Deck 6: Alkyl Halides; Nucleophilic Substitution

Question 1

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 1

3,3-dichloropentane

Question 2

Which of the following best describes the carbon-chlorine bond of an alkyl chloride?

A) nonpolar; no dipole
B) polar; δ+ at carbon and δ- at chlorine
C) polar; δ- at carbon and δ+ at chlorine
D) ionic
E) none of the above

Answer 2

polar; δ+ at carbon and δ- at chlorine

Question 3

Provide an acceptable name for CH₃CH₂CH₂C(CH₃)₂I.

Answer 3

2-iodo-2-methylpentane

Question 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

Question 5

Provide the structure of isopropyl iodide.

Question 6

Which of the following is classified as a vinylic halide?

A) CH₃CH CHOH
B) CH₃CH CHCl
C) CH₃CH CHCH₂Cl
D) CH₃CH₂CH₂CH₂Br
E) BrCH₂CH CH₂

Question 7

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

Question 8

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

Question 9

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

Question 10

Provide the structure of 1-bromo-3-methylhexane.

Question 11

Provide an acceptable name for CHCl₃.

Question 12

Draw the structure of cis-1,3-dichlorocyclopentane.

Question 13

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

Question 14

Provide an acceptable name for the compound shown below.

Question 15

Provide the name of the bromoalkane shown below.

Question 16

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

Question 17

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

Question 18

Provide an acceptable name for the compound shown below.

Question 19

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

Question 20

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

Question 21

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

Question 22

Provide a detailed, stepwise mechanism for the reaction below.
(CH₃)₂CHCH₂CH₂CH₂I + CN^- → (CH₃)₂CHCH₂CH₂CH₂CH₂CN + I^-

Question 23

Provide the major organic product of the reaction below.

Question 24

Name the haloalkane shown. Be sure to include the appropriate R or S description if needed.

Question 25

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.

Question 26

Although F is more electronegative than Cl, the C-Cl bond has a larger dipole moment than the
Explain.

Question 27

When water is shaken with dichloromethane, a two-phase system results. Which compound forms the upper phase? Explain.

Question 28

Which of the following alkyl halides has the smallest molecular dipole moment?

A) CH₃F
B) CH₃Cl
C) CH₂I₂
D) CH₂Cl₂
E) CF₄

Question 29

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

Question 30

What type of intermediate is present in the S_N2 reaction of cyanide with bromoethane?

A) carbocation
B) free radical
C) carbene
D) carbanion
E) This reaction has no intermediate.

Question 31

Name the haloalkane shown. Be sure to include the appropriate R or S description if needed.

Question 32

The term CFC is an abbreviation for ________.

Question 33

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

Question 34

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

Question 35

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

Question 36

Show how the following reaction might be constructed using an S_N2 reaction by drawing structures for the starting materials.

Question 37

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

Question 38

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.

Question 39

Draw two reasonable resonance structures and the hybrid of the intermediate formed in the following reaction.

Question 40

Arrange the following alkyl halides in order of increasing boiling point:
CH₃CH₂Br, CH₃CH₂CH₂Br, (CH₃)₂CHBr, CH₃CH₂F.

Question 41

Which of the following compounds will undergo an S_N2 reaction most readily?

A) (CH₃)₃CCH₂I
B) (CH₃)₃CCl
C) (CH₃)₂CHI
D) (CH₃)₂CHCH₂CH₂CH₂I
E) (CH₃)₂CHCH₂CH₂CH₂Cl

Question 42

Which halide is a better nucleophile, iodide or fluoride? Explain.

Question 43

Arrange the following substrates in order of their increasing S_N2 reactivity with NaCN:
bromoethane, 1-chloro-3,3-dimethylpentane, 1-chloro-2,2-dimethylpentane, and 2-bromo-2-methylpentane.

Question 44

List the following bromides in order of their increasing reactivity as substrates in S_N2 reactions: PhBr, PhCH₂Br, and PhCH(CH₃)Br.

Question 45

Do all primary iodides react with N₃^- at the same rate via the S_N2 mechanism? Explain.

Question 46

Rank the species below in order of increasing nucleophilicity in hydroxylic solvents:
CH₃CO₂^-, CH₃S^-, HO^-, H₂O.

