OrganicChemistry-WEB_lNotFqg-126

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PROBLEM
17-26
Acid-catalyzed dehydration of 2,2-dimethylcyclohexanol yields a mixture of
1,2-dimethylcyclohexene and isopropylidenecyclopentane. Propose a mechanism to account for
the formation of both products.
PROBLEM
17-27
Epoxides react with Grignard reagents to yield alcohols. Propose a mechanism.
PROBLEM
17-28
Treatment of the following epoxide with aqueous acid produces a carbocation intermediate that
reacts with water to give a diol product. Show the structure of the carbocation, and propose a
mechanism for the second step.
PROBLEM
17-29
Reduction of 2-butanone with NaBH4 yields 2-butanol. Is the product chiral? Is it optically active?
Explain.
PROBLEM
17-30
The conversion of 3° alcohols into 3° alkyl halides under acidic conditions involves two cationic
intermediates. For each reaction, draw the complete mechanism using curved arrows.
(a) (b)
(c)
PROBLEM
17-31
Identify the type of substitution mechanism (SN1, SN2) involved in the conversion of the following
alcohols into the corresponding alkyl halide.
(a) (b)
(c)
PROBLEM
17-32
The conversion of 3° alcohols into alkenes under acidic conditions involves two cationic
intermediates. For each reaction, draw the complete mechanism using curved arrows.
(a) (b)
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(c)
PROBLEM
17-33
For each reaction, write the mechanism using curved arrows for the conversion of the alcohol into
the corresponding alkene with POCl3. In each case, explain the regiochemistry of the elimination.
(a) (b)
(c)
PROBLEM
17-34
The trimethylsilyl (TMS) protecting group is one of several silicon protecting groups for alcohols.
For each reaction, draw the mechanism for the protection of (R)-3-bromo-1-butanol with the
following silyl chlorides, using triethylamine as the base:
(a) tert-butyldimethylsilyl chloride (TBS-Cl) (b) triisopropylsilyl chloride (TIPS-Cl)
(c) triethylsilyl chloride (TES-Cl)
PROBLEM
17-35
When the following alcohol is treated with POCl3 and pyridine, the expected elimination product
is formed. However, when the same alcohol is treated with H2SO4, the elimination product is
1,2-dimethylcyclopentene. Propose a mechanism for each pathway to account for these differences.
PROBLEM
17-36
Phenols generally have lower pKa’s than alcohols because of resonance stabilization with the
aromatic ring. Draw all of the resonance contributors for the following phenolate ions.
(a) (b) (c)
Naming Alcohols
PROBLEM
17-37
Give IUPAC names for the following compounds:
(a) (b) (c) (d)
(e) (f)
PROBLEM
17-38
Draw and name the eight isomeric alcohols with formula C5H12O.
17 • Additional Problems 609
PROBLEM
17-39
Draw structures corresponding to the following IUPAC names:
(a) Trans-3-Chlorocycloheptanol (b) 2-Ethyl-2-buten-1-ol (c) o-(2-Hydroxyethyl)phenol
(d) 3-Methyl-1-phenyl-1-butanol
PROBLEM
17-40
Bombykol, the sex pheromone secreted by the female silkworm moth has the formula C16H28O
and the systematic name (10E,12Z)-10,12-hexadecadien-1-ol. Draw bombykol, showing the correct
geometry for the two double bonds.
PROBLEM
17-41
Carvacrol is a naturally occurring substance isolated from oregano, thyme, and marjoram. What is
its IUPAC name?
Synthesizing Alcohols
PROBLEM
17-42
What Grignard reagent and what carbonyl compound might you start with to prepare the following
alcohols:
(a) (b) (c) (d)
(e) (f)
PROBLEM
17-43
What carbonyl compounds would you reduce to prepare the following alcohols: List all possibilities.
(a) (b) (c)
PROBLEM
17-44
What carbonyl compounds might you start with to prepare the following compounds by Grignard
reaction? List all possibilities.
(a) 2-Methyl-2-propanol (b) 1-Ethylcyclohexanol (c) 3-Phenyl-3-pentanol
(d) 2-Phenyl-2-pentanol (e) (f)
PROBLEM
17-45
How would you synthesize the following alcohols, starting with benzene and other alcohols of six or
fewer carbons as your only organic reagents?
(a) (b) (c)
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(d)
Reactions of Alcohols
PROBLEM
17-46
What products would you obtain from reaction of 1-pentanol with the following reagents:
(a) PBr3 (b) SOCl2 (c) Dess–Martin periodinane
PROBLEM
17-47
How would you prepare the following compounds from 2-phenylethanol: More than one step may
be required.
(a) Styrene (PhCH CH2) (b) Phenylacetaldehyde (PhCH2CHO)
(c) Phenylacetic acid (PhCH2CO2H) (d) Benzoic acid (e) Ethylbenzene (f) Benzaldehyde
(g) 1-Phenylethanol (h) 1-Bromo-2-phenylethane
PROBLEM
17-48
How would you prepare the following compounds from 1-phenylethanol: More than one step may
be required.
(a) Acetophenone (PhCOCH3) (b) Benzyl alcohol (c) m-Bromobenzoic acid
(d) 2-Phenyl-2-propanol
PROBLEM
17-49
How would you prepare the following substances from cyclopentanol: More than one step may be
required.
(a) Cyclopentanone (b) Cyclopentene (c) 1-Methylcyclopentanol
(d) trans-2-Methylcyclopentanol
PROBLEM
17-50
What products would you expect to obtain from reaction of 1-methylcyclohexanol with the
following reagents?
(a) HBr (b) NaH (c) H2SO4
Spectroscopy
PROBLEM
17-51
The following 1H NMR spectrum is that of an alcohol, C8H10O. Propose a structure.
PROBLEM
17-52
Propose structures for alcohols that have the following 1H NMR spectra:
17 • Additional Problems 611
(a) C5H12O
(b) C8H10O
PROBLEM
17-53
Propose a structure consistent with the following spectral data for a compound C8H18O2:
IR: 3350 cm–1
1H NMR: 1.24 δ (12 H, singlet); 1.56 δ (4 H, singlet); 1.95 δ (2 H, singlet)
PROBLEM
17-54
The 1H NMR spectrum shown is that of 3-methyl-3-buten-1-ol. Assign all the observed resonance
peaks to specific protons, and account for the splitting patterns.
PROBLEM
17-55
A compound of unknown structure gave the following spectroscopic data:
Mass spectrum: M+ = 88.1
IR: 3600 cm–1
1H NMR: 1.4 δ (2 H, quartet, J = 7 Hz); 1.2 δ (6 H, singlet); 1.0 δ (1 H, singlet); 0.9 δ (3 H, triplet,
J = 7 Hz)
13C NMR: 74, 35, 27, 25 δ
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