Alccois-2

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Chapter 11 1
CH3CH2CH2
C
HH
Br O
H
H
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 2
CH3CH2CH2
C
HH
Br O
H
H
Summary Table
=>
Chapter 11 3
CH3CH2CH2
C
HH
Br O
H
H
Oxidation States
• Easy for inorganic salts
CrO42- reduced to Cr2O3
KMnO4 reduced to MnO2
• Oxidation: loss of H2, gain of O, O2, or X2
• Reduction: gain of H2 or H-, loss of O, O2, 
or X2 
• Neither: gain or loss of H+, H2O, HX
=>
Chapter 11 4
CH3CH2CH2
C
HH
Br O
H
H1º, 2º, 3º Carbons
=>
Chapter 11 5
CH3CH2CH2
C
HH
Br O
H
H
Oxidation of 2° Alcohols
• 2° alcohol becomes a ketone
• Reagent is Na2Cr2O7/H2SO4
• Active reagent probably H2CrO4
• Color change: orange to greenish-blue
CH3CHCH2CH3
OH
Na2Cr2O7 / H2SO4
CH3CCH2CH3
O
=>
Chapter 11 6
CH3CH2CH2
C
HH
Br O
H
HOxidation of 1° Alcohols
• 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.
CH3CH2CH2CH2
OH N H CrO3Cl
CH3CH2CH2CH
O
=>
Chapter 11 7
CH3CH2CH2
C
HH
Br O
H
H3° Alcohols Don’t Oxidize
• Cannot lose 2 H’s
• Basis for chromic acid test
=>
Chapter 11 8
CH3CH2CH2
C
HH
Br O
H
H
Other Oxidation Reagents
• Collins reagent: Cr2O3 in pyridine
• Jones reagent: chromic acid in acetone
• KMnO4 (strong oxidizer)
• Nitric acid (strong oxidizer)
• CuO, 300°C (industrial dehydrogenation)
• Swern oxidation: dimethylsulfoxide, with 
oxalyl chloride and hindered base, 
oxidizes 2 alcohols to ketones and 1
alcohols to aldehydes. =>
Chapter 11 9
CH3CH2CH2
C
HH
Br O
H
H
Biological Oxidation
• Catalyzed by ADH, alcohol dehydrogenase.
• Oxidizing agent is NAD+, nicotinamide
adenine dinucleotide.
• Ethanol oxidizes to acetaldehyde, then acetic 
acid, a normal metabolite.
• Methanol oxidizes to formaldehyde, then 
formic acid, more toxic than methanol.
• Ethylene glycol oxidizes to oxalic acid, toxic.
• Treatment for poisoning is excess ethanol.
=>
Chapter 11 10
CH3CH2CH2
C
HH
Br O
H
H
Alcohol as a Nucleophile
• ROH is weak nucleophile
• RO- is strong nucleophile
• New O-C bond forms, O-H bond breaks.
=>
C
O
H
R X
Chapter 11 11
CH3CH2CH2
C
HH
Br O
H
HAlcohol 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)
=>
C
O
H
 +
C-Nuc bond forms, 
C-O bond breaks
Chapter 11 12
CH3CH2CH2
C
HH
Br O
H
H
Formation of Tosylate Ester
p-toluenesulfonyl chloride
TsCl, “tosyl chloride”
C
O
H
CH3
S
Cl
OO N
CH3
S OO
OH
C
CH3
S
O
OO
C
ROTs,
a tosylate ester 
=>
Chapter 11 13
CH3CH2CH2
C
HH
Br O
H
H
SN2 Reactions of Tosylates
• 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 14
CH3CH2CH2
C
HH
Br O
H
HSummary of Tosylate 
Reactions
=>
Chapter 11 15
CH3CH2CH2
C
HH
Br O
H
HReduction of Alcohols
• Dehydrate with conc. H2SO4, then add H2
• Tosylate, then reduce with LiAlH4
CH3CHCH3
OH
H2SO4
CH2 CHCH3
H2
Pt
CH3CH2CH3
alcohol alkene alkane
alcohol
CH3CHCH3
OH
TsCl
CH3CHCH3
OTs
LiAlH4
alkane
CH3CH2CH3
tosylate
=>
Chapter 11 16
CH3CH2CH2
C
HH
Br O
H
HReaction with HBr
• -OH of alcohol is protonated
• -OH2+ is good leaving group
• 3° and 2° alcohols react with Br- via SN1
• 1° alcohols react via SN2
H3O
+ Br-
R O H R O H
H
R Br =>
Chapter 11 17
CH3CH2CH2
C
HH
Br O
H
HReaction with HCl
• Chloride is a weaker nucleophile than 
bromide.
• Add ZnCl2, which bonds strongly with
-OH, to promote the reaction.
• The chloride product is insoluble.
• Lucas test: ZnCl2 in conc. HCl
1° alcohols react slowly or not at all.
2 alcohols react in 1-5 minutes.
3 alcohols react in less than 1 minute.
=>
Chapter 11 18
CH3CH2CH2
C
HH
Br O
H
H
Limitations of HX Reactions
• HI does not react
• Poor yields of 1° and 2° chlorides
• May get alkene instead of alkyl halide
• Carbocation intermediate may 
rearrange. 
