Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) W hat is the nucleophile in the reaction show n below ?
A) I
B) II
C) III
1)
D) IV
E) V
D) CH3 NH2
E) PH3
Answ er: B
2) W hich of the follow ing is not a nucleophile?
A)
B)
2)
C) + CH3
Answ er: C
3) W hich of the follow ing best describes the carbon -chlorine bond of an alkyl chloride?
A) polar;
- at carbon and
3)
+ at chlorine
B) nonpolar; no dipole
C) ionic
D) polar;
+ at carbon and
- at chlorine
E) none of the above
Answ er: D
4) W hich of the follow ing is not normally considered to be a nucleophile?
A) CH3 CH2 +
B) NH2 CH3
C) NH3
4)
D)
Answ er: A
5) W hich of the follow ing are the substitution products of the reaction show n below ?
CH3 CH2 Br + - OH
?
A) CH3 CH2 BrH+ + OB) CH2
CHBr + H2 O
C) HOCH2 CH2 Br
D) CH3 CH2 OH + Br E) CH2
CH2 + Br - + H2 O
Answ er: D
1
5)
6) W hich of the follow ing alkyl halides gives the slow est SN2 reaction?
6)
A)
B)
C) CH3 CH2 Cl
D)
E)
Answ er: D
7) Assuming no other changes, w hat is the effect of doubling only the concentration of the alkyl
7)
halide in the above S N2 reaction?
A) rate is halved
B) quadruples the rate
C) no change
D) doubles the rate
E) triples the rate
Answ er: D
8) Assuming no other changes, w hat is the effect of doubling both the alkyl halide and the
nucleophile concentrations in the above reaction?
A) doubles the rate
B) rate is halved
C) quadruples the rate
D) triples the rate
E) no change
Answ er: C
2
8)
9) W hich of the follow ing S N2 reactions is the fastest?
A) CH3 CH2 CH3 Br + HO-
9)
CH3 CH2 CH3 OH + Br -
B)
C) CH3 CH2 CH2 I + H2 O
CH3 CH2 CH2 OH + HI
D) CH3 CH2 CH2 I + HO-
CH3 CH2 CH2 OH + I-
E)
Answ er: D
10) W hich of the follow ing S N2 reactions is the slow est?
A) CH3 CH2 CH2 Cl + HO-
10)
CH3 CH2 CH2 OH + Cl-
B) CH3 CH2 CH3 F + HO-
CH3 CH2 CH2 OH + F-
C) CH3 CH2 CH3 Br + HO-
CH3 CH2 CH3 OH + Br -
D)
E) CH3 CH2 CH2 I + HO-
CH3 CH2 CH2 OH + I-
Answ er: D
11) W hich of the follow ing compounds w ill undergo an S N2 reaction most readily?
11)
A) (CH3 )3 CCH2 I
B) (CH3 )2 CHCH2 CH2 CH2 I
C) (CH3 )2 CHI
D) (CH3 )2 CHCH2 CH2 CH2 Cl
E) (CH3 )3 CCl
Answ er: B
12) W hich of the follow ing is a secondary alkyl halide?
12)
A) (CH3 )3 CBr
B) (CH3 )2 CHBr
C) CH3 Br
D) (CH3 )2 CHCH2 Br
Answ er: B
13) W hich of the follow ing S N2 reactions is the fastest?
A) CH3 CH2 CHBrCH3 + OHB) CH3 CH2 CH2 CH2 Br + OHC) CH3 CH2 CHBrCH3 + H2 O
D) CH3 CH2 CH2 CH2 Br + H2 O
CH3 CH2 CHOHCH3 + Br CH3 CH2 CH2 CH2 OH + Br CH3 CH2 CHOHCH3 + HBr
CH3 CH2 CH2 CH2 OH + HBr
Answ er: B
3
13)
14) W hich of the follow ing S N2 reactions is the slow est?
A) CH3 CH2 CHBrCH3 + H2 O
B) CH3 CH2 CH2 CH2 Br + OHC) CH3 CH2 CHBrCH3 + OHD) CH3 CH2 CH2 CH2 Br + H2 O
14)
CH3 CH2 CHOHCH3 + HBr
CH3 CH2 CH2 CH2 OH + Br CH3 CH2 CHOHCH3 + Br CH3 CH2 CH2 CH2 OH + HBr
Answ er: A
15) W hich of the follow ing does not provide evidence that there are tw o different mechanisms for
15)
nucleophilic substitution?
