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Chem 343 – Organic Reactions Chapter 10 Prepared by José Laboy, MS http: www.chem.wisc.edu/areas /clc (Resource page) Reactions of Alcohols #6: Oxidation of Primary Alcohols to Carboxylic Acids OH
H2CrO4 (Jone's Reagent)
or
1) KMnO4 / NaOH , acetone
2) Acid workup
Mechanism for Jone’s Reagent H2O
H
OH
O
O
O
HO
OH
Cr
O
O
O
Cr
O
H
Cr
HO
H
O
O
O
OH
HO
O
OH
H
H
H
O
H
O
O
Cr
HO
O
OH2
HCrO3-
O
O
H
Cr
H
O
O
O
H
HO
H
aldehyde
H2O
a chromate ester
O
OH
O
O
H2O
H
HO
OH
H
H
H2O
Cr
O
O
H
OH
H
O
a gem diol
H
H2O
H
O
O
Cr
HO
OH
Cr
O
OH
OH
H
H
O
a carboxylic acid
O
O
Cr
O
OH
O
HCrO3-
HO
H
OH
O
O
O
O
OH
HO
O
Cr
O
OH2
H
H2O
OH HO
Chromic acid and permanganate are powerful oxidizing agents. The reaction will not stop at the aldehyde. The overall reaction requires a 4 electron transfer. A similar mechanism for the permanganate occurs except that the media is basic. The major product is a carboxylate, which is transformed into a carboxylic acid by acid workup. HMnO4- + H2O
H
O
OH
O
O
OH
Mn
O
O
O
Mn
O
O
O
Mn
O
O
O
H
O
HO
HO
H
O
HMnO4- + H2O
O
OH
O
O
O
O
Mn
Mn
O
OH
O
O
OH
O
O
O
O
Mn
HO
H
O
O
O
H
OH
H2O
O
O
acid workup
O
OH
a carboxylic acid