Smith 6th (PDF - Io)

2 Work backwards. 4 Complete the synthesis.
See How To, p. 461; Sample Problems 11.8, 11.9. Try Problems 11.46–11.56.
PROBLEMS
Problems Using Three-Dimensional Models

11.24 Give the IUPAC name for each compound.
a.
b.
Page 466
11.25 Draw the enol tautomer of (a) and the keto tautomer of (b).
a.
b.
Structure and Nomenclature

11.26 Answer the following questions about erlotinib and terbinafine. Erlotinib,
sold under the trade name Tarceva, was introduced in 2004 for the
treatment of lung cancer. Terbinafine is an antifungal medication used to
treat ringworm and fungal nail infections.
a. Which C–H bond in erlotinib is most acidic?
b. What orbitals are used to form the shortest C–C single bond in
erlotinib?
c. Rank the labeled bonds in terbinafine in order of increasing bond

strength.
d. Draw two additional resonance structures for terbinafine that contain

all uncharged atoms.
11.27 Give the IUPAC name for each alkyne.
a.
b.
c.
d.
e.
f.
11.28 Give the structure corresponding to each name.

a. 5,6-dimethylhept-2-yne
b. 5-tert-butyl-6,6-dimethylnon-3-yne
c. (S)-4-chloropent-2-yne
d. cis-1-ethynyl-2-methylcyclopentane
e. 3,4-dimethylocta-1,5-diyne
f. (Z)-6-methyloct-6-en-1-yne
Tautomers
11.29 Label each pair of compounds as keto–enol tautomers or constitutional
isomers, but not tautomers.
a.
b.
c.
d.
11.30 Draw the enol form of each keto tautomer in parts (a) and (b), and the
keto form of each enol tautomer in parts (c) and (d).
a.
b.
c.
d.
Page 467
11.31 How is each compound related to A? Choose from tautomers,
constitutional isomers but not tautomers, or neither.
a.
b.
c.
d.
11.32 Enamines and imines are tautomers that contain N atoms. Draw a
stepwise mechanism for the acid-catalyzed conversion of enamine X to
imine Y.
Reactions
11.33 Draw the products formed when hex-1-yne is treated with each reagent.
a. HCl (2 equiv)
b. HBr (2 equiv)
c. Cl2 (2 equiv)
d. H2O + H2SO4 + HgSO4
e. [1] R2BH; [2] H2O2, HO−
f. NaH
g. [1] −NH2; [2] CH3CH2Br
h.
11.34 What reagents are needed to convert (CH3CH2)3CC=CH to each

compound?
a.
b.
c.
d.
11.35 Explain the apparent paradox: Although the addition of one equivalent of
HX to an alkyne is more exothermic than the addition of HX to an alkene,
an alkene reacts faster with HX.
11.36 What alkynes give each of the following ketones as the only product
after hydration with H2O, H2SO4, and HgSO4?
a.
b.
c.
11.37 What alkyne gives each compound as the only product after
hydroboration-oxidation?
a.
b.
11.38 Draw the organic products formed in each reaction.
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
Page 468
11.39 When alkyne A is treated with NaNH2 followed by CH3I, a product having
molecular formula C6H10O is formed, but it is not compound B. What is
the structure of the product, and why is it formed?
11.40 Draw the products formed in each reaction and indicate stereochemistry.
a.
b.
c.
d.
11.41 What reactions are needed to convert alcohol A to either alkyne B or

alkyne C?
11.42 Identify the lettered compounds in the following reaction scheme.

Mechanisms
11.43 One step in the synthesis of the antihistamine fexofenadine (Section
23.5) involves acid-catalyzed hydration of the triple bond in A. Draw a
stepwise mechanism for this reaction and explain why only ketone B is
formed.
11.44 Tautomerization in base resembles tautomerization in acid, but

deprotonation precedes protonation in the two-step mechanism. (a) Draw
a stepwise mechanism for the following tautomerization. (b) Then draw a
stepwise mechanism for the reverse reaction, the conversion of the keto
form to the enol.
Page 469
11.45 Draw a stepwise mechanism for each reaction.
a.
b.
Synthesis
11.46 What acetylide anion and alkyl halide are needed to synthesize each
alkyne?
a.
b.
c.
11.47 What acetylide anion and epoxide are needed to synthesize each
compound?
a.
b.
c.
11.48 Synthesize each compound from acetylene. You may use any other
organic or inorganic reagents.
a.
b.
c.
11.49 Devise a synthesis of each compound using CH3CH2CH=CH2 as the