A) the stereochemistry of nucleophilic substitutions
B) the effect of nucleophile concentration on rate
C) reaction products w hen (CH3 )3 CCH2 I is used as substrate
D) reaction products w hen CH3 I is used as the substrate
Answ er: D
16) W hat product results from the S N2 reaction betw een (R)-2-chloropentane and hydroxide?
A) 1-pentanol
B) 3-pentanol
C) (R)-2-pentanol
D) racemic pentanol
E) (S)-2-pentanol
Answ er: E
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
17) Provide a detailed, stepw ise mechanism for the reaction below .
(CH3 )2 CHCH2 CH2 CH2 I + CN-
17)
(CH3 )2 CHCH2 CH2 CH2 CN + I-
Answ er:
18) Do all primary alkyl iodides undergo S N2 reactions w ith sodium cyanide in DMSO at
18)
identical rates? Explain.
Answ er: No. All primary iodides are not equally accessible to attack by the CN - . Steric
hindrance varies among primary iodides.
19) Provide the structure of the maj or or ganic product w hich results w hen
(S)-2-iodopentane is treated w ith KCN in DMF.
Answ er:
4
19)
16)
20) Provide the structure of the maj or or ganic product in the follow ing reaction.
20)
Answ er:
21) Provide the structure of the maj or or ganic product in the follow ing reaction.
21)
(CH3 )3 N + CH3 CH2 CH2 I
Answ er: [(CH3 )3 NCH2 CH2 CH3 ] + I-
22) Provide the maj or or ganic product(s) in the reaction below .
22)
Answ er:
23) Provide the maj or or ganic product(s) in the reaction below .
Answ er:
5
23)
24) Provide the maj or or ganic product(s) in the reaction below .
24)
Answ er:
25) Draw and describe the transition state in the S N2 reaction betw een CH3 I and
25)
CH3 CH2 O- Na + .
Answ er: In this transition state the oxygen-carbon bond is partially for med and the
carbon-iodine bond is partially broken. There is essentially a trigonyl
bipyramidal electron geometry around the carbon being attacked by the
ethoxide, and the O-C-I angle is 180°. Both the oxygen and iodine atoms possess
a partial negative charge.
26) In an SN2 reaction w hy does the nucleophile attack the carbon on the side opposite the
26)
leaving group?
Answ er: Back side attack occurs because the or bital of the nucleophile that contains its
nonbonding electrons interacts w ith the empty
* MO associated w ith the
carbon-halogen bond. This or bital has its larger lob e on the side of the carbon
directed aw ay from the carbon-halogen bond, thus the nucleophile can achieve
the best overlap w ith this lob e.
27) Provide the structure of the maj or or ganic product of the follow ing reaction.
Answ er:
6
27)
28) Provide the structure of the maj or or ganic product of the follow ing reaction.
28)
Answ er:
29) Provide the structure of the maj or or ganic product of the follow ing reaction.
29)
Answ er:
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
30) W hich of the follow ing is the strongest nucleophile in an aqueous solution?
A) Cl-
B) Br -
C) I-
D) F-
30)
E) HO-
Answ er: C
31) W hich of the follow ing is the best leaving group?
A) HO-
B) I-
31)
C) Br -
D) F-
E) Cl-
Answ er: B
32) W hich of the follow ing species is most reactive in an SN2 reaction?
A) CH3 CH2
Cl
B) CH3 CH2
Br
C) CH3 CH2
F
D) CH3 CH2
OH
E) CH3 CH2
I
Answ er: E
7
32)
33) W hich of the follow ing species is the least nucleophilic?
33)
A) H2 O
B) (CH3 )3 N
C) BF3
D) CN-
E) (CH3 )3 COAnsw er: C
34) W hich of the follow ing is the best nucleophile in w ater?
A) I-
B) Cl-
C) CH3 OCH3
34)
D) CH3 SCH3
Answ er: A
35) W hich of the follow ing statements concerning SN2 reactions of alkyl halides is not correct?
35)
A) The rate of reaction depends on the concentration of the nucleophile.
