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Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) W hich of the follow ing are the elimination products of the reaction show n below ?
CH3 CH2 Br + - OH
1)
?
A) CH2
CH2 + Br - + H2 O
B) CH2
CHBr + H2 O
C) CH3 CH2 Br + H + OD) CH3 CH2 OH + Br E) HOCH2 CH2 Br
Answ er: A
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
2) Draw the alkene product w hich results w hen 1-bromopentane is heated in acetone
2)
containing NaOH. Give a detailed, step-by-step mechanism for the production of this
compound.
Answ er:
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
3) W hich of the follow ing compounds undergoes E2 r eactions w ith the fastest rate?
A) CH3 CH2 CH2 I
B)
C) CH3 CH2 CH2 Br
D) CH3 CH2 CH2 Cl
E)
Answ er: B
1
3)
4) W hich of the follow ing bases gives the highest anti-Zaitsev product in E2 reactions w hen
reacted w ith 2-bromo-2, 3-dimethylbutane?
A)
B)
C)
D)
E)
Answ er: B
2
4)
5) W hat is the maj or product of the follow ing E2 reaction?
5)
A)
B) CH3 CH2 CH
CH2
C)
D)
E)
Answ er: E
6) How many distinct alkene products are possible w hen the alkyl iodide below undergoes E2
6)
elimination?
A) 1
B) 2
C) 3
D) 4
E) 5
Answ er: E
7) W hich of the alkyl chlor ides listed below undergoes dehydrohalogenation in the presence of a
strong base to give 2-pentene as the only alkene product?
A) 2-chloropentane
B) 3-chloropentane
C) 1-chloro-2-methylbutane
D) 1-chloro-3-methylbutane
E) 1-chloropentane
Answ er: B
3
7)
8) W hen 2-bromo-3-methyl-1-phenylbutane is treated w ith sodium methoxide, w hy is the
8)
maj or product 3-methyl-1-phenyl-1-butene?
A) SN2 predominates over E2.
B) The less substituted alkene is alw ays mor e stable than the mor e substituted alkene.
C) The new ly for med double bond in this compound is conj ugated w ith the phenyl ring.
D) E1 predominates over E2.
E) The bulkiness of the methoxide results in the less substituted alkene.
Answ er: C
9) W hat is the maj or or ganic product of the follow ing reaction?
9)
A) (E)-2,3-dimethyl-3-hexene
B) 2,3-dimethyl-2-hexene
C) (Z)-2,3-dimethyl-3-hexene
D) 2,3-dimethyl-1-hexene
E) 2-isopropyl-1-pentene
Answ er: B
10) W hat is the maj or or ganic product of the follow ing reaction?
10)
A) (Z)-2,3-dimethyl-3-hexene
B) 2,3-dimethyl-1-hexene
C) (E)-2,3-dimethyl-3-hexene
D) 2,3-dimethyl-2-hexene
E) 2-isopropyl-1-pentene
Answ er: E
11) W hich of the follow ing halides is most reactive in an E2 reaction w ith sodium methoxide?
A) (CH3 )2 CHCH2 Br
B) (CH3 )3 CCH2 I
C) (CH3 )2 CHCH2 CH2 Cl
D) (CH3 )2 CHCHICH3
E) (CH3 )2 CHCH2 Cl
Answ er: D
4
11)
12) W hich of the follow ing halides is least reactive in an E2 reaction w ith sodium methoxide?
12)
A) (CH3 )2 CHCH2 Cl
B) (CH3 )3 CCH2 I
C) (CH3 )2 CHCH2 CH2 Cl
D) (CH3 )2 CHCHICH3
E) (CH3 )2 CHCH2 Br
Answ er: B
13) W hich of the follow ing statements is true concerning the E2 reactions of alkyl fluor ides?
13)
A) Alkyl fluor ides react to form the most stable carbocation intermediate.
B) The transition state of this E2 reaction resembles a carbanion rather than an alkene.
C) Alkyl fluor ides cannot adopt the proper stereochemical alignment for an E2 reaction to
occur.
D) Alkyl fluorides react more readily in E2 reactions than do alkyl iodides.
E) The C-F bond is the w eakest carbon-halogen bond so S N2 w ill alw ays predominate over
E2 in the reactions of alkyl fluorides.