=>
Chapter 11 19
CH3CH2CH2
C
HH
Br O
H
HReactions with 
Phosphorus Halides
• Good yields with 1° and 2° alcohols
• PCl3 for alkyl chloride (but SOCl2 better)
• PBr3 for alkyl bromide
• P and I2 for alkyl iodide (PI3 not stable) 
=>
Chapter 11 20
CH3CH2CH2
C
HH
Br O
H
HMechanism with PBr3
• P bonds to -OH as Br- leaves
• Br- attacks backside (SN2)
• HOPBr2 leaves =>
Chapter 11 21
CH3CH2CH2
C
HH
Br O
H
H
Reaction with 
Thionyl Chloride
• 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 22
CH3CH2CH2
C
HH
Br O
H
H
Dehydration Reactions
• Conc. H2SO4 produces alkene
• Carbocation intermediate
• Saytzeff product
• Bimolecular dehydration produces ether
• Low temp, 140°C and below, favors ether
• High temp, 180°C and above, favors 
alkene =>
Chapter 11 23
CH3CH2CH2
C
HH
Br O
H
H
Dehydration Mechanisms
CH3CHCH3
OH
H2SO4
alcohol
CH3CHCH3
OH
H
CH3CHCH3
CH2 CHCH3
H2O
CH3OH
H3O
+
CH3OH CH3 OH2 CH3 O
H
CH3
H2O
CH3OCH3
=>
Chapter 11 24
CH3CH2CH2
C
HH
Br O
H
HEnergy Diagram, E1
=>
Chapter 11 25
CH3CH2CH2
C
HH
Br O
H
H
Unique Reactions of Diols
• Pinacol rearrangement
• Periodic acid cleavage 
=>
Chapter 11 26
CH3CH2CH2
C
HH
Br O
H
HPinacol Rearrangement
• Pinacol: 2,3-dimethyl-2,3-butanediol
• Dehydration with sulfuric acid
CH3 C
CH3
OH OH
CH3
C CH3
H+ CH3 C
CH3
OH OH
CH3
C CH3
H
CH3 C
CH3
OH
C
CH3
CH3
CH3 C
CH3
OH
C
CH3
CH3
CH3 C
OH
CH3
C CH3
CH3
CH3 C
OH
CH3
C CH3
CH3
CH3 C
O
CH3
C CH3
CH3
pinacolone
=>
Chapter 11 27
CH3CH2CH2
C
HH
Br O
H
HPeriodic Cleavage 
of Glycols
Same products formed as from ozonolysis
of the corresponding alkene.
CH3 C
H
OH OH
CH3
C CH3
HIO4
CH3 C
H
O
+ C
O
CH3
CH3
C C
H3C
H CH3
CH3
OsO4
H2O2
O3
(CH3)2S
=>
Chapter 11 28
CH3CH2CH2
C
HH
Br O
H
H
Esterification
• Fischer: alcohol + carboxylic acid
• Tosylate esters
• Sulfate esters
• Nitrate esters
• Phosphate esters
=>
Chapter 11 29
CH3CH2CH2
C
HH
Br O
H
H
Fischer Esterification
• Acid + Alcohol yields Ester + Water
• Sulfuric acid is a catalyst.
• Each step is reversible.
CH3 C OH
O
+ CH2CH2CHCH3
CH3
OH
H+
CH3C
O
OCH2CH2CHCH3
CH3
+ HOH
=>
Chapter 11 30
CH3CH2CH2
C
HH
Br O
H
H
Tosylate Esters
• Alcohol + p-Toluenesulfonic acid, TsOH
• Acid chloride is actually used, TsCl
CH3CH2 O H + HO S
O
O
CH3
CH3CH2 O S
O
O
CH3
HOH+
=>
Chapter 11 31
CH3CH2CH2
C
HH
Br O
H
H
Sulfate Esters
Alcohol + Sulfuric Acid
+HO S
O
O
OH H O CH2CH3
H+
OCH2CH3
O
O
SHO
CH3CH2O H + OCH2CH3
O
O
SHO
H+
CH3CH2O S
O
O
OCH2CH3
=>
Chapter 11 32
CH3CH2CH2
C
HH
Br O
H
H
Nitrate Esters
+ H O CH2CH3
H+
N OH
O
O
OCH2CH3N
O
O
CH2
CH2
CH2
O H
O H
O H
+ 3 HO NO2
CH2
CH2
CH2
O NO2
O NO2
O NO2
nitroglycerineglycerine =>
Chapter 11 33
CH3CH2CH2
C
HH
Br O
H
H
Phosphate Esters
P
O
OH
OH
HO CH3OH P
O
OH
OH
CH3O
CH3OH
P
O
OCH3
OH
CH3O
P
O
OCH3
OCH3
CH3O
CH3OH
=>
Chapter 11 34
CH3CH2CH2
C
HH
Br O
H
HPhosphate Esters in DNA
=>
OCH2
H
H
H
base
O
P
O
O O
OCH2
H
H
H
base
O
P
O
O O
OCH2
H
H
H
base
O
P
O
O O
O
OCH2
H
H
H
base
O
P
O
O O
Chapter 11 35
CH3CH2CH2
C
HH
Br O
H
H
Alkoxide Ions
• ROH + Na (or NaH) yields sodium alkoxide
• RO- + 1° alkyl halide yields ether (Williamson 
ether synthesis)
CH3CH2CHCH3
O
CH3CH2 Br+ CH2CH2CH
CH3
O CH2CH3
=>