11.1 What is wrong with the use of such names as “isopropanol” and “tert-butanol”?
Answer: We should say them as “isopropyl alcohol” and “tert-butyl alcohol”.
11.2 Give bond-line formulas and appropriate names for all of the alcohols and ethers with the
formulas (a) C3H8OH and (b) C4H10O
(a)
OH
CH3CH2 CH2 OH
H3C
propanol
C
H
CH3 OCH2CH3
CH3
2-propanol
Ethyl methyl ether
(b)
H3C
OH
CH3CH2CH2 CH2 OH
butanol
H2
C
H3C
C
H
H3C
CH3
C
OH
H3C
2-butanol
tert-butyl alcohol
CH3
CH3 OCH2CH2CH3
propyl methyl ether
CH3CH2OCH2 CH3
diethyl ether
H3C
C
H
OCH3
isopropyl methy ether
OH
2-methyl-1-propanol
11.3 1,2-Propanediol and 1,3-propanediol(propylene glycol and trimethylene glycol, respectively;
see Table11.2)have higher boiling points than any of the butyl alcohols, even though all of the
compounds have roughly the same molecular weight. How can you explain this observation.
The diols have two –OH, so it can form stronger hydrogen bonding. Therefore, 1,2-Propanediol
and 1,3-propanediol have higher boiling points than any of the butyl alcohols.
11.4 What products would you expect from acid-catalyzed hydration of each of the following
alkene?
(a) Ethene
(c)2-Methylpropene
(b)Propene
(d)2-Methyl-1-butene
H3O
(a)
OH
OH
H3O
(b)
OH
H 3O
(c)
H 3O
HO
(d)
11.5 Treating 3,3-dimethyl-1-butene with dilute sulfuric acid is largely unsuccessful as a method
for preparing 3,3-dimethyl-2-butanol because an isomeric compound is the major product. What is
this isomeric compound and how is it formed?
H
3 ,3 -d im eth y l-1 -b u ten e
OH
2 ,3 -D im e th y l-b u ta n -2 -o l (m ain )
11.6 Starting with an appropriate alkene, show all steps in the synthesis of each of the following
alcohols by oxymercuration-demercuration.
(a) tert-Butyl alcohol (b) Isopropyl alcohol (c) 2-Methyl-2-butanol
Answer:
(a)
(1) H g(O A c) 2 /T H F-H 2 O
OH
(2) N aB H 4 ,O H
tert-butyl alcohol
(b)
(1) Hg(O Ac) 2 /THF-H 2 O
HO
(2) NaBH 4 ,OH
Isopropyl alcohol
(c)
(1) Hg(OAc)2/THF-H2O
(2) NaBH4 ,OH
HO
2-Methyl2-butanol
11.7 When an alkene is treated with mercuric trifluoroacetate, Hg (O2CCF3)2, in THF containing
an alcohol, ROH, the product is an (alkoxyalkyl) mercury compound. Treating this product with
NaBH4/OH- results in the formation of an ether. The overall process is called
solvomercuration-demercuration.
RO
Hg(O2CCF3 )2/THF-ROH
solvomercuraton
NaBH4 ,OHdemercuraton
HgO2CCF3
Alkene
(Alkoxyalkyl)mercuric trifluoroacetate
H
OR
Ether
a) Outline a likely mechanism for the solvomercuration step of this ether synthesis. b) Show how
you would use solvomercuration-demercuration to prepare tert-butyl methyl ether.
a) Step 1:
O
F
Hg
O
O
O
F
F
F
F
O
F
Hg
O
+
F
F
F
O
F
O
F
F
Step 2:
O
δ
F
Hg
O
O
F
F
δ
F
Hg
O
F
F
Step 3:
OH
OH
R
R
R
OH
δ
O
O
δ
Hg
F
F
Hg
O
F
O
F
F
F
OH
O
F
Hg
O
F
Step 4(demercuration):
F
H
OH
OH
NaBH4, OHO
F
Hg
O
F
F
b) The reaction is:
HgO2CCF3
Hg(O2 CCF3)2 /THF-CH3 OH O
O
NaBH4,OHdemercuraton
solvomercuraton
11.8 Starting with an appropriate alkene, show the synthesis for (a) tributylborane, (b)
triisobutylborane, and (c) tri-sec-butylborane. (d) Show the stereochemistry involved in the
hydroboration of 1-methylcyclohexene.
a) tributylborane
B
THF:BH3
b) triisobutylborane
THF:BH3
B
c) tri-sec-butylborane
THF:BH3
d) Hydroboration of 1-methylcyclohexene
B
H
H
B
B
11.9 Treating a hindered alkene such as 2-methyl-2butene with THF: BH3 lead to the formation of
a dialkborane instead of a trialkylborane. When 2 mol of 2-methyl-2butene adds to 1mol of BH3,
the product formed has the nickname“disiamylborane.” Write its structure. Disamylborane is a
useful reagent in certain syntheses that require a sterically hindered borane. ( The name “disiamyl”
comes from“di-secondary－iso-amyl,” a completely unsystematic and unacceptable name. The
name “amyl” is an old common name for a five-carbon alkyl group.)