starting material. You may use any other organic compounds or
inorganic reagents.
a.
b.
c.
d.
11.50 Devise a synthesis of the following compound from cyclohexene and

acetylene. You may use any other inorganic reagents.
11.51 Devise a synthesis of alkyne Y from alkyl bromide X, CH3I, and any
needed reagents.
11.52 Devise a synthesis of each compound. You may use HC=CH, ethylene
oxide, and alkyl halides as organic starting materials and any inorganic
reagents.
a.
b.
Page 470
11.53 Devise a synthesis of the ketone hexan-3-one, CH3CH2COCH2CH2CH3,
from CH3CH2Br as the only organic starting material; that is, all the
carbon atoms in hexan-3-one must come from CH3CH2Br. You may use
any other needed reagents.
Devise a synthesis of dodec-7-yn-5-ol from hex-1-ene
11.54 (CH3CH2CH2CH2CH=CH2) as the only organic starting material. You may
use any other needed reagents.
11.55 Devise a synthesis of each compound using CH3CH2CH2OH as the only

organic starting material: (a) CH3C=CCH2CH2CH3; (b)
CH3C=CCH2CH(OH)CH3. You may use any other needed inorganic
reagents.
11.56 Devise a synthesis of CH3CH2C=CCH2CH2OH from CH3CH2OH as the

only organic starting material. You may use any other needed reagents.
Spectroscopy
Problem 11.57 is intended for students who have already learned about
spectroscopy in Chapters A–C.
11.57 Compound Y (molecular formula C6H10) gives four lines in its 13C NMR
spectrum (27, 30, 67, and 93 ppm) and the IR spectrum given here.
Propose a structure for Y.
Additional spectroscopy problems on alkynes are given in Chapters B and C:

• Infrared spectroscopy: B.4a; B.5; B.16a; B.19a; B.21a, d; B.29
• Nuclear magnetic resonance spectroscopy: C.12a
Challenge Problems
11.58 Explain why the C=C of an enol is more nucleophilic than the C=C of an
alkene, despite the fact that the electronegative oxygen atom of the enol
inductively withdraws electron density from the carbon–carbon double
bond.
11.59 N-Chlorosuccinimide (NCS) serves as a source of Cl+ in electrophilic

addition reactions to alkenes and alkynes. Keeping this in mind, draw a
stepwise mechanism for the following addition to but-2-yne.
11.60 Draw a stepwise mechanism for the following reaction.
Page 471
11.61 Draw a stepwise mechanism for the following reaction.
11.62 Write a stepwise mechanism for each of the following reactions. Explain
why a more stable alkyne (but-2-yne) is isomerized to a less stable
alkyne (but-1-yne), but under similar conditions, 2,5-dimethylhex-3-yne
forms 2,5-dimethylhexa-2,3-diene.
11.63 Draw a stepwise mechanism for the following intramolecular reaction.

11.64 Explain why an optically active solution of (R)-α-methylbutyrophenone
loses its optical activity when dilute acid is added to the solution.

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2 Work backwards. 4 Complete the synthesis.

Problems Using Three-Dimensional Models

Structure and Nomenclature

a. Which C–H bond in erlotinib is most acidic?

c. Rank the labeled bonds in terbinafine in order of increasing bond

d. Draw two additional resonance structures for terbinafine that contain

11.27 Give the IUPAC name for each alkyne.

11.28 Give the structure corresponding to each name.

d. H2O + H2SO4 + HgSO4

e. [1] R2BH; [2] H2O2, HO−

g. [1] −NH2; [2] CH3CH2Br

11.34 What reagents are needed to convert (CH3CH2)3CC=CH to each

11.38 Draw the organic products formed in each reaction.

11.41 What reactions are needed to convert alcohol A to either alkyne B or

11.42 Identify the lettered compounds in the following reaction scheme.

11.44 Tautomerization in base resembles tautomerization in acid, but

11.49 Devise a synthesis of each compound using CH3CH2CH=CH2 as the

11.50 Devise a synthesis of the following compound from cyclohexene and

11.55 Devise a synthesis of each compound using CH3CH2CH2OH as the only

11.56 Devise a synthesis of CH3CH2C=CCH2CH2OH from CH3CH2OH as the

Additional spectroscopy problems on alkynes are given in Chapters B and C:

11.59 N-Chlorosuccinimide (NCS) serves as a source of Cl+ in electrophilic

11.60 Draw a stepwise mechanism for the following reaction.

11.63 Draw a stepwise mechanism for the following intramolecular reaction.

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