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Ch. 9 Alcohols, Epoxides,

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Alcohols contain an OH group bonded to an sp3 hybridized C. sp3 ... benzo[a]pyrene. diol epoxide. Oxidation increases water solubility. Epoxides and Cancer ... – PowerPoint PPT presentation

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Title: Ch. 9 Alcohols, Epoxides,


1
Ch. 9 Alcohols, Epoxides, Ethers
diethyl ether
ethylene glycol
glucose
DGEBA
brevetoxin B
2
Structure of Alcohols
Alcohols contain an OH group bonded to an sp3
hybridized C
sp3 hybridized C
3
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
4
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)
5
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
6
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
7
Properties of Alcohols
sp3 hybridized
d-
d
d
109o
8
Properties of Alcohols
9
Which has the highest boiling point?
A B
C
D E
10
Properties of Alcohols
Alcohols can act as acids or bases
pKa 16 (weak acid)
11
Properties of Alcohols
Alcohols are weak bases
12
Preparation of Alcohols
Primary alcohols can be prepared by SN2 reactions
Example-
13
Reactions of Alcohols
1. Dehydration loss of H2O to produce an alkene
Order of reactivity 3o gt 2o gt 1o
14
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
15
Dehydration Reactions of Alcohols
A. Acid-catalyzed dehydration treatment with
strong acids (H2SO4, p-toluenesulfonic acid,
etc) results in dehydration
Example
major minor
16
Here is how it happens
17
The major product of this reaction is
A B C
D E
18
The major product of this reaction is
A B
C
D E
19
Dehydration Reactions of Alcohols
Carbocation rearrangements can result in
unexpected products
Rearrangements occur by 1,2-hydride shifts
and 1,2-alkyl shifts
20
Here is what happens.
21
What is the major product?
A B
C
D E
22
Dehydration Reactions of Alcohols
B. Dehydration with POCl3/Pyridine reaction
proceeds by E2 mechanism
Zaitsev product is favored
23
What is the major product?
A B
C
D E
24
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
25
Conversion of Alcohols to Alkyl Halides
26
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27
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
28
Conversion of Alcohols to Alkyl Halides
29
Which is the major product?
A B
C
D E
30
Which stereoisomer is formed? A) 1 only B) 2
only C) 1 and 2
31
Conversion of Alcohols to Tosylates
3. Alcohols to tosylates
Example-
32
Reactions of Alkyl Halides/Tosylates
Conversion of OH to a better leaving group
allows substitution and elimination reactions
(Ch. 7 and 8)
33
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
34
Naming Ethers
Common names are generally used for simple
ethers List alkyl groups alphabetically
35
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
36
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
37
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
38
Preparation of Ethers
Williamson ether synthesis most common way to
prepare ethers, SN2 reaction
Example-
Is there another way? Is it better or worse?
39
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40
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
41
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42
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
43
Preparation of Epoxides
1. Intramolecular Williamson ether synthesis
starting material is a halohydrin
Example-
44
Preparation of Epoxides
2. Epoxides from Alkenes
most common method for epoxide synthesis more
detail in Ch.10
45
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
46
Reactions of Epoxides
47
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
48
Reactions of Epoxides
Mechanism has SN2 and SN1 characteristics
49
Epoxides and Cancer
benzoapyrene
diol epoxide
Oxidation increases water solubility
50
Epoxides and Cancer
dG
Epoxide ring-opening modifies DNA
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