The answer:
H
H
B
H
H
11.10 Starting with the appropriate alkene show how you could use hydroboration –oxidation to
prepare each of the following alcohols.
(a) 1-Pentanol
(b) 2-Methyl-1-pentanol
(c) 3-Methyl-2pentanol
(d) 2-Methyl-3-pentanol
(e) trans-2methylcyclobutanol
(a)
(b)
THF:BH3
THF:BH3
(CH3CH2CH2CH2CH2)3B
(CH3CH2CH2CHCH3CH2)3B
H2O2
OH
NaOH
H2O2
NaOH
OH
OH
(c)
THF:BH3
H2O2
(CH3CH2CHCH3CHCH3)3B
NaOH
H2O2
THF:BH3
(d)
NaOH
OH
3
B
(e)
CH3
H
H
CH3
CH3
THF:BH3
H
H2O2
H
CH3
OH
H
+
+
NaOH
BH2
H
BH2
H
H
OH
11.11 Starting with any needed alkene (or cycloalkene), and assuming you have deuterioacetic
acid (CH3CO2D) available, outline syntheses of the following deuterium labeled compounds.
(a) (CH3)2CHCH2CH2D
Answer:
O
H
D
O
THF:BH3
3
D
△
B
H
(b) (CH3)2CHCHDCH3
Answer:
O
D
O
THF: BH3
△
D
BH2
CH3
(c)
D
(+ enantiomer)
Answer:
O
CH3
CH3
THF: BH3
CH3
D
O
△
BH2
D
(d) Assuming you also have available THF: BD3 and CH3CO2T, can you suggest a synthesis of
the following?
D
T
CH3
(+ enantiomer)
H
Answer:
D
O
D
T
CH3
THF: BD3
O
BH2CH3
T
CH3
△
H
H
H
11.12 Write equations for the acid-base reactions that would occur (if any) if ethanol were added
to solutions to each of the following compounds. In each reaction, label the stronger acid, the
stronger base, and so forth.
(a) sodium amide, (b) sodium ethynide, and (c) sodium acetate (consult Table 3.1)
Answer:
+
Na+ -C
+
Na+
Na+
NH2-
OH
OH
+
O
NH2-
O
Na+
O
+
-C
Na+
+
Na+
+
NH3
NH3
O
+
O
+
Na+
OH
Na+
O-
OH
So the relative basicity of these bases: sodium amide > sodium ethynide > sodium acetate
11.13 Suggest an experiment using an isotopically labeled alcohol that would prove that the
formation of an alkyl sulfonate does not cause cleavage at the C－O bond of the alcohol.
Solution:
We can use alcohol CH3CH218OH to react with methanesulfonyl chloride. If we find that the
O
H3C
product is
S
O
O
18
OCH2CH3
, and the compound
H3C
S
O
OCH2CH3
is not
detected. Then it will prove that the formation of alkyl sulfonate does not cause cleavage at the
C－O bond of the alcohol.
11.14 Starting with the appropriate sulfonic acid and PCl3, or with the appropriate sulfonyl
chloride, show how you would prepare (a) methyl p-toluensulfonate, (b) isobutyl
methanesulfonate, and (c) tert-butyl methanesulfonate.
Solution:
(a)
CH 3
CH 3
+
O
S
CH3 OH
O
O
Cl
S
O
OCH 3
(b)
O
O
H3C
S
Cl
+
(CH3)2CHCH2OH
H3C
S
OCH2CHCH3
O
O
CH3
(c)
O
O
H3C
S
Cl
H3C
+ (CH3)3 COH
S
O
C(CH3)3
O
O
11.15 Show the configurations of products formed when (a) (R)-2-butanol is converted to a
tosylate, and (b) when this tosylate reacts with hydroxide ion by an SN2 reaction. (c) Converting
cis-4-methylcyclohexanol to a tosylate and then allowing the tosylate to react with LiCl (in an
appropriate solvent) yields trans-1-chloro-4-methylcyclohexane. Outline the stereochemistry of
these steps.