B) The rate of r eaction depends on the concentration of the alkyl halide.
C) The rate of reaction depends on the relative nucleophilicity of the nucleophile.
D) The rate of r eaction of a particular alkyl bromide depends on the steric accessibility of the
carbon of the C-Br bond.
E) All alkyl iodides react more rapidly than all alkyl chlorides.
Answ er: E
36) W hich of the follow ing correctly describes the relative nucleophilicities of methoxide and
36)
tert-butoxide?
A) Methoxide is more nucleophilic because the nucleophilicity of tert-butoxide is diminished
by steric effects.
B) tert-Butoxide is more nucleophilic because it is more basic.
C) These alkoxides have essentially the same nucleophilicities since the negative charge in
both is localized on an oxygen atom.
D) tert-Butoxide is more nucleophilic because it contains three methyl groups w hich increase
the charge on its oxygen by donating electron density.
E) none of the above
Answ er: A
37) W hich of the follow ing bromides reacts readily via an S N2 reaction w ith NaN3 ?
37)
A) (CH3 )3 CCH2 CH2 CH2 Br
B) C6 H5 Br
C) 1-bromo-1-methylcyclohexane
D) CH3 CH2 CH=CHBr
E) (C6 H5 )3 CBr
Answ er: A
38) W hich halide reacts most rapidly via an S N2 mechanism?
A) (CH3 )CCH2 CH2 F
B) (CH3 )CCH2 CH2 Cl
C) (CH3 )CCH2 CH2 Br
D) (CH3 )CCH2 CH2 I
E) All primary halides react at the same rate in S N2.
Answ er: D
8
38)
39) W hich halide reacts most rapidly via an S N2 mechanism?
A)
B)
C)
D)
E)
Answ er: E
9
39)
40) W hich halide reacts most rapidly via an S N2 mechanism?
40)
A)
B)
C)
D)
E)
Answ er: E
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
41) Rank the species below in order of increasing nucleophilicity in protic solvents:
41)
CH3 CO2 - , CH3 S- , HO- , H2 O.
Answ er: H2 O < CH3 CO2 - < HO- < CH3 S42) In each of the pairs below , w hich is the best nucleophile in alcoholic solvents?
a.
CH3 S- or CH3 O-
b.
(CH3 )2 NH or (CH3 )3 N
c.
Cl- or F-
d.
SCN- or OCN-
Answ er: a.
CH3 S-
b.
(CH3 )2 NH
c.
Cl-
d.
SCN-
10
42)
43) W hy, in a polar protic solvent, is iodide a better nucleophile than fluor ide?
43)
Answ er: In addition to iodide being mor e polarizable due to its larger size, the fluor ide ion
is more highly solvated w hich retards its ability to funct ion as a nucleophile.
44) A student attempted to prepare 1-chlor ob utane by treating 1-butanol w ith NaCl in
44)
acetone. W as the student successful? Explain.
Answ er: The student w as unsuccessful. The reaction w ould require chlor ide to displace
hydroxide. Since hydroxide is a much stronger base, and therefor e a much
poorer leaving group, the reaction does not occur.
45) Rank the species below in or der of leaving group capabilities in S N2 reactions (w orst
45)
leaving group to b est):
CH3 O- , H2 O, C6 H5 SO3 - , H2 N- .
Answ er: H2 N- < CH3 O- < C6 H5 SO3 - < H2 O
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
46) Assuming no other changes, w hat is the effect of doubling only the concentration of the alkyl
46)
halide in the above S N1 reaction?
A) triples the rate
B) no change
C) rate is halved
D) doubles the rate
E) quadruples the rate
Answ er: D
47) Assuming no other changes, w hat is the effect of doubling only the concentration of the
47)
nucleophile in the above reaction?
A) quadruples the rate
B) no change
C) rate is halve
D) doubles the rate
E) triples the rate
Answ er: B
48) Assuming no other changes, w hat is the effect of doubling both the concentration of the alkyl
halide and the nucleophile in the above reaction?
A) quadruples the rate
B) doubles the rate
C) rate is halved
D) no change
E) triples the rate
Answ er: B
11
48)
49) W hich of the follow ing alkyl halides gives the fastest S N1 reaction?
