Transcript Reactions of Alcohols - Welcome to Terry Sherlock's Web Site

CH3CH2CH2
H
C O
H
H H
CHE 242
Unit V
Structure and Reactions of
Alcohols, Ethers and
Epoxides; Basic Principles of
NMR Spectroscopy
Br
CHAPTER ELEVEN
Terrence P. Sherlock
Burlington County College
2004
CH3CH2CH2
Br
Types of Alcohol Reactions
•
•
•
•
•
•
•
Dehydration to alkene
Oxidation to aldehyde, ketone
Substitution to form alkyl halide
Reduction to alkane
Esterification
Tosylation
Williamson synthesis of ether
Chapter 11
H
C O
H
H H
=>
2
CH3CH2CH2
Br
Summary Table
Chapter 11
H
C O
H
H H
3
=>
CH3CH2CH2
1º, 2º, 3º Carbons
Br
H
C O
H
H H
=>
Chapter 11
4
CH3CH2CH2
Br
Oxidation of 2° Alcohols
•
•
•
•
H
C O
H
H H
2° alcohol becomes a ketone
Reagent is Na2Cr2O7/H2SO4
Active reagent probably H2CrO4
Color change: orange to greenish-blue
OH
CH3CHCH2CH3
Na2Cr2O7 / H2SO4
O
CH3CCH2CH3
=>
Chapter 11
5
CH3CH2CH2
Oxidation of 1° Alcohols
Br
H
C O
H
H H
• 1° alcohol to aldehyde to carboxylic acid
• Difficult to stop at aldehyde
• Use pyridinium chlorochromate (PCC)
to limit the oxidation.
• PCC can also be used to oxidize 2°
alcohols to ketones.
OH
N H CrO3Cl
CH3CH2CH2CH2
O
CH3CH2CH2CH
=>
Chapter 11
6
CH3CH2CH2
3° Alcohols Don’t Oxidize
Br
H
C O
H
H H
• Cannot lose 2 H’s
• Basis for chromic acid test
Chapter 11
=>
7
CH3CH2CH2
Br
Alcohol as a Nucleophile
H
C
H
C O
H
H H
O
R X
• ROH is weak nucleophile
• RO- is strong nucleophile
• New O-C bond forms, O-H bond breaks.
=>
Chapter 11
8
CH3CH2CH2
Alcohol as an Electrophile
• OH- is not a good
leaving group unless it
is protonated, but most
nucleophiles are strong
bases which would
remove H+.
• Convert to tosylate
(good leaving group) to
react with strong
nucleophile (base)
Br
H
C O
H
H H
H
+
C
O
C-Nuc bond forms,
C-O bond breaks
=>
Chapter 11
9
CH3CH2CH2
Br
Formation of Tosylate Ester
H
C O
H
H H
H
C
O
C
C
H O
O
Cl
O
S
O
N
O
CH3
S
O
CH3
p-toluenesulfonyl chloride
TsCl, “tosyl chloride”
Chapter 11
O
S
O
CH3
ROTs,
a tosylate ester
=>
10
CH3CH2CH2
Br
SN2 Reactions of Tosylates
•
•
•
•
•
•
H
C O
H
H H
With hydroxide produces alcohol
With cyanide produces nitrile
With halide ion produces alkyl halide
With alkoxide ion produces ether
With ammonia produces amine salt
With LiAlH4 produces alkane
=>
Chapter 11
11
CH3CH2CH2
Summary of Tosylate
Reactions
Br
H
C O
H
H H
=>
Chapter 11
12
CH3CH2CH2
Reduction of Alcohols
Br
H
C O
H
H H
• Dehydrate with conc. H2SO4, then add H2
• Tosylate, then reduce with LiAlH4
OH
CH3CHCH3
H2SO4
alcohol
OH
CH3CHCH3
alcohol
CH2
CHCH3
H2
Pt
alkene
TsCl
CH3CH2CH3
alkane
OTs
CH3CHCH3
tosylate
Chapter 11
LiAlH4
CH3CH2CH3
alkane
=>
13
CH3CH2CH2
Br
Reaction with HBr
•
•
•
•
H
C O
H
H H
-OH of alcohol is protonated
-OH2+ is good leaving group
3° and 2° alcohols react with Br via SN1
1° alcohols react via SN2
R O H
H3O
+
H
R O H
Chapter 11
-
Br
R
Br
=>
14
CH3CH2CH2
Mechanism with PBr3
Br
H
C O
H
H H
• P bonds to -OH as Br leaves
• Br- attacks backside (S 2)
N
• HOPBr2 leaves
Chapter 11
=>
15
Reaction with
Thionyl Chloride
•
•
•
•
CH3CH2CH2
Br
H
C O
H
H H
Produces alkyl chloride, SO2, HCl
S bonds to -OH, Cl leaves
Cl- abstracts H+ from OH
C-O bond breaks as Cl transferred to C
Chapter 11
16
=>
CH3CH2CH2
Periodic Cleavage
of Glycols
Br
H
C O
H
H H
Same products formed as from ozonolysis
of the corresponding alkene.
