br⁺H + O^-
B)HOCH₂CH₂Br
C)CH₃CH₂OH + Br^-
D)CH₂ CH₂ + Br^- + H₂O
E)CH₂ CHBr + H₂O

Question 15

Give the mechanism of the reaction shown below.

Question 16

Which alkyl halide reacts the fastest in an E2 reaction?

A)2-chloro-2-methylbutane
B)1-chlorobutane
C)1-chloro-2-methylbutane
D)2-chlorobutane
E)chloromethane

Question 17

Give the mechanism of the reaction shown below.

Question 18

What is the major product of the following E2 reaction?

A)
B)CH₃CH₂CH CH₂
C)
D)
E)

Question 19

Give the major product for the E2 reaction.

A)
B)
C)
D)
E)

Question 20

Which of the following statements is true concerning the E2 reactions of alkyl fluorides?

A)Alkyl fluorides react more readily in E2 reactions than do alkyl iodides.
B)The transition state of this E2 reaction resembles a carbanion rather than an alkene.
C)The C-F bond is the weakest carbon-halogen bond so S_N2 will always predominate over E2 in the reactions of alkyl fluorides.
D)Alkyl fluorides react to form the most stable carbocation intermediate.
E)Alkyl fluorides cannot adopt the proper stereochemical alignment for an E2 reaction to occur.

Question 21

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.

Question 22

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 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

Question 23

Which of the following alkyl halides undergoes E1 reactions with the fastest rate?

A)
B)
C)
D)
E)CH₃I

Question 24

Provide the major organic product of the following reaction.

Question 25

Provide the major organic product of the following reaction.

Question 26

Which of the following correctly reflects relative stabilities of carbocations?

A)3° allylic > 2° > 1° benzylic
B)methyl > 2° benzylic > 3°
C)3° benzylic > vinyl > 1°
D)2° allylic > 2° > vinyl
E)1° benzylic > 3° > 3° allylic

Question 27

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.

Question 28

Provide the major organic product of the following reaction.

Question 29

Consider the following experimental data for the rate of the reaction given below: What is the mechanism for the reaction?

A)first order, S_N1
B)first order, S_N2
C)first order, E1
D)first order, E2
E)none of the above

Question 30

Provide the major organic product of the following reaction.

Question 31

Which of the following alkyl halides forms the most stable carbocation when it undergoes an E1 reaction?

A)I
B)II
C)III
D)IV
E)V

Question 32

Provide the structure of the major organic product which results when 2-bromo-2-methylbutane is treated with sodium ethoxide.

Question 33

Supply the missing alkyl halide reactant in the elimination reactions shown below.

Question 34

Draw all likely alkene products in the following reaction and circle the product you expect to predominate.

Question 35

List the following compounds in order of increasing reactivity in an E1 elimination.
CH₃CH₂CHBrCH₃, CH₃CH₂CH₂CH₂Br, (CH₃)₃CBr

Question 36

Provide the structure of the major organic product of the following reaction.

Question 37

Draw all likely alkene products in the following reaction and circle the product you expect to predominate.

Question 38

Provide the structure of the major organic product of the following reaction.

Question 39

Draw all likely alkene products in the following reaction and circle the product you expect to predominate.

Question 40

Provide the major organic product of the following reaction.

Question 41

Which of the compounds shown below is/are the product(s)of this reaction?

A)I only
B)II only
C)I and II are of equal yield.
D)I is major, II is minor.
E)I is minor, II is major.

Question 42

Give the major product for the following E1 reaction.

A)
B)
C)
D)
E)

Question 43

Dehydrohalogenation of 2-bromobutane in the presence of a strong base proceeds via which of the following mechanistic pathways?

A)S_N1
B)S_N2
C)E1
D)E2
E)none of the above

Question 44

Provide the structure of the major organic product in the following reaction.

Question 45

Give the major product for the following E2 reaction.

A)
B)
C)
D)
E)no reaction

Question 46

Why is the E1 not a likely mechanism when 1-chloropentane is heated in ethanol?

Question 47

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.

Question 48

Which of the following is least likely to be found in the product mixture which results when 2-iodopentane reacts with sodium ethoxide in ethanol?

A)1-ethoxypentane
B)2-ethoxypentane
C)(Z)-2-pentene
D)(E)-2-pentene
E)1-pentene

Question 49

Why is the alkyl halide below not capable of undergoing an E2 reaction upon treatment with sodium ethoxide?