Answ er: B
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
14) W hen 1-iodo-1-methylcyclohexane is treated w ith NaOCH2 CH3 , the mor e highly
14)
substituted alkene product predominates. W hen KOC(CH3 )3 is used instead, the less
highly substituted alkene product predominates. Offer an explanation.
Answ er: The unhindered ethoxide produces the mor e stable alkene product (ie, the mor e
highly substituted alkene possible). When the bulky t-butoxide is used, the most
accessible hydrogen is removed. This results in the least highly substituted
alkene possible.
15) Provide the structure of the maj or or ganic product w hich results w hen
2-bromo-2-methylbutane is treated w ith sodium ethoxide.
Answ er:
5
15)
16) Draw all likely alkene products in the follow ing reaction and circle the product you
16)
expect to predominate.
Answ er:
17) Draw all likely alkene products in the follow ing reaction and circle the product you
expect to predominate.
Answ er:
6
17)
18) Draw all likely alkene products in the follow ing reaction and circle the product you
18)
expect to predominate.
Answ er:
19) Supply the missing alkyl halide reactant in the elimination reactions show n below .
Answ er: a)
bromomethylcyclohexane
b)
CH3 CH2 CHBrCH2 CH3
c)
CH3 CH2 CH(CH3 )CH2 Br
7
19)
20) Provide the structure of the maj or or ganic product of the follow ing reaction.
20)
Answ er:
21) Provide the structure of the maj or or ganic product of the follow ing reaction.
Answ er:
8
21)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
22) W hich of the follow ing alkyl halides undergoes E1 reactions w ith the fastest rate?
22)
A)
B) CH3 I
C)
D)
E)
Answ er: E
23) W hich of the follow ing alkyl halides for ms the most stable carbocation w hen it undergoes an E1
reaction?
A) I
B) II
C) III
D) IV
Answ er: D
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E) V
23)
24) W hich of the follow ing statements cor rectly describe(s) E1 reactions of alkyl halides (RX)?
I.
Rate = k[base]
II.
Rate = k[base][RX]
III.
Rate = k[RX]
24)
IV. The reactions occur in tw o distinct steps.
V.
Rearrangements are sometimes seen.
A) III and V
B) I only
C) III, IV, and V
D) II and IV
E) I, IV, and V
Answ er: C
25) Consider the follow ing experimental data for the rate of the reaction given below :
Experiment #1
[Alkyl Halide]
[Base]
Rate
1
0.01
0.01
1
2
0.02
0.01
2
3
0.01
0.02
1
25)
W hat is the mechanism for the reaction?
A) first or der, SN1
B) first or der, SN2
C) first or der, E2
D) first or der, E1
E) none of the above
Answ er: D
26) W hich of the follow ing correctly reflects relative stabilities of carbocations?
A) 3° benzylic > vinyl > 1°
B) 1° benzylic > 3° > 3° allylic
C) methyl > 2° benzylic > 3°
D) 2° allylic > 2° > vinyl
E) 3° allylic > 2° > 1° benzylic
Answ er: D
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26)
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
27) W hen 1-bromo-2, 2-dimethylcyclopentane is heated in ethanol, one of the products
27)
w hich results is show n below . Provide a detailed, stepw ise mechanism for the
production of this compound, and give the name of the mechanism by w hich it is
pr oduced.
Answ er:
28) List the follow ing compounds in order of increasing reactivity in an E1 elimination.
28)
CH3 CH2 CHBrCH3 , CH3 CH2 CH2 CH2 Br, (CH3 )3 CBr
Answ er: CH3 (CH2 )3 Br < CH3 CH2 CHBrCH3 < (CH3 )3 CBr
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
29) Dehydr ohalogenation of 2-bromob utane in the presence of a strong base proceeds via w hich of
the follow ing mechanistic pathw ays?
A) SN2
B) SN1
C) E1
D) E2
E) none of the above
Answ er: D
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29)
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
30) Provide the structure of the maj or or ganic product in the follow ing reaction.
30)
Answ er:
31) W hy is the E1 not a likely mechanism w hen 1-chloropentane is heated in ethanol?
31)
Answ er: Primary halides cannot undergo E1 reactions because of the difficulty
encountered in forming primar y car bocations.
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
32) W hich of the follow ing is least likely to b e found in the product mixture w hich results w hen
32)
2-iodopentane reacts w ith sodium ethoxide in ethanol?