Question 47

Arrange the following species in order of increasing nucleophilicity:
CH₃CH₂S^-, CH₃CH₂O^-, (CH₃)₃CO^-, (CH₃)₃COH.

Question 48

Which of the following solvents could be described as polar and protic?

A) ethanol
B) acetonitrile
C) dimethylformamide
D) acetone
E) 18-crown-6

Question 49

List the following alkyl halides in order of their increasing reactivity as substrates in S_N2 reactions: 2-chlorobutane, 2-iodobutane, and 1-iodobutane.

Question 50

Which of the following alkyl chlorides would undergo substitution most rapidly when treated with

or
Provide the structure of the substitution product.

Question 51

Provide the structure of the major organic product in the following reaction.
(CH₃)₃N + CH₃CH₂CH₂I →

Question 52

Which of the following alkyl chlorides will undergo S_N2 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

Question 53

Which of the following compounds is the most nucleophilic?

A) CH₃SH
B) CH₃OH
C) H₂O
D) CH₃CO₂H
E) BF₃

Question 54

Consider the substitution reaction shown below. By what mechanism will the reaction proceed?

A) S_N1
B) S_N2
C) free radical reaction
D) There is not enough information to tell.

Question 55

What type of solvent is best for S_N2 reactions which employ anionic nucleophiles: polar, protic solvents; polar, aprotic solvents; or nonpolar solvents? Explain.

Question 56

Which of the following factors is favorable for nucleophilicity but not basicity?

A) highly polarizable
B) low electronegativity
C) negatively charged
D) sterically hindered

Question 57

Name one factor that is favorable for nucleophilicity but not for basicity.

Question 58

Which is more nucleophilic, t-butoxide or ethoxide? Explain.

Question 59

Do all primary alkyl iodides undergo S_N2 reactions with sodium cyanide in DMSO at identical rates? Explain.

Question 60

Which of the following species is the least nucleophilic?

A) H₂O
B) BF₃
C) (CH₃)₃N
D) CH₃O^-
E) CN^-

Question 61

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

Question 62

Provide the structure of the major organic product which results when (S)-2-iodopentane is treated with KCN in DMF.

Question 63

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

Question 64

List the following bromides in order of their increasing reactivity as substrates in S_N1 reactions: 1-iodo-1-ethylcyclopentane, chlorocyclopentane, and iodocyclopentane.

Question 65

List the following compounds in order of increasing reactivity in an S_N1 reaction.
CH₃Br, CH₃CH₂CH₂I, (CH₃)₃CI, CH₃CHBrCH₃, CH₃CHICH₃

Question 66

Draw the highest energy transition state in the solvolysis of (CH₃)₃CI in CH₃OH.

Question 67

S_N2 reactions take place with ________ of stereochemistry at the center undergoing substitution.

Question 68

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

Question 69

List the following bromides in order of their increasing reactivity as substrates in S_N1 reactions: PhBr, PhCH₂Br, and PhCH(CH₃)Br.

Question 70

Provide the major organic product of the reaction below.

Question 71

Provide the major organic product of the reaction below.

Question 72

Which of the following alkyl halides reacts most rapidly via an S_N1 solvolysis reaction in hot methanol?

A) 1-iodohexane
B) 1-fluorohexane
C) (R)-2-bromohexane
D) iodocyclohexane
E) 1-iodo-1-methylcyclohexane

Question 73

Show the best way to prepare CH₃OCH(CH₃)₂ by an S_N2 reaction.

Question 74

Provide the major organic product of the S_N2 reaction below.

Question 75

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.

Question 76

Complete the following S_N2 reaction by providing structures for the necessary starting materials.

Question 77

List the following bromides in order of their increasing reactivity as substrates in S_N1 reactions: 2-chlorobutane, 2-iodobutane, and 1-iodobutane.

Question 78

Which of the following alkyl halides reacts most rapidly via an S_N2 reaction with NaCN?

A) 1-iodohexane
B) 1-fluorohexane
C) (R)-2-bromohexane
D) iodocyclohexane
E) 1-iodo-1-methylcyclohexane

Question 79

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

Question 80

Arrange the following compounds in order of increasing reactivity toward ethanol solvolysis:
t-butyl bromide, t-butyl iodide, isopropyl chloride, methyl iodide.