49)
A)
B) CH3 CH2 CH2 Cl
C)
D) CH3 CH2 CH2 Br
E) CH3 CH2 CH2 I
Answ er: A
50) W hich of the follow ing alkyl halides gives the fastest SN1 reaction?
50)
A)
B)
C)
D)
E)
Answ er: E
51) W hich of the follow ing factors has no effect on the rate of S N1 reactions?
A) the nature of the alkyl halide
B) the nature of the leaving group
C) the concentration of the nucleophile
D) the value of the rate constant
E) the concentration of the alkyl halide
Answ er: C
12
51)
52) W hich of the follow ing car bocations is the most stable?
52)
A)
B)
C)
D)
E)
Answ er: A
53) W hich of the follow ing is the rate law for S N1 mechanisms?
53)
A) Rate = k[Nucleophile]
B) Rate = k[Alkyl Halide] [Nucleophile]
C) Rate = k[Alkyl Halide]
D) Rate = k[Alkyl Halide] [Nucleophile] + k2 [Alkyl Halide]
E) Rate = k1 [Alkyl Halide] + k2 [Nucleophile]
Answ er: C
54) W hich of the follow ing car bocations is the least stable?
A) I
B) II
C) III
54)
D) IV
Answ er: A
13
E) V
55) W hich of the compounds below undergoes solvolysis in aqueous ethanol most rapidly?
55)
A) methyl iodide
B) cyclohexyl bromide
C) 3-iodo-3-methylpentane
D) 3-chloropentane
E) isopropyl chloride
Answ er: C
56) In the SN1 hydrolysis mechanism of (CH3 )3 CBr, there are __________ elementary steps,
56)
__________ distinct transition stat es, and __________ distinct intermediates.
A) 2, 2, 2
B) 2, 3, 2
C) 2, 2, 3
D) 3, 3, 2
E) 3, 2, 3
Answ er: D
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
57) Provide the maj or or ganic product of the reaction below and a detailed, stepw ise
mechanism w hich accounts for its formation.
Answ er:
14
57)
58) Provide the structure of the maj or or ganic products w hich result in the reaction below .
58)
Answ er:
59) Provide the structure of the maj or or ganic product of the follow ing reaction.
59)
Answ er:
60) Provide the maj or or ganic product(s) in the reaction below .
60)
Answ er:
61) Provide the maj or or ganic product(s) in the reaction below .
Answ er:
15
61)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
62) W hich of the follow ing car bocations does not rear range?
62)
A)
B) CH3 CH2 CHCH3
C)
D)
E) all the above
Answ er: E
63) W hich of the follow ing alkyl bromides undergoes solvolysis in methanol w ithout
63)
rearrangement?
A) (R)-3-bromo-2-methylpentane
B) (S)-3-bromo-2-methylpentane
C) 3-bromo-3-ethylpentane
D) (R)-2-bromo-3-ethylpentane
E) (S)-2-bromo-3-ethylpentane
Answ er: C
64) W hich of the follow ing alkyl bromides is likely to undergo r earrangement by a 1, 2 -methyl
64)
shift?
A) 3-bromo-2, 3-dimethylpentane
B) benzyl bromide
C) 3-bromo-3-methylpentane
D) 2-bromo-3, 3-dimethylpentane
E) 2-bromo-3-ethylpentane
Answ er: D
65) A 1,2-methyl shift occurs w hen w hich of the follow ing iodides is heated in ethanol?
A) (CH3 )2 CHCHICH3
B) C6 H5 CHICH(CH3 )2
C) (CH3 )3 CCH2 CH2 I
D) (CH3 )2 C=CHI
E) (CH3 )3 CCHICH2 CH3
Answ er: E
16
65)
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
66) Provide the maj or or ganic product(s) in the reaction below .
66)
Answ er:
67) Provide the structure of the maj or or ganic product w hich results in the follow ing
67)
reaction.
Answ er:
68) List the follow ing compounds in or der of increasing reactivity in an S N1 reaction.
68)
CH3 Br, CH3 CH2 CH2 I, (CH3 )3 CI, CH3 CHBrCH3 , CH3 CHICH3
Answ er: CH3 Br < CH3 CH2 CH2 I < CH3 CHBrCH3 < CH3 CHICH3 < (CH3 )3 CI
69) List the follow ing compounds in or der of increasing reactivity in an S N1 reaction.