Answer:
(a)
O
OH
+
H
O
H
base
S
O
Cl
(- HCl)
S
O
O
(b)
O
S
H
O
H
OH-
O
S
SN 2
O
O
+
OH
O
(c)
OH
OTs
TsOH
Cl
base
Cl-
11.16 (a) What factor explains the observation that tertiary alcohols react with HX faster than
secondary alcohols? (b) What factor explains the observation that methanol reacts with HX faster
than a primary alcohol?
Answer:
(a) Because they are SN1 reactions, the tertiary alcohols can lead to tertiary carbocation and it is
more stable than secondary carbocation.
(b) Because they are SN2 reactions, the hindrance of methyl group is smaller than a primary
alcohol.
11.17 Treating 3-methyl-2-butanol (see following reaction) with HBr
2-bromo-2-methylbutane as the sole product. Outline a mechanism for the reaction.
CH3
yields
CH3
CH3CHCHCH3
HBr
CH3CCH2 CH3
Br
OH
2-Bromo-2-methylbutane
3-Methyl-2-butanol
Answer:
CH3
CH3
CH3CHCHCH3
OH
H
CH3CHCHCH3
+
OH2
H3C
CH3CH
CH3
CHCH3
C
rearrangement
CH2CH
3
H3C
Br
T.M.
11.18 An exception to what we have just said has to do with syntheses of unsymmetrical ethers in
which one alkyl group is a tert-butyl group and the other group is primary. This synthesis can be
accomplished by adding tert-butyl alcohol to a mixture of the primary alcohol and H2SO4 at room
temperature. Give a likely mechanism for this reaction and explain why it is successful.
Answer:
H
R3 C
O
H
+
H
R3 C
OSO3H
O
H
R3C
H
RH2C
O
H
+
R 3C
R3C
O
CH2R
R3C
O
CH2R
H
R3 C
O
CH2R + H2O
11.19: (a) Outline two methods for preparing isopropyl methyl ether by a Williamson synthesis. (b)
One method gives a much better yield of the ether than the other. Explain which is the better
method and why.
Answer:
(1)
CH3
CH3
CH3CHONa
+ CH3CH2 Br
CH3CHOCHCH2
(2)
CH3
CH3CH2ONa
CH3CH
+
Br
CH3CHOCHCH2
CH3
Method (1) gives a much better yield of the ether, because the secondary carbon is more
easily attacked than the tertiary carbon in method (2).
11.20 The two synthesis of 2-ethoxy-1-phenylpropane shown here give products with opposite
optical rotations.
C6 H5 CH2CHCH3
K
potassium
alkoxide
+H2
C2H5Br
-KBr
C6H5CH2CHCH3
OC2H5
OH
[α]=+23.5°
[α]=+33.0°
TsCl/base(Ts=p-toluenesulfonyl)
C6H5CH2CHCH3
OTs
C2H5OH
C6H5CH2CHCH3
K2CO3
OC2H5
[α]=-19.9°
How can you explain this result?
Answer: When potassium alkoxide attacks C2H5Br, the configuration of the chiral carbon is
unchanged. However, when the starting material is dealt with TsCl ,the oxygen of the ethanol
attacks the chiral carbon form the backside and then the OTs group leaves. Therefore the optical
rotation is opposite.
11.21 Write a mechanism that explains the formation of tetrahydrofuran (THF) from the reaction
of 4-chloro-1-butanol and aqueous sodium hydroxide.
Answer:
HO
Cl
O
O
Cl
11.22 Epoxides can be synthesized by treating halohydrins with aqueous base. For example,
treating ClCH2CH2OH with aqueous sodium hydroxide yields ethylene oxide. (a) Propose a
mechanism for this reaction. (b) trans-2-Chlorocyclohexanol reacts readily with sodium hydroxide
to yield cyclohexene oxide. Cis-2-Chloro-cyclohexanol does not undergo this reaction, however.
How can you account for this difference?
Answer:
Cl
(a)
H2C
OHCH2CH2 Cl
O
(b)
CH2
O
trans-2-Chlorocyclohexanol
Cl
O
O
cis-2-Chlorocyclohexanol
Backsidec attack is not possible with the cis-isomer, therefore, it doesn't form an epoxide
11.23 (a) The mechanism for the formation of the tert-butyl ether from a primary alcohol and
isobutylene is similar to that discussed in Problem 11.8. Propose such a mechanism. (b) What
factor makes it possible to remove the protecting tert-butyl group so easily? (Other ethers require
much more forcing conditions for cleavage, as we shall see in Section 11.16.) (c) Propose a
mechanism for the removal of the protecting tert-butyl group.