A) (E)-2-pentene
B) 1-pentene
C) 2-ethoxypentane
D) 1-ethoxypentane
E) (Z)-2-pentene
Answ er: D
33) W hat is the maj or product w hich results w hen (2R,3S)-2-chloro-3-phenylbutane is treated
w ith sodium methoxide in methanol?
A) (E)-2-phenyl-2-butene
B) (S)-3-phenyl-1-butene
C) (Z)-2-phenyl-2-butene
D) (R)-2-methoxy-2-phenylbutane
E) (R)-3-phenyl-1-butene
Answ er: C
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33)
34) W hy is the alkyl halide below not capable of undergoing an E2 reaction upon treatment w ith
34)
sodium ethoxide?
A) Br - is too poor a leaving group.
B) Sodium ethoxide is a poor base to use in E2 reactions.
C) The substrate is too hindered.
D) The C-H and C-Br bonds w hich need to break cannot achieve an anti-periplanar
orientation.
E) Too much angle strain w ould be present in the alkene product.
Answ er: D
35) W hich of the compounds show n below is/are the product(s) of this reaction:
A) I only
B) II only
C) I is minor , II is maj or .
D) I and II are of equal yield.
E) I is maj or , II is minor .
Answ er: A
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35)
36) W hich of the follow ing compounds is/are the products of this reaction:
36)
A) I only
B) II only
C) I and II are of equal yield.
D) I is minor , II is maj or .
E) I is maj or , II is minor .
Answ er: D
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
37) Provide the structure of the maj or or ganic product w hich results in the follow ing
reaction.
Answ er:
14
37)
38) Provide the structure of the maj or or ganic product w hich results in the follow ing
38)
reaction.
Answ er:
39) W hich diastereomer of 1-bromo-4-t-butylcyclohexane, the cis or the trans, undergoes
39)
elimination more rapidly w hen treated w ith sodium ethoxide? Explain your answ er.
Answ er: The cis isomer reacts mor e quickly. An axial or ientation of the C-Br bond is
required for E2 in six-membered ring systems. In or der for this to occur in the
trans isomer, the bulky t-butyl group must also assume an axial or ientation;
this requires substantial energy of activation.
40) Provide the structure of the maj or or ganic product w hich results in the follow ing
reaction.
Answ er:
15
40)
41) Provide the structure of the maj or elimination product w hich results w hen the alkyl
41)
bromide below is heated in ethanol.
Answ er:
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
42) A primary kinetic isotope effect could most likely be ob served in w hich of the follow ing
42)
mechanisms?
A) SN2
B) SN1 and SN2
C) E1 and SN1
D) E2
E) E1
Answ er: D
43) W hat is the maj or product of the follow ing reaction?
A)
B) CH3 CH
CHCH3
C)
D) CH3 CH2 CH2 CH2 OCH2 CH3
E) CH2
CHCH2 CH3
Answ er: B
16
43)
44) W hat is the maj or product of the follow ing reaction?
44)
A)
B) CH2
CHCH2 CH3
C) CH3 CH2 CH2 CH2 OCH2 CH3
D)
E) CH3 CH
CHCH3
Answ er: D
45) W hat is the maj or product of the follow ing reaction?
A) I
B) II
C) III
45)
D) IV
Answ er: E
17
E) V
46) W hat is/are the product(s) of the follow ing reaction?
46)
A)
B) CH2
CH2
C)
D) A and B
E) A and C
Answ er: A
47) Predict the tw o most likely mechanisms for the reaction of 2 -iodohexane w ith sodium ethoxide.
47)
A) E1 and E2
B) SN2 and E2
C) E2 and SN1
D) SN2 and SN1
E) E1 and SN1
Answ er: B
48) Predict the tw o most likely mechanisms w hich occur w hen 2 -iodohexane is heated in ethanol.
A) E1 and SN1
B) SN2 and SN1
C) E1 and E2
D) SN2 and E2
E) E2 and SN1
Answ er: A
18
48)
49) W hat is/are the product(s) of the follow ing reaction?
A) CH2
49)
CH2
B)
C)
D) A and B
E) A and C
Answ er: D
50) W hat mechanism predominates in the reaction below ?
A) SN1 w ith rearrangement
B) SN2
C) SN1 w ithout rearrangement
D) E1
E) E2
Answ er: B
19
50)
51) W hat mechanism predominates in the reaction below ?
51)
A) SN2
B) SN1 w ithout rearrangement
C) E2
D) E1
E) SN1 w ith rearrangement
Answ er: E
52) W hat mechanism predominates in the reaction below ?