CH3 Br, CH3 CH2 CH2 I, (CH3 )3 CI, CH3 CHBrCH3 , CH3 CHICH3
Answ er: CH3 Br < CH3 CH2 CH2 I < CH3 CHBrCH3 < CH3 CHICH3 < (CH3 )3 CI
17
69)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
70) W hen (S)-2-bromob utane undergoes an S N2 reaction w ith CH3 O- , the product is the
70)
compound show n below . W hat is/are the configuration(s) of the product(s) obtained from this
reaction?
A) S only
B) R only
C) equal mixture of R and S
D) a mixture of enantiomers w ith mor e R than S
E) a mixture of enantiomers w ith mor e S than R
Answ er: B
71) The specific rotation of optically pure (R)-sec-butyl alcohol is -13.52°. An optically pure sample
71)
of (R)-sec-butyl bromide w as converted into the cor responding sec-butyl alcohol via an S N2
reaction. W hat is the specific rotation of the product, assuming 100% yield?
A) zero
B) betw een 0° and -13.52°
C) -13.52°
D) +13.52°
E) betw een 0° and +13.52°
Answ er: D
72) SN1 reactions usually proceed w ith:
72)
A) equal amounts of inversion and retention at the center undergoing substitution.
B) slightly more inversion than r etention at the center undergoing substitution.
C) slightly more retention than inversion at the center undergoing substitution.
D) complete retention at the center undergoing substitution.
E) complete inversion at the center undergoing substitution.
Answ er: B
73) The specific rotation of optically pure (R)-C6 H5 CHOHCH3 is -42.3°. An optically pure sample of
(R)-C6 H5 CHClCH3 w as converted into the cor responding alcohol via an S N2 reaction. W hat is
the specific rotation of the product?
A) +42.3°
B) betw een +42.3° and 0°
C) -42.3°
D) betw een 0° and -42.3°
Answ er: A
18
73)
74) W hen (S)-1-bromo-1 phenylethane undergoes an S N1 r eaction w ith methanethiol (CH3 SH),
the product is the compound show n. W hat is/are the configuration(s) of the product ob tained
from this reaction?
A) S only
B) R only
C) a mixture of the enantiomers, w ith slightly mor e S than R
D) a mixture of the enantiomers, w ith slightly mor e R than S
Answ er: D
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
75) Provide the structure of the maj or or ganic product of the follow ing reaction.
75)
Answ er:
76) Provide the structure of the maj or or ganic product(s) of the follow ing reaction.
Answ er:
19
76)
74)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
77) W hich of the follow ing can't undergo nucleophilic substitution reactions?
A) I
B) II
C) III
77)
D) IV
E) V
Answ er: B
78) W hich of the follow ing is classified as a vinyl halide?
A) CH3 CH
CHCl
B) CH3 CH
CHOH
78)
C) CH3 CH2 CH2 CH2 Br
D) CH3 CH
CHCH2 Cl
E) BrCH2 CH
CH2
Answ er: A
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
79) Explain w hy allyl chloride undergoes S N1 reactions even though it is a 1° halide?
CH2
79)
CHCH2 Cl
allyl chloride
Answ er: Allyl chloride forms a relatively stable allylic carbocation w ith tw o contributing
resonance structures.
80) W hy are vinylic halides unreactive in both S N2 and SN1 reactions?
80)
Answ er: Vinylic halides do not undergo S N2 reactions because as the nucleophile
approaches the back side of the sp2 carbon it is repelled by the
electron cloud of
the double bond. They do not undergo S N1 reactions because vinylic
carbocations are prohibitively unstable (less stable than primary carbocations).
20
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
81) W hich of the follow ing solvents is aprotic?
81)
A) CH3 CH2 NHCH3
B) CH3 CH2 CH2 NH2
C) CH3 CH2 OH
D) CH3 CH2 OCH2 CH3
E)
Answ er: D
82) W hich of the follow ing solvents is protic?
82)
A) CH3 CH2 CH2 Cl
B)
C) CH3 CH2 OH
D)
E) CH3 CH2 OCH3
Answ er: C
83) Protic and aprotic solvents are very similar as solvents except for their
83)
A) ability to stabilize cations w ith unshared pair s of electrons.