Solution:
(a)
H+
H2C
RCH2OH
C
CH3
H3C
CH3
CH3
C
CH3
RH2C
CH3
O
C
C
CH3
H
CH3
H2 O
CH3
RH2 C
O
CH3
CH3
(b) When the ether is protonated, because the tert-butyl cation is stable, so it is a better leaving
group, it can leave easily in the dilute acid condition.
(c)
H+
RH2C
O
CH3
C
CH3
CH3
RH2C
CH3
XRH2 C
OH +
O
C
CH3
H
CH3
CH3
+C
CH3
CH3
CH3
X
C
CH3
CH3
11.24 When am ether is treated with cold concentrated HI, cleavage occurs as follows:
ROH +RI
R-O-R + HI
When mixed ethers are used, the alcohol and alkyl iodide that form depend on
the nature of the alkyl groups. Explain the following observations.
(a) When
(R)-2-methoxybutane reacts, the products are methyl iodide and (R)-2-butanol. (b) When
tert-butyl methyl ether reacts, the products are methanol and tert-butyl iodide.
Solution:
(a) This reaction undergoes a SN2 mechanism, first (R)-2-methoxybutane protonated, because
of the steric hindrance, the iodine anion attacks the methyl group, then (R)-2-butanol
formed.
(b) This reaction undergoes a SN1 mechanism, because tert-butyl cation can exist stably, in
this reaction it leaves after that tert-butyl methyl ether protonated, and the iodine anion
attaches to the cation to form tert-butyl iodide.
11.25 Propose structures for each of the following products:
(a) Oxirane
HA
CH3OH
C3H8O(an industrial solvent called Methyl Cellosolve)
HA
CH3CH2 OH C4H10O2(Ethyl Cellosolve)
KI
H2O
C2H4 IO
NH3
C2H7 NO
CH3ONa
CH3OH C3H8O
(b) Oxirane
(c) Oxirane
(d) Oxirane
(e) Oxirane
O
OH
(a)
O
OH
(b)
I
OH
(c)
H2 N
OH
(d)
O
OH
(e)
C(CH3)2
H2 C
O
11.26 Treating 2.2-dimethyloxirane,
, with sodium methoxide in methanol
gives primarily 1-methoxy-2-methyl-2-propanol. What factor accounts for this result?
Hydrolysis by base should consider the steric hindrance
HOMe
O
O
C(CH3)2
H 2C
HO
O
OMe
O
11.27 When sodium ethoxide reacts with 1-(chloromethyl) oxirane, labeled with 14C as shown by
the asterisk in I, the major product is an epoxide bearing the label as in II. Provide an explanation
for this reaction.
Cl
CH2
*CH2
CH
O
Ⅰ
1-(Chloromethyl)oxirane
(epichlorohydrin)
Solution:
NaOC2 H5
H2 C
*CH
CH
O
2
Ⅱ
OCH3
O
OC2H5
Cl
CH2
*
CH
2
CH
H2C
*
CH OCH
CH
2
H2C
3
O
O
Cl
*
CH
2
CH
OCH3
Ⅱ
11.28 Outline a mechanism similar to the one just given that shows how the enantiomeric form of
trans-1, 2-cyclopentanediol is produced.
Solution:
H
H
H
H
O
O +
H
H
OH
H
OH
OH
H
H
O
H
H
H
H
H
H
O
H
O
OH
trans-1,2-cyclopentanediol
H
11.29 Outline a scheme such as the one shown in Fig.11.5 showing how the reaction of
CH3(CH2)6CH2Cl with cyanide ion (just shown) takes place by phase-transfer catalysis. Be sure to
indicate which ions are present in the organic phase, which are in the aqueous phase, and which
pass from one phase to the other.
Answer:
Aqueous Phase
CNCN-
+
Cl+
Q+X-
Q+CN-
Q+X+
CH3(CH2)6CH2CN
Q+CN+
CH3(CH2)6CH2Cl
Q+X-
CH3 (CH2)6 CH2 Cl
Organic Phase
11.30 write structures for (a) 15-crown-5 and (b) 12-crown-4.
