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METHODS FOR THE SYNTHESIS OF ALCOHOLS (to date)
OH
I
-
OH
1. BH3
OH
H+/H2O
OH
2. NaOH/H2O2
1. OsO4
2. H2O2
OH
OH
1. mCPBA
OH
2. H+/H2O
SYN
O
Aldehydes
OH
H
R
ANTI
H
R
O
Na
OH
Ketones
R
R
R
R
O
epoxides
OH
R
R
OH
ELECTROPHILIC AND NUCLEOPHIC CARBON
Methylmagnesium bromide
d-
H3 C
d+
Mg
Br
Methyl lithium
Methyl chloride
d-
d+
d+
H3 C
Li
H3C
d-
Cl
TYPICAL ELECTROPHILES
Methyl chloride
d+
H3C
d-
Cl
acetone
O dd+
Alcohols, carbonyl compounds and carboxylic acids:
REDUCTION
Reduction: Addition of H2 (or H-), loss of O or O2 ; loss of X2
H
H
R
C
R
H
C
OH
H
Primary alcohol
H
O
NaBH4
R C
or
H
Raney Ni/
H2
Aldehyde
O
LiAlH4
R
C
OH
Carboxylic acid
must convert OH to
leaving group
H
H
R
C
H
R
C
OH
R'
Secondary alcohol
R'
must convert OH to
leaving group
R
C
R'
H
R
or
Raney Ni/
H2
R
C
R'
Ketone
H
Li H Al H
R"
R"
O
NaBH4
C
OH
R'
Tertiary alcohol
H
Lithium aluminium
hydride
Na
H
H B
H
H
Sodium borohydride
Comparison of
Reducing Agents
• LiAlH4 is stronger.
• LiAlH4 reduces more
stable compounds
which are resistant to
reduction.
=>
Alcohols, carbonyl compounds and carboxylic acids:
OXIDATION
Oxidation: loss of H2 , addition of O or O2, addition of X2 (halogens)
H
H
R
C
H
R
H
H
C
R
OH
H
R
C
OH
R
H2 SO4
C
OH
Carboxylic acid
O
R
C
H2 SO4
R'
Secondary alcohol
R'
C
Aldehyde
Na2Cr2O7 /
O
Na2Cr2O7 /
H
H
Primary alcohol
H
R
C
O
PCC
X
R'
Ketone
PCC
R"
R"
R
C
R'
H
R
C
OH
R'
Tertiary alcohol
X
NH CrO3Cl-