CH3
H
CH3
C
C CH3
OH
OH
HIO4
CH3
CH3
H
C
+
O
O
C CH3
O3
(CH3)2S
OsO 4
H2O 2
H
C
H3C
C
CH3
=>
CH3
Chapter 11
17
CH3CH2CH2
Br
Fischer Esterification
H
C O
H
H H
• Acid + Alcohol yields Ester + Water
• Sulfuric acid is a catalyst.
• Each step is reversible.
O
CH3
C OH
CH3
+ H O CH2CH2CHCH3
+
H
O
CH3
CH3C OCH2CH2CHCH3
+ HOH
=>
Chapter 11
18
CH3CH2CH2
Br
Tosylate Esters
H
C O
H
H H
• Alcohol + p-Toluenesulfonic acid, TsOH
• Acid chloride is actually used, TsCl
O
CH3CH2
O H
+
HO
S
CH3
O
O
CH3CH2
O
S
O
Chapter 11
CH3 =>
+ HOH
19
CH3CH2CH2
Br
Sulfate Esters
H
C O
H
H H
Alcohol + Sulfuric Acid
O
HO
S OH
O
+
H
+ H O CH2CH3
O
S OCH2CH3
O
O
CH3CH2O H + HO
HO
S
O
+
OCH2CH3
O
Chapter 11
H
CH3CH2O
S
OCH2CH3
O
=>
20
CH3CH2CH2
Br
Nitrate Esters
O
O
+
N OH
+
H O CH2CH3
H
O
H
C O
H
H H
N OCH2CH3
O
CH2
O H
CH2
O H
CH2
O H
+
3 HO NO2
CH2
O NO2
CH2
O NO2
CH2
O NO2
nit roglycerine =>
glycerine
Chapter 11
21
CH3CH2CH2
Br
Phosphate Esters
O
HO
P
OH
O
OH
CH3OH
CH3O
P
OH
CH3OH
H
C O
H
H H
O
CH3O
P
OCH3
OH
OH
CH3OH
O
CH3O
P
OCH3
OCH3
Chapter 11
=>
22
CH3CH2CH2
Phosphate Esters in DNA
O CH2
Br
H
C O
H
H H
base
O
H
H
H
O
O
CH2
O
H
P
O
base
O
H
H
O
O
CH2
O
H
P
O
base
O
H
H
O
O
CH2
O
H
P
O
base
O
H
H
O
O
P
O
Chapter 11
O
=>
23
CH3CH2CH2
Br
Alkoxide Ions
H
C O
H
H H
• ROH + Na (or NaH) yields sodium alkoxide
• RO- + 1° alkyl halide yields ether (Williamson
ether synthesis)
CH3
CH3CH2CHCH3
+ CH3CH2
Br
O
CH2CH2CH O CH2CH3
=>
Chapter 11
24
POWER POINT IMAGES FROM
“ORGANIC CHEMISTRY, 5TH EDITION”
L.G. WADE
ALL MATERIALS USED WITH PERMISSION OF AUTHOR
CH3CH2CH2
Br
H
C O
H
H H
PRESENTATION ADAPTED FOR BURLINGTON COUNTY COLLEGE
ORGANIC CHEMISTRY COURSE
BY:
ANNALICIA POEHLER STEFANIE LAYMAN
CALY MARTIN
Chapter 11
25