52)
A) E1
B) SN2
C) SN1 w ith rearrangement
D) SN1 w ithout rearrangement
E) E2
Answ er: E
53) W hich of the follow ing is least likely to b e found in the product mixture w hich results w hen the
alkyl iodide below is heated in w ater?
A) I
B) II
C) III
D) IV
Answ er: D
20
E) V
53)
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
54) W hich base, ammonia (NH3 ) or triethylamine [(CH3 CH2 )3 N], w ould be a better choice
54)
for use in converting 1-chlorohexane to 1-hexene? Explain briefly.
Answ er: Triethylamine. Amines can serve as both nucleophiles and as bases in reactions
w ith alkyl halides. Increasing the steric bulk about the nitrogen diminishes the
nucleophilicity w hile allow ing the amine to continue to funct ion effectively as a
base.
55) Provide the structure of the maj or or ganic product of the follow ing reaction.
55)
Answ er:
56) Can primary alkyl halides react by S N2, SN1, E2, and E1 mechanisms? Ar e any of these
56)
mechanisms prohibited? W hat conditions favor a particular mechanism?
Answ er: Only SN2 and E2 pathw ays are available to primary halides. S N1 and E1 cannot
occur due to the instability of primary carbocations. S N2 w ill typically
predominate over E2 unless there is steric hindrance in the alkyl halide or
nucleophile/base.
57) W hat reaction mechanism predominates w hen 1-bromo-1-propylcyclopentane is
57)
treated w ith sodium methoxide in methanol?
Answ er: E2
58) W hat reaction mechanism predominates w hen 1-bromo-1-propylcyclopentane is
58)
heated in ethanol?
Answ er: SN1
59) Provide the maj or or ganic product(s) in the reaction below .
Answ er:
21
59)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
60) Starting w ith 2-butene, w hich of the follow ing is the best method for preparing 2 -butyne?
A) Br 2 /CCl4 ; Zn/H+ ; H2 /Ni
B) HBr; H2 /Ni; Zn/H+
C) Br 2 /CCl4 ; 2NaNH2
D) HBr; NaNH2
E) HBr; Zn/H+ ; H2 /Ni
Answ er: C
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
61) W hich of the follow ing alkyl chlorides w ould undergo substitution most rapidly w hen
61)
treated w ith NaCCH: chlor oethane, 2-chloropropane, or 1-chloro-2,
2-dimethylpropane? Provide the structure of the substitution product.
Answ er: Chloroethane reacts most rapidly; CH3 CH2 C
CH is pr oduced.
62) Show the best w ay to prepare CH3 OCH(CH3 )2 by an SN2 reaction.
62)
Answ er: CH3 I + NaOCH(CH3 )2
63) W rite the structures for the products of the follow ing S N2 reactions.
Answ er: a)
3-cyclopentyl-1-propyne
b)
2-iodo-4-methylpentane
c)
1-methoxypropane
22
63)
60)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
64) W hat is the maj or product of the follow ing reaction?
A) CH2
64)
CHCH2 CH2 CH2 OH
B)
C)
D) CH2
CHCH
CHCH3
E) CH2
CHCH2 CH
CH2
Answ er: D
65) W hich sequence of r eagents w or ks best to convert 3-hexene to 3-hexyne?
65)
A) 1. Br 2 , CH2 Cl2 2. NaNH2 (excess)
B) 1. HCl 2. NaNH2
C) 1. BH3 ·THF 2. HO- , H2 O2 3. NaNH2
D) 1. NaNH2 2. HI 3. H3 O+
E) 1. Cl2 , CH2 Cl2 2. NaCN (excess)
Answ er: A
66) W hich sequence of r eagents w or ks best to convert 1-bromob utane to hexane?
66)
A) 1. NaC CCH2 CH3 2. Na, NH3
B) 1. NaC CH 2. H2 (excess), Pd/C
C) 1. NaOCH3 , CH3 OH 2. NaCN 3. Na, NH3
D) 1. NaCN 3. BH3 *THF 4. HO- , H2 O2
E) 1. CH3 CH2 OH, delta 2. H2 (excess), Pd/C
Answ er: B
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
67) Provide the maj or or ganic product(s) in the reaction below .
Answ er:
23
67)
68) Provide the maj or or ganic product(s) in the reaction below .
Answ er:
24
68)