Transcript alcohols-II-12-ques

Alcohol Reactions
Alcohol Reactions
Conversions to esters (Acetate Lab)
Reactions with hydrogen halides
Acid-catalyzed hydrations
Esterification
Esterification
O
ROH +
O
H+
R'COR +
R'COH
condensation
Fischer esterification
acid catalyzed
reversible
H2O
Example of Fischer Esterification
O
COH + CH3OH
0.1 mol
0.6 mol
H2SO4
O
COCH3 +
H2O
70% yield based on benzoic acid
Reaction of Alcohols with Acyl Chlorides
O
ROH +
R'CCl
O
R'COR +
High yields
Not reversible when carried out
in presence of pyridine.
HCl
Example
CH3CH2
O
OH
+
O2N
CCl
CH3
pyridine
CH3CH2
O
NO2
OC
CH3
(63%)
Reaction of Alcohols with Acid Anhydrides
O O
ROH + R'COCR'
O
R'COR +
analogous to acyl chlorides
O
R'COH
Example
O O
C6H5CH2CH2OH + F3CCOCCF3
pyridine
O
C6H5CH2CH2OCCF3
(83%)
Reactions of Alcohols
“Poor”
Reactions of Alcohols
Oxidation
Conversion to ethers
Oxidation of Alcohols
Oxidation of Alcohols
Primary alcohols
O
O
RCH2OH
RCH
RCOH
Secondary alcohols
OH
O
RCHR'
RCR'
from H2O
Strong Oxidizing Agents
In aqueous solution:
Mn(VII)
Cr(VI)
KMnO4 CrO3/ H2SO4 = H2CrO4
K2Cr2O7 / H2SO4 = H2Cr2O7
Oxidize 1o alcohols to
carboxylic acids.
Cannot stop at aldehydes.
Aqueous Cr(VI)
H
FCH2CH2CH2CH2OH
OH
K2Cr2O7
H2SO4
H2O
Na2Cr2O7
H2SO4
H2O
O
O
FCH2CH2CH2COH
(74%)
(85%)
Question
• Treatment of 1-propanol with K2Cr2O7,
H2SO4, and heat will produce:
•
A)
•
C)
B)
D)
Question
What is the product of the following reaction?
OH
H2CrO4, acetone 35o C
OH
A.
C.
O
O
O
OH
B.
O
O
H
O
OH
D.
O
Specialized Oxidizing Agents
[Nonaqueous Sources of Cr(VI)]
Used in CH2Cl2
Pyridinium dichromate (PDC)
(C5H5NH+)2 Cr2O72–
Pyridinium chlorochromate (PCC)
C5H5NH+ ClCrO3–
“Collins Reagent”
Jones Reagent:
CrO3/ H2SO4
acetone
(does not affect
Carbon=Carbon
double bonds;
oxidizes 2o
alcohols to
ketones)
Example: Oxidation of
a Primary Alcohol with PCC
ClCrO3–
+N
H
PCC
CH3(CH2)5CH2OH
O
CH3(CH2)5CH
CH2Cl2
(78%)
Question
• What is the product of the reaction of 1butanol with PCC in CH2Cl2?
•
A)
B)
•
C)
D)
Question
What is the product of the following reaction?
OH
xs PCC, CH2Cl2, 25o C
OH
A.
C.
O
O
O
OH
B.
O
O
H
O
OH
D.
O
Example: Oxidation of
a Primary Alcohol with PDC
(CH3)3C
CH2OH
PDC
CH2Cl2
O
(CH3)3C
CH
(94%)
Question
•
•
•
•
•
For the following reaction, select the statement that
best describes it.
RCH2OH + PDC [(C5H5NH+)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.
Conversion of Alcohols to Ethers
Conversion of Alcohols to Ethers
RCH2O
CH2R
H
OH
H+
RCH2O
CH2R
+
H
OH
Acid-catalyzed
Referred to as a "condensation"
Equilibrium; most favorable for primary alcohols
Example
2CH3CH2CH2CH2OH
H2SO4, 130°C
CH3CH2CH2CH2OCH2CH2CH2CH3
(60%)
Intramolecular Analogue
HOCH2CH2CH2CH2CH2OH
via:
H2SO4
130°
••
•• O
O
(76%)
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:
•
A)
propanal
B)
propanoic acid
•
C)
propanol
D)
methyl propanoate
Question
Classify the following as oxidation, reduction or neither oxidation or
reduction
I. Oxidation
II. Reduction
III. Neither oxidation or
reduction
A.
B.
C.
D.
E.
I: a, c, d; II: e, f; III: b
I: a, d, e; II: c, f; III: b
I: c, d, e; II: a, f; III: b
I: c, f; II: a, d, e; III: b
I: c, e;II: a, d, f; III: b