A)Br^- is too poor a leaving group.
B)The substrate is too hindered.
C)Too much angle strain would be present in the alkene product.
D)Sodium ethoxide is a poor base to use in E2 reactions.
E)The C-H and C-Br bonds which need to break cannot achieve an anti-periplanar orientation.

Question 50

Provide the structure of the major organic product which results in the following reaction.

Question 51

What is the major product which results when (2R,3S)-2-chloro-3-phenylbutane is treated with sodium methoxide in methanol?

A)(E)-2-phenyl-2-butene
B)(Z)-2-phenyl-2-butene
C)(S)-3-phenyl-1-butene
D)(R)-3-phenyl-1-butene
E)(R)-2-methoxy-2-phenylbutane

Question 52

Identify the alkyl halide that reacts the fastest in a E1 reaction.

A)
B)
C)
D)
E)

Question 53

A primary kinetic isotope effect could most likely be observed in which of the following mechanisms?

A)S_N1 and S_N2
B)S_N2
C)E1 and S_N1
D)E2
E)E1

Question 54

Give the major product for the following E1 reaction.

A)
B)
C)
D)
E)no reaction

Question 55

Give the mechanism of the reaction shown below.

Question 56

Give the mechanism of the reaction shown below.

Question 57

Provide the structure of the major elimination product which results when the alkyl bromide below is heated in ethanol.

Question 58

Provide the structure of the major organic product which results in the following reaction.

Question 59

Which of the following compounds is/are the products of the following reaction?

A)I only
B)II only
C)I and II are of equal yield.
D)I is major, II is minor.
E)I is minor, II is major.

Question 60

Provide the structure of the major organic product which results in the following reaction.

Question 61

Give the major product for the following reaction.

A)
B)
C)
D)
E)

Question 62

Provide the structure of the major organic product of the following reaction.

Question 63

What is the major product of the following reaction?

A)CH₂ CHCH₂CH₃
B)CH₃CH CHCH₃
C)
D)CH₃CH₂CH₂CH₂OCH₂CH₃
E)

Question 64

What mechanism predominates in the reaction below?

A)S_N2
B)S_N1 without rearrangement
C)S_N1 with rearrangement
D)E2
E)E1

Question 65

What mechanism predominates in the reaction below?

A)S_N2
B)S_N1 without rearrangement
C)S_N1 with rearrangement
D)E2
E)E1

Question 66

What is/are the product(s)of the following reaction?

A)
B)CH₂ CH₂
C)
D)A and B
E)A and C

Question 67

What is/are the product(s)of the following reaction?

A)
B)CH₂ CH₂
C)
D)A and B
E)A and C

Question 68

Provide the major organic product(s)in the reaction below.

Question 69

Can primary alkyl halides react by S_N2, S_N1, E2, and E1 mechanisms? Are any of these mechanisms prohibited? What conditions favor a particular mechanism?

Question 70

Predict the two most likely mechanisms which occur when 2-iodohexane is heated in ethanol.

A)S_N2 and S_N1
B)E1 and E2
C)S_N2 and E2
D)E1 and S_N1
E)E2 and S_N1

Question 71

Which of the following is least likely to be found in the product mixture which results when the alkyl iodide below is heated in water?

A)I
B)II
C)III
D)IV
E)V

Question 72

What reaction mechanism predominates when 1-bromo-1-propylcyclopentane is treated with sodium methoxide in methanol?

Question 73

Give the best answer for the reaction.

A)
B)
C)
D)
E)

Question 74

What is the major product of the following reaction?

A)I
B)II
C)III
D)IV
E)V

Question 75

What reaction mechanism predominates when 1-bromo-1-propylcyclopentane is heated in ethanol?

Question 76

Which base, ammonia (NH₃)or triethylamine [(CH₃CH₂)₃N], would be a better choice for use in converting 1-chlorohexane to 1-hexene? Explain briefly.

Question 77

What is the major product of the following reaction?

A)CH₂ CHCH₂CH₃
B)CH₃CH CHCH₃
C)
D)CH₃CH₂CH₂CH₂OCH₂CH₃
E)

Question 78

Give the major product(s)for the following reaction.

A)
B)
C)
D)
E)

Question 79

What mechanism predominates in the reaction below?

A)S_N2
B)S_N1 without rearrangement
C)S_N1 with rearrangement
D)E2
E)E1

Question 80

Predict the two most likely mechanisms for the reaction of 2-iodohexane with sodium ethoxide.

A)S_N2 and S_N1
B)E1 and E2
C)S_N2 and E2
D)E1 and S_N1
E)E2 and S_N1