Answer:
(a)
O
O
15
O
O
O
(b)
O
12
O
O
O
11.31 Give an IUPAC substitutive name for each of the following alcohols:
OH
(a) (CH3 )3CCH2 CH2 OH
(e)
CH3
CH3
(b)
H2C
(c)
HOCH2CHCH2CH2OH
CHCH2CHOH
H
H
(f)
CH3
(d)
CH3
C6H5CH2CH2 OH
HO
Answer:
(a) 3,3-dimethylbutanol (b) 4-penten-2-ol
(c) 2-methyl-butane-1, 4-diol
(d) 2-phenyl-enthanol
(e) 1-methyl-cyclopent-2-enol
(f) cis-3-methyl-cyclohextanol
11.32 Write structural formulas for each of the following:
(a) (Z)-2-Buten-1-ol
(f) Tetrahydrofuran
(b) (R)-1,2,4-Butanetriol
(g) 2-Ethoxypentane
(c) (1R,2R)-1,2-Cyclopentanediol (h) Ethyl phenyl ether
(d) 1-Ethylcyclobutanol
(i) Diisopropyl ether
(e) 2-Chloro-3-hexyn-1-ol
(j) 2-Ethoxyethanol
Answer:
OH
OH
(a)
OH
(b) HO
HO
HO
HO
(c)
(d)
Cl
O
(e) OH
(f)
O
(g)
O
(h)
O
(I )
(j) HO
O
11.33 Starting with each of the following, outline a practical synthesis of 1-butanol.
(a) 1-Butene (b) 1-Chlorobutane (c) 2-Chlorobutane (d) 1-Butyne
Answer:
(a)
H2
(1) THF:BH3
CH3CH2CH CH2
OH
CH3CH2CH2 C
(2) H2O2/NaOH
(b)
CH3CH2CH2 CH2Cl
NaOH/H2O
H2
CH3CH2CH2 C
OH
(c)
(1)t-BuOK/t-BuOH
(2)THF:BH3
CH3 CH2CHClCH3
CH3CH2CH2
(3)H2 O2/NaOH
H2
C
OH
(d)
CH3CH2C
CH
(1)H2
lindlar's catalyst
(2)THF:BH3
(3)H2O2/NaOH
CH3 CH2CH2
H2
C
11.34
Show how you might prepare 2-bromobutane from
(c) 1-Butene
(a) 2-Butanol, CH3CH2CHOHCH3
(d) 1-Butyne
(b) 1-Butanol, CH3CH2CH2CH2OH
Answer:
OH
(a)
CH3CH2 CHOHCH3
PBr3
CH3 CH2 CHBrCH3
(b)
(1)conc H2SO4
heat
CH3CH2CHBrCH3
CH3CH2CH2CH2OH
(2)HBr
(c)
CH3 CH2CH
HBr
CH2
CH3 CH2 CHBrCH3
(d)
(1)H2
lindlar's catalyst
CH3CH2C
CH
CH3 CH2 CHBrCH3
(2)HBr
11.35 Show how you might carry out the following transformation:
(a) Cyclohexanol → chlorocyclohexane
(b) Cyclohexene → chlorocyclohexane
(c) 1-Methylcyclohexene → 1-bromo-1-methylcyclohexane
(d) 1-Methylcyclohexene → trans-2-methylcyclohexanol
(e) 1-Bromo-1-methylcyclohexane → cyclohexylmethanol
Solution:
OH
(a)
HCl
(b)
Cl
HCl
H2SO4
heat
Cl
Br
(c)
(d)
CH3
HBr
CH3
1)B2H6
2)-OH/H2O2
CH3
(CH3)3 O△
CH3
OH
CH3
Br
(e)
CH2
H2
C
Br
OH-
HBr
ROOR
C
H2
OH
11.36 Give the structures and acceptable names for the compounds that would be formed when
1-butanol is treated with each of the following reagents:
(a) Sodium hydride
(b) Sodium hydride, then 1- bromopropane
(c) Methanesulfonyl chloride and base
(d) p-Toluenesulfonyl chloride
(e) Product of (c), then sodium methoxide
(f) Product of (d), then KI
Solution:
(g) Phosphorus trichloride
(h) Thionyl chloride
(i) Sulfuric acid at 140℃
(j) Refluxing concentrated HBr
(k) tert-Butylchlorodimethylsilane
(l) Product of (k), then fluoride ion
(a) CH3CH2CH2CH2OH + NaH
CH3CH2CH2CH2ONa + H2
Name of the product: Sodium butoxide.
