Ch. 9 Alcohols, Epoxides,

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Ch. 9 Alcohols, Epoxides, Ethers
diethyl ether
ethylene glycol
glucose
DGEBA
brevetoxin B
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Structure of Alcohols
Alcohols contain an OH group bonded to an sp3
hybridized C
sp3 hybridized C
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Naming Alcohols
1. The parent chain must contain the OH group.
Change parent ending to -ol. 2. Give the OH
the lowest possible number.
6,6-dimethyl-3-heptanol
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Naming Alcohols
3. When the OH group is attached to a ring, it
is assumed to be at carbon 1.
2-methylcyclopentanol (NOT
2-methyl-1-cyclopentanol)
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What is the systematic name for this alcohol?
A) 2,3-diethyl-5,5-dimethyl-2-hexanol B)
4,5-diethyl-2,2-dimethyl-5-hexanol C)
4-ethyl-3,6,6-trimethyl-3-heptanol D)
4-ethyl-2,2,5-trimethyl-5-heptanol E)
1,2-diethyl-1,4,4,-trimethyl-1-pentanol
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What is the systematic name for this alcohol?
A) 7-ethyl-3,3-dimethylcycloheptanol B)
2-ethyl-6,6-dimethyl-1-cycloheptanol C)
4-ethyl-1,1-dimethylcycloheptanol D)
2-ethyl-6,6-dimethylcycloheptanol E)
7-ethyl-3-dimethylcycloheptanol
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Properties of Alcohols
sp3 hybridized
d-
d
d
109o
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Properties of Alcohols
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Which has the highest boiling point?
A B
C
D E
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Properties of Alcohols
Alcohols can act as acids or bases
pKa 16 (weak acid)
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Properties of Alcohols
Alcohols are weak bases
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Preparation of Alcohols
Primary alcohols can be prepared by SN2 reactions
Example-
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Reactions of Alcohols
1. Dehydration loss of H2O to produce an alkene
Order of reactivity 3o gt 2o gt 1o
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Rank the alcohols in order of increasing reactivit
y toward H catalyzed dehydration.
1 2 3
A) 1, 2, 3 B) 3, 2, 1 C) 2, 1, 3 D) 1, 3, 2 E) 2,
3, 1
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Dehydration Reactions of Alcohols
A. Acid-catalyzed dehydration treatment with
strong acids (H2SO4, p-toluenesulfonic acid,
etc) results in dehydration
Example
major minor
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Here is how it happens
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The major product of this reaction is
A B C
D E
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The major product of this reaction is
A B
C
D E
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Dehydration Reactions of Alcohols
Carbocation rearrangements can result in
unexpected products
Rearrangements occur by 1,2-hydride shifts
and 1,2-alkyl shifts
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Here is what happens.
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What is the major product?
A B
C
D E
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Dehydration Reactions of Alcohols
B. Dehydration with POCl3/Pyridine reaction
proceeds by E2 mechanism
Zaitsev product is favored
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What is the major product?
A B
C
D E
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Conversion of Alcohols to Alkyl Halides
2. Alcohols to alkyl halides A. Treatment of
alcohols with HX
X Cl, Br, I
Alcohol Reactivity 3o gt 2o gt 1o HX Reactivity
HI gt HBr gt HCl
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Conversion of Alcohols to Alkyl Halides
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Conversion of Alcohols to Alkyl Halides
B. Treatment of alcohols with SOCl2 and PBr3
-OH is converted to a good leaving group then
displaced by an SN2 mechanism Used for 1o and
2o alcohols
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Conversion of Alcohols to Alkyl Halides
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Which is the major product?
A B
C
D E
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Which stereoisomer is formed? A) 1 only B) 2
only C) 1 and 2
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Conversion of Alcohols to Tosylates
3. Alcohols to tosylates
Example-
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Reactions of Alkyl Halides/Tosylates
Conversion of OH to a better leaving group
allows substitution and elimination reactions
(Ch. 7 and 8)
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Structure Properties of Ethers
Ethers contain two carbon groups bonded to an
oxygen
The C-O bonds are polar, but ethers cant
hydrogen bond
Ethers are commonly used as solvents because
they are unreactive, low-boiling, and dissolve
many organic compounds
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Naming Ethers
Common names are generally used for simple
ethers List alkyl groups alphabetically
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What is the common name for this ether? A)
1-ethoxybutane B) ethyl butyl ether C) butyl
ethyl ether D) 1-butoxyethane E) ethyl propyl
ether
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Naming Ethers
Systematic naming is used for more complex
ethers Name smaller alkyl group and O as
alkoxy group
4-ethoxy-2-methylheptane
1-ethyl-2-methoxycyclohexane
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What is the systematic name? A)
6-butoxy-3-methylheptane B) 2-butyl-5-methylhepan
e ether C) 2-butoxy-5-methylheptane D)
1-butoxy-1,4-dimethylhexane E)
2-butoxy-5-ethylhexane
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Preparation of Ethers
Williamson ether synthesis most common way to
prepare ethers, SN2 reaction
Example-
Is there another way? Is it better or worse?
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Reactions of Ethers
Cleavage with HX HBr and HI cleave ethers to
form an alcohol and alkyl halide
For methyl and 1o groups, C-O cleavage occurs by
SN2 For 2o or 3o groups, C-O cleavage occurs by
SN1
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Structure Properties of Epoxides
Epoxides-cyclic ethers in which the O atom is
part of a three-membered ring
C-O-C bond angle is 60o
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Preparation of Epoxides
1. Intramolecular Williamson ether synthesis
starting material is a halohydrin
Example-
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Preparation of Epoxides
2. Epoxides from Alkenes
most common method for epoxide synthesis more
detail in Ch.10
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Reactions of Epoxides
Epoxides readily undergo ring-opening
reactions The mechanism varies with reaction
conditions 1. Opening with Strong Nucleophiles
Ring opening is SN2 Attack occurs at less
hindered position
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Reactions of Epoxides
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Reactions of Epoxides
2. Opening Under Acidic Conditions
HCl, HBr, and HI react in this way H2O and ROH
require added H Backside attack occurs at more
hindered position
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Reactions of Epoxides
Mechanism has SN2 and SN1 characteristics
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Epoxides and Cancer
benzoapyrene
diol epoxide
Oxidation increases water solubility
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Epoxides and Cancer
dG
Epoxide ring-opening modifies DNA