Review of Reactions of Alcohols
Reaction with hydrogen halides
Reaction with thionyl chloride
Reactions of Alcohols:
Reaction with phosphorous trihalides
Review and New
Acid-catalyzed dehydration
Conversion to sulfonate esters
New Reactions of Alcohols
Oxidation
Conversion to ethers
Esterification
Oxidation of Alcohols
Oxidation of Alcohols
Primary alcohols
RCH2OH
Strong Oxidizing Agents
In aqueous solution:
O
O
RCH
RCOH
Mn(VII)
Cr(VI)
KMnO4
CrO 3/ H 2SO4 = H2CrO 4
K2Cr2O7 / H 2SO4 = H2Cr2O7
Secondary alcohols
OH
O
RCHR'
RCR'
from H2O
Oxidize 1o alcohols to
carboxylic acids.
Cannot stop at aldehydes.
aldehydes.
Aqueous Cr(VI)
Question
H
FCH2CH2CH2CH2OH
K2Cr2O7
OH
H2SO4
H 2O
Na2Cr2O7
H2SO4
H 2O
• Treatment of 1-propanol with K2Cr2O7,
H2SO4, and heat will produce:
•
A)
•
C)
B)
O
O
FCH2CH2CH2COH
(74%)
(85%)
Specialized Oxidizing Agents
[Nonaqueous Sources of Cr(VI)]
Question
Used in CH 2Cl2
Jones Reagent:
Pyridinium dichromate (PDC)
CrO 3/ H 2SO4
acetone
(C5H5NH+)2 Cr2O72–
Pyridinium chlorochromate (PCC)
“Collins Reagent”
Reagent”
Example: Oxidation of
a Primary Alcohol with PCC
A)
B)
•
C)
D)
Question
• What is the product of the reaction of 1butanol with PCC in CH2Cl2?
H
CH2Cl2
•
ClCrO3–
+N
PCC
• Treatment of 1-propanol with CrO3, H2SO4,
and acetone will produce:
(does not affect
Carbon=Carbon
double bonds)
C5H5NH+ ClCrO 3–
CH3(CH2)5CH2OH
D)
O
•
A)
B)
•
C)
D)
CH3(CH2)5CH
(78%)
Example: Oxidation of
a Primary Alcohol with PDC
Question
•
(CH3)3C
CH2OH
•
PDC
•
CH2Cl2
•
O
(CH3)3C
•
CH
For the following reaction, select the statement that
best describes it.
RCH 2OH + PDC [(C
(C5H 5NH +)2 Cr2O72–] →
A)
The alcohol is oxidized to an acid, and
the Cr(VI) is reduced.
B)
The alcohol is oxidized to an aldehyde,
and the Cr(VI) is reduced.
C)
The alcohol is reduced to an aldehyde,
and the Cr(III) is oxidized.
D)
The alcohol is oxidized to a ketone, and
the Cr(VI) is reduced.
(94%)
Conversion of Alcohols to Ethers
RCH2O
CH2R
H
OH
Conversion of Alcohols to Ethers
H+
RCH2O
CH2R
+
H
OH
Acid-catalyzed
Referred to as a "condensation"
Equilibrium; most favorable for primary alcohols
Example
Intramolecular Analogue
2CH3CH2CH2CH2OH
HOCH2CH2CH2CH2CH2OH
H2SO4
via:
130°
130°
H2SO4, 130°
130°C
••
CH3CH2CH2CH2OCH2CH2CH2CH3
(76%)
(60%)
•
•O
O
H
Reaction normally works well only for
5- and 6-membered rings.
H
O •• +
H
Question
• When 1-propanol is treated with
Na2Cr2O7/H2SO4 followed by treatment with
CH3OH, H2SO4 the product isolated is:
Esterification
•
A)
propanal B)
propanoic acid
•
C)
propanol D)
methyl propanoate
Example of Fischer Esterification
Esterification
O
O
ROH
ROH +
R'COR
R'COR +
R'COH
COH + CH3OH
O
H+
0.1 mol
H 2O
0.6 mol
H2SO4
condensation
Fischer esterification
O
acid catalyzed
COCH3 +
reversible
H 2O
70% yield based on benzoic acid
Reaction of Alcohols with Acyl Chlorides
Example
CH3CH2
O
ROH
ROH +
R'CCl
OH +
O
R'COR
R'COR +
O
HCl
O 2N
CCl
CH3
pyridine
High yields
Not reversible when carried out
in presence of pyridine.
CH3CH2
O
NO2
OC
CH3
(63%)
Reaction of Alcohols with Acid Anhydrides
Example
O O
O O
ROH
ROH + R'COCR'
O
R'COR
R'COR +
O
C6H5CH2CH2OH + F3CCOCCF3
R'COH
pyridine
analogous to acyl chlorides
O
C6H5CH2CH2OCCF3
(83%)