CH3CH2 CH2 Br
NaH
(b) CH3CH2CH2 CH2 OH + NaH
CH3CH2CH2CH2OCH2 CH2CH3
Name of the product: Butyl propyl ether.
O
(c) CH3CH2CH2CH2OH + H3C
O
Cl
S
base
H3C
O
OCH2CH2CH2CH3
S
O
Name of the product: Butyl methanesulfonate.
O
O
(d)H3C
Cl
S
CH3(CH2)3OH
S
H3C
OCH2CH2CH2CH3
O
O
Name of the product: Butyl p-toluenesulfonate.
O
(e) H3C
S
OCH2 CH2CH2CH3
+ CH3ONa
CH3OCH2CH2 CH2 CH3
O
Name of the product: Butyl methyl ether.
O
(f) H3C
S
OCH2CH2CH2CH3
KI
CH3CH2 CH2 CH2I
O
Name of the product: 1- iodobutane.
(g) CH3CH2CH2CH2OH
PCl3
CH3CH2CH2CH2Cl
Name of the product: 1- chlorobutane
(h) CH3CH2CH2CH2 OH
SOCl2
CH3 CH2 CH2CH2Cl
Name of the product: 1- chlorobutane
(i) CH3 CH2 CH2CH2OH
H2 SO4
140℃
Name of the product: Dibutyl ether.
CH3CH2CH2CH2 OCH2CH2CH2CH3
HBr
(j) CH3CH2CH2CH2OH
Refluxing CH3CH2CH2CH2Br
Name of the product: 1- bromobutane.
(k) H3C
CH3
CH3
C
Si
CH3
CH3
Cl + CH3 CH2 CH2CH2OH
H3C
CH3
CH3
C
Si
CH3
CH3
OCH2 CH2CH2CH3
Name of the product: tert-Butylbutyldimethylsilyl butyl ether
(l)
H3C
CH3
CH3
C
Si
CH3
CH3
OCH2CH2CH2CH3
F- CH CH CH CH OH + H C
3
3
2
2
2
CH3
CH3
C
Si
CH3
CH3
F
Name of the product: tert-Butylfluorodimethylsilane.
11.37 Give the structures and names for the compounds that would be formed when 2-butanol is
treated with each of the reagents in Problem 11.36.
Answers:
O
(a) CH3CHCH2CH3
(b) CH3CHOCH2CH2CH3
ONa
(c) H3CS
C 2H5
Sodium isobutoxide
(d) H3C
Isobutyl methanesulfonate
CH3
S
(e) H3CO
OCHCH2CH3
Isobutyl p-methantoluenesulfonate
Isobutyl methyl ether
(g) CH3CHCH2CH3
I
(h) CH3CHCH2CH3
Cl
Cl
2-Iodobutane
2-Chlorobutane
(i) H3CHC
(j) CH3CHCH2CH3
CHCH3
CHCH2CH3
CH3
O
(f) CH3CHCH2CH3
OCHCH2CH3
O
Isobutyl propyl ether
O
CH3
2-Chlorobutane
Br
2-Butene
2-Bromobutane
CH3
(k) CH3CH2CHO
CH3
Si
C(CH3)3
CH3
tert-Butylisobutoxydimethylsilane
(l) CH3CHCH2CH3
OH
2-Butanol
11.38 What compounds would you expect to be formed when each of the following ethers is
refluxed with excess concentrated hydrobromic acid?
(a) Ethyl methyl ether
(c) Tetrahydrofuran
(d) 1,4-Dioxane
(b) tert-Butyl ethyl ether
Answers:
(a) CH3CH2Br and CH3Br
(b) t-BuBr and CH3CH2Br
(c) BrCH2CH2CH2CH2Br
(d) BrCH2CH2Br
11.39 Write a mechanism that accounts for the following reaction:
OH
HA
+
HOH
Answer:
H+
OH
OH
2
H
11.40 Show how you would utilize the hydroboration-oxidation procedure to prepare each of the
following alcohols:
(a) 3,3-Dimethyl-1-butanol
(1)B2H6,THF
(2) H2O2/OH-
HO
(b) 1-Hexanol
(1)B2 H6 ,THF
(2) H2 O2/OH-
HO
(c) 2-Phenylethanol
(1)B2H6,THF
(2) H2O2 /OH-
OH
(d) trans-2-Methylcyclopentanol
(1)B2H6,THF
H
CH3
H
(2) H2O2 /OH-
CH3
HO
H
11.41 Write a three-dimensional formula for the product formed when 1-mehtylcyclo-hexene is
treated with each of the following reagents. In each case, designate the location of deuterium of
tritium atoms.
