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Chapter 10
Alkynes
Review of Concepts
Fill in the blanks below. To verify that your answers are correct, look in your textbook at
the end of Chapter 10. Each of the sentences below appears verbatim in the section
entitled Review of Concepts and Vocabulary.
• A triple bond is comprised of three separate bonds: one ____ bond and two ____
bonds.
• Alkynes exhibit __________ geometry and can function either as bases or as
___________________.
• Monosubstituted alkynes are terminal alkynes, while disubstituted alkynes are
Review of Skills
Fill in the blanks and empty boxes below. To verify that your answers are correct, look
in your textbook at the end of Chapter 10. The answers appear in the section entitled
SkillBuilder Review.
10.1 Assembling the Systematic Name of an Alkyne
PROVIDE A SYSTEMATIC NAME FOR THE FOLLOWING COMPOUND
1) IDENTIFY THE PARENT
2) IDENTIFY AND NAME SUBSTITUENTS
3) ASSIGN LOCANTS TO EACH SUBSTITUENT
4) ALPHABETIZE
204
CHAPTER 10
10.3 Drawing the Mechanism of Acid-Catalyzed Keto-Enol Tautomerization
O
HOH
OH
H
H
OH
DRAW THE RESONANCE STRUCTURES
OF THE INTERMEDIATE
DRAW TWO CURVED ARROWS SHOWING
DEPROTONATION TO FORM THE KETONE
DRAW TWO CURVED ARROWS SHOWING
PROTONATION OF THE
BOND
π
10.5 Alkylating Terminal Alkynes
HH
IDENTIFY REAGENTS THAT WILL ACHIEVE THE FOLLOWING TRANSFORMATION:
1)
2)
3)
4)
CHAPTER 10
205
Review of Reactions
Identify the reagents necessary to achieve each of the following transformations. To
verify that your answers are correct, look in your textbook at the end of Chapter 10. The
answers appear in the section entitled Review of Reactions.
RX
XR
X
X
R
R
X
R
CH
3
O
R
O
H
RR
R R RR
R R
R OH
O
R
X
X
R
X X
X
X
C
O
O
+
Solutions
10.1.
a) 3-hexyne
206
CHAPTER 10
10.3.
10.5.
a) Yes, NaNH
2
is strong enough of a base to deprotonate a terminal alkyne.
10.6.
a) In the conjugate base of methyl amine (CH
3
NH
2
), the negative charge is associated
CHAPTER 10
207
10.7.
a)
Br
Br
H
H
H
NH
2
Br
H
H
NH
2
H
NH
2
C
HOH
208
CHAPTER 10
10.8.
C CC C
H
H
C
H
H
H
H
H
H
2-pentyne
NH
2
C CC C
H
H
C
H
H
H
H
H
C CC C
H
H
C
H
H
H
H
H
HNH
H
10.9.
a)
H
2
Lindlar's
catalyst
H
2
Pt
b)
Ni
2
B
H
2
H
2
Ni
10.10.
CHAPTER 10
209
10.11.
H
2
Lindlar's
catalyst
Na
10.12.
10.13.
a)
xs
HCl
Cl Cl
e)
Cl Cl
1) xs NaNH
2
/ NH
3
2) H
2
O
3) HBr, ROOR
Br
Br
+
210
CHAPTER 10
10.14.
Cl
Cl
Cl Cl
1) xs NaNH
2
/ NH
3
2) H
2
O
3) excess HCl
10.16.
a)
O
H O
H
H
HOHOHO
HOH
c)
OH O
H
H
HOHOHO
HOH
CHAPTER 10
211
10.17.
N
NH
H
H O
H
H
N
NH
H
HN
NH
H
H
HOH
N
N
H
H
10.18.
a)
O
b)
O
10.19.
a) b) c)
10.20.
a)
1) 9-BBN
2) H
2
O
2
, NaOH H
O
212
CHAPTER 10
10.21.
a) b) c)
10.23.
a)
O
H
Br
Br
3) 9-BBN or disiamylborane
4) H
2
O
2
, NaOH
1) xs NaNH
2
2) H
2
O
10.24.
O
4) H
2
SO
4
, H
2
O, HgSO
4
2) xs NaNH
2
3) H
2
O
1) Br
2
10.25.
a)
CHAPTER 10
213
c)
OH
O
HO
O
+
1) O
3
2) H
2
O
10.26. If ozonolysis produces only one product, then the starting alkyne must be
symmetrical. There is only one symmetrical alkyne with molecular formula C
6
H
10
:
10.27.
O
H
2
SO
4
, H
2
O
HgSO
4
10.28.
a)
1) NaNH
2
2) EtI
214
CHAPTER 10
d)
1) NaNH
2
2)
3) NaNH
2
4) MeI
I
g)
1) NaNH
2
2)
3) NaNH
2
4) EtI
I
h)
1) NaNH
2
2)
3) NaNH
2
4) MeI
I
CHAPTER 10
215
k)
1) NaNH
2
2)
3) NaNH
2
4) I
I
10.29. This process would require the used of a tertiary substrate, which is not reactive
toward S
N
2.
10.30. 4-octyne
10.31.
Br
(EtBr)
1) H
2
, Lindlar's catalyst
2) HBr
10.32.
a)
2) xs NaNH
2
1) Br
2
b)
2) xs NaNH
2
1) Br
2
216
CHAPTER 10
c)
2) dilute H
2
SO
4
OH
1) H
2
, Lindlar's catalyst
e)
Br
Br
1) NaNH
2
2) EtI
3) Na, NH
3
(l)
4) Br
2
10.33.
a)
Br
CO
2
1) NaOEt
2) Br
2
3) xs NaNH
2
4) H
2
O
5) O
3
6) H
2
O
CHAPTER 10
217
10.34.
Br
(EtBr)
1) H
2
, Lindlar's catalyst
2) HBr
10.35.
a) 2,2,5-trimethyl-3-hexyne
10.36.
a)
218
CHAPTER 10
10.37.
a)
H
2
H
2
Na
Pt
Lindlar's
Cat.
NH
3
(
l
)
10.38.
H
2
H
2
Pt
Lindlar's
Cat.
10.39.
a)
CHAPTER 10
219
10.40.
a)
O
H
2
SO
4
, H
2
O
HgSO
4
2) H
2
O
2
, NaOH
1) 9-BBN H
10.41.
Cl
HCl
(1 eq)
H
2
Pt
H
2
Lindlar's
catalyst
10.42.
a) No b) Yes c) Yes d) No e) Yes
220
CHAPTER 10
10.43.
a) No. These compounds are constitutional isomers, but they are not keto-enol tautomers
10.44.
a)
OH
b)
OH
c)
HO
10.45.
10.46.
a)
Br Br
1) excess NaNH
2
2) EtCl
3) H
2
, Lindlar's Catalyst
CHAPTER 10
221
d)
1) NaNH
2
2) MeI
3) NaNH
2
4) EtI
5) Na , NH
3
(l)
C CH H
10.47. When (R)-4-bromohept-2-yne is treated with H
2
in the presence of Pt, the
10.48.
3-ethyl-1-pentyne
10.49.
a)
222
CHAPTER 10
b)
H O
H
H
HOH
O O HH O O HH O O HH O OH
10.50.
NaNH
2
NH
3
Cl
H D
Na
D H
10.51.
a)
H
2
Pd
Compound A 2,4,6-trimethyloctane
10.52.
1) 9-BBN
2) H
2
O
2
, NaOH H
O
Compound A
CHAPTER 10
223
10.53.
a)
O
1) NaNH
2
2) Et
I
3) H
2
SO
4
, H
2
O, HgSO
4
c)
Br Br
1) excess NaNH
2
2) H
2
O
3) NaNH
2
4) MeI
5) Na, NH
3
Note: The alkyne produced after step 2 does not need to be isolated and purified, and
therefore, steps 2 and 3 can be omitted.
e)
Br Br Br
Br
1) excess NaNH
2
2) H
2
O
3) Br
2
(1 eq)
10.54.
O
H
2
SO
4
, H
2
O
HgSO
4
224
CHAPTER 10
10.55.
C C HH
3
C
10.57.
a)
1) Br
2
2) excess NaNH
2
3) H
2
O
d)
1) NaNH
2
2)
3) H
2
, Pt
I
CHAPTER 10
225
10.59.
Br
2
Br
Br
1) excess NaNH
2
2) H
2
O
10.60.
a)
Br
B
r
1) Na, NH
3
(
l
)
2) Br
2
c)
OH
+ En
1) Na, NH
3
(
l
)
2) OsO
4
, NMO
d)
1) Na, NH
3
(
l
)
2) MCPBA
226
CHAPTER 10
e)
OH
OH
+ En
1) NaNH
2
6) OsO
4
, NMO
1) NaNH
2
2) MeI
3) NaNH
f)
OH
1) NaNH
2
1) NaNH
2
2) MeI
3) NaNH
2
10.61.
a)
DD
D
2
Lindlar's Catalyst
CHAPTER 10
227
c)
D
1) NaNH
2
2) D
2
O
10.62.
10.63.
R
1
O
R
2
O
H
R
1
O
R
2
O
H
R
2
O
R
1
O
H
10.64.
N
H CH
3
NCH
3
H O
H
N
H CH
3
N
H CH
3
228
CHAPTER 10
10.65.
a)
Br
(EtBr)
1) H
2
, Lindlar's catalyst
2) HBr
b)
Br
(EtBr)
1) H
2
, Lindlar's catalyst
2) HBr
10.66.
R
Br
2
H
3
O
+
R
O
Br
Br
CHAPTER 10
229
10.67.
O
H
D O
D
D
O
H
DO
H
D