B) polarity.
C) ability to stabilize anions by hydrogen bonding.
D) dielectric constant.
E) ability to stabilize cations by hydrogen bonding.
Answ er: C
84) W hich of the follow ing best explains w hy S N1 reactions involving a neutral reactant are faster
in polar solvents?
A) The nucleophile is solvated by polar solvents.
B) The substrate is mor e soluble in polar solvents.
C) Solvation by polar solvents stabilizes the carbocation.
D) Solvation by polar solvents stabilizes the transition state.
E) The substrate is less soluble in polar solvents.
Answ er: D
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84)
85) W hich of the follow ing statements is generally true for S N1 reactions?
85)
A) The mechanism is a one-step back attack.
B) Reaction rates depend only on the concentration of the nucleophile.
C) These are favor ed by nonpolar solvents.
D) These reactions are favor ed by polar solvents.
E) Complete inversion of configur ation occurs.
Answ er: D
86) The hydr olysis of tert-butyl chlor ide proceeds mor e rapidly in a solvent mixture w hich is 70%
w ater/30% acetone than in one w hich is 30% w ater/70% acetone. W hy?
A) The solvent w hich contains a greater percentage of w ater is less polar, and this
destabilizes the tert-butyl chloride.
B) The transition state in the carbocation for mation step is better stabilized in the mor e
polar solvent mixture.
C) The reaction proceeds by an S N2 mechanism w herein the rate is increased by increasing
the concentration of the nucleophile w ater.
D) The reaction proceeds by an S N1 mechanism w herein the rate is increased by increasing
the concentration of the nucleophile w ater.
E) none of the above
Answ er: B
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
87)
87) Consider the follow ing reaction mechanism:
W hat effect w ill the follow ing have on the rate?
a.
addit ion of Br -
b.
using a mor e polar solvent
c.
using a stronger nucleophile
d.
using a more concentrated nucleophile
Answ er: a.
b.
reaction w ill slow dow n because of competition w ith Nu reaction w ill speed up because a mor e polar solvent assists in ionization and
the formation of the carbocation
c.
d.
no effect on SN1 reactions
no effect on SN1 reactions
88) Explain w hy SN2 reactions proceed faster in the solvent dimethylsulfoxide than in
ethanol?
CH3 SOCH3
CH3 CH2 OH
dimethlysolfoxide
ethanol
Answ er: Dimethlysulfoxide is an aprotic solvent. Ethanol is a protic solvent w hich can
hydrogen bond to the nucleophile, decreasing its nucleophilicity. Therefor e, S N2
reactions favor aprotic solvents.
22
88)
86)
89) W hat type of solvent is best for S N2 reactions w hich employ anionic nucleophiles:
89)
polar, protic solvents; polar, aprotic solvents; or nonpolar solvents? Explain.
Answ er: Polar, aprotic solvents are best. These solvents have strong dipole moments to
enhance solubility of the anionic species but lack the ability to solvate the anion
by hydrogen bonding.
90) W hen nucleophile and leaving group are contained in the same molecule, is
90)
intermolecular or intramolecular reaction favored? Explain.
Answ er: The answ er depends on the concentration of the bifunctional molecule and the
size of the ring that w ill be for med in the intramolecular reaction. The
intramolecular reaction has the advantage of reacting groups being tethered
close together and therefore not having to w ander through the solvent to find
each other. As a result, a low concentration of r eactant favor s intramolecular
reaction over intermolecular. Additionally, if the intramolecular reaction w ould
form a five- or six-membered ring, it w ould be highly favor ed since smaller ring
formations are retarded by angle strain and larger ring formations are retarded
by less favorable entropy considerations.
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
91) W hich of the follow ing correctly describes SAM, a biological methylating agent?
91)
A) It contains a Cl bonded to a 1° carbon.
B) It contains a methyl group bonded to a positively charged sulfur atom.
C) It contains a methyl ether.
D) it contains a methyl group bonded to an aromatic ring.
E) It contains a Br bonded to a phosphor us atom.
Answ er: B
92) W hat is the leaving group in the reaction show n below ?
A) I
B) II
C) III
92)
D) IV
Answ er: A
23
E) V