(a) (1) THF:BH3,(2)CH3CO2T
(b) (1) THF:BH3,(2)CH3CO2D
(c) (1)THF:BD3,(2)NaOH,H2O2,H2O
Answer:
D
D
T
(a)
(b)
D
(c)
OH
11.42 Starting with isobutane show how each of the following could be synthesized. (You need not
repeat the synthesis of a compound prepared if an earlier part of this problem.)
(a) tert-Butyl bromide
(b) 2-Methylpropene
(c) Isobutyl bromide
(d) Isobutyl iodide
(e) Isobutyl alcohol (two ways)
(f) tert-Butyl alcohol
(g) Isobutyl methyl ether
CH3
O
(h) CH3CHCH2 OCCH3
CH3
(i) CH3CHCH2CN
CH3
(j) CH3CHCH2SCH3 (two ways)
CH3
CH3 CCH2CBr3
(k)
Br
Answer:
Br
+ Br2
(a)
Base
Br
-HBr
(b)
HBr
Br
R2O2
(c)
NaI
Br
I
(d)
1, BH3
OH
2, OH- / H2O2
(e)
Br
OH
H 2O
(f)
1. Na
O
OH
2. CH3I
(g)
OH
CH3COCl
O
Et3N
O
(h)
Br
NaCN
Br
CH3SNa
CN
(i)
S
(j)
BrCBr3
CBr3
R2O2
Br
(k)
11.43 Vicinal halo alcohols (halohydrins) can be synthesized by treating epoxides with HX. (a)
Show how you would use this method to synthesize 2-chlorocyclopentanol from cyclopentene. (b)
Would you expect the product to be cis-2-chlorocyclopentanol or trans-2-chlorocyclopentanol;
that is , would you expect a net syn addition or a net anti addition of －Cl and －OH? Explain.
Answer: (a)
OH
HO
O
R
C
O
OH
HCl
O
Cl
+
Cl
(b) It should be trans-2-chlorocyclopentanol.
11.44 Outline below is a synthesis of the gypsy moth sex attractant E ( a type of pheromone, see
Section 4.16). Give the structures of E and the intermediates A-D in the synthesis.
HC
CNa
1-Bromo-5-methylhexane A(C H ) NaNH2
9 16
liq. NH3
liq. NH3
H2
Ni2B(P-2)
D(C19 H38 )
C6H5CO3 H
1-Bromodecane
B(C9 H15Na)
C(C19 H36)
E(C19 H38O)
Answer:
HC
CNa
1-Bromo-5-methylhexane
HC
liq. NH3
C(CH2)4CH(CH3 )2
NaNH2
NaC
liq. NH3
H
1-Bromodecane
CH3(CH2)9C
C(CH2)4CH(CH3)2
C(CH2)4CH(CH3)2
H
H2
Ni2B(P-2)
H3C(H2C)9
(CH2)4CH(CH3)2
O
C6H5CO3H
(CH2)4CH(CH3)2
H3C(H2C)9
H
H3C(H2C)9
H
+
(CH2)4CH(CH3 )2
H
H
O
11.45 Starting with 2-methylpropene (isobutylene) and using any other needed reagents, outline a
synthesis of each of the following:
(a) (CH3)2CHCH2OH
(c) (CH3)2CDCH2T
(b) (CH3)2CHCH2T
(d) (CH3)2CHCH2OCH2CH3
CH3
Answer: (a) H2C
CH3
1) B2 H6
2) H2 O2,OH-
CCH3
CH3CHCH2OH
CH3
H2C
1. BH3
CCH3
(b)
CH3
(c)
(d)
H2C
CH3
H2C
CCH3
1. BD3
CCH3
(CH3 )2CHCH2T
2. CH3 COOT
(CH3)2CDCH2T
2. CH3COOT
CH3
1) B2 H6
2) H2O2,OH
-
1. NaOEt
2. EtBr
CH3CHCH2OH
(CH3)2CHOCH2CH3
11.46 Show how you would use oxymercuration-demercuration to prepare each of the following
alcohols from the appropriate alkene:
(a) 2-Pentanol
(c) 3-Methyl-3-pentanol
(b) 1-Cyclopentylethanol
(d) 1-Ethylcyclopentanol
Answer:
(a)
(c)
(b)
(d)
11.47 Give stereochemical formulas for each product A-L and answer the questions given in parts
(b) and (g).
(1) THF:BH3
(a) 1-Methylcyclobutene
(2) H2O2,OH
A(C5 H10 O)
-
TsCl
OH-
B (C12 H16SO3)
OH-
(b) What is the stereoisomeric relationship between A and C?
(c) B (C12H 16SO3 )
I-
D(C5 H9I)
(d) trans-4-Methylcyclohexanol
(e) (R)-2-Butanol
(f) (R)-2-Butanol
NaH
MsCl
MsCl
-
OH
H(C4H9ONa)
K(C5H12SO3)
E(C8H16 SO3)
CH3 I
CH3ONa
HC
CNa
J(C5H12O)
L(C5H12O)
F(C9H14)
C(C5H10 O)
(g) What is the stereoisomeric relationship between J and L?
A:
CH3
H
H
CH3
CH3
H
H
CH3
H
OH
OH
H
H
OTs
OTs
H
A
B
CH3
OH
OH
CH3
CH3
I
CH3
I
H
H
H
H
H
H
H
H
C
D
(b) A and C are diastereomers.
H
H
O
Me
Ms
H
Me
H
H
F
E
C2H5
Na O
C2H5
C2H5
OCH3
MsO
H3CO
Me
C2H5
H
Me
H
Me
H
K
J
Me
H
L
(g) J and L are enantiomers.
11.48 When the 3-bromo-2-butanol with the stereochemical structure A is treated with
concentrated HBr it yields meso-2,3-dibromobutane; a similar reaction of the 3-bromo-2-butanol
B yields (+-)-2,3-dibromobutane. This classic experiment performed in 1939 by S. Winstein and
H.J.Lucas was the starting point for a series of inverstingations of what are called neighboring
rgroup effects. Propose mechanisms that will account for the stereochemistry of these reactions.
Br
H
CH3
H
H
H3C
OH
a
Answer:
A:
Br
CH3
H
H3C
OH
b
Br
CH3
H
H
Br
Br
CH3
H
H
CH3
H
Br
H
H3C
CH3
Br
H
H3C
H
OH
Br
H3C
H3C
OH2
H
H
Br
H3C
Br
CH3
Br
H
B:
Br
H
CH3
Br
Br
H
H
CH3
H3C
CH3
H
H
H3C
H
Br
OH
H3C
H
H3C
OH2
CH3
Br
H
Br
H
H
Br
H3C
H
Br
Br
CH3
11.49 Reaction of an alcohol with thionyl chloride in the present of a tertiary amine (e.g..pyridine)
affords replacement of the OH group by Cl with the inversion of configuration (Section 11.14).
However, if the amine is omitted, the result is usually replacement with retention of configuration.
The same chlorosulfite intermediate is involved in both cases. Suggest a mechanism by this
intermediate can give the chloro product without inversion.
Answer:
With amine:
R3
R1
O
C
+
OH
R1
S
Cl
R2
R3
H
O
C
O
S
Cl
Cl
R2
R2
O
R1C
O
- Cl
Cl
O
S
RH2C
O
S
Cl
+
HCl
Cl
R3
R3N
H
+
Cl
R3NH Cl
HCl
O
O
Cl
+
RH2C
O
S
Cl
SN2 mechanim
inversion of
the configuration
Without amine:
RCH2Cl
S
+
O
RCH2Cl
Cl
chlorosulfite
+
SO2
+ Cl
R3
R1
C
O
OH
+
R1
S
Cl
R3
H
O
C
O
S
O
R2
R1C
O
S
H
Cl
- Cl
Cl
Cl
R2
R2
Cl
R3
Cl
C
R1C
R3
O
S
Cl
SN i mechanism
retension of the
configuration
R3
R1
O
R2
Cl
+ SO2
R2
11.50 Draw the stereoisomers that are possible for the compound 1,2,3-cyclopentanetriol. Label
their stereocenters and say which are enantiomers and which are diastereomers. [Some of the
isomers contain a “pseudoasymmetric center,” one that has two possible configurations, each
affording a different stereoisomer, each of which is identical to its mirror image. Such
stereoisomers can only be distinguished by the order of attachment of R versus S groups at the
pseudoasymmetric center. Of these the R group is given higher priority than the S, and this permits
assignment of configuration as r or s, lower case letters being used to designate the
pseudoasymmetry.]
Answer:
OH
∗
OH
∗
OH
∗
∗
OH
A
OH
OH
∗
OH
B
∗
∗
OH OH
OH
∗ ∗
OH
∗
OH
C
D
The stereocanters are marked with *. B and C are enantiomers. AB, AC, AD, BD, CD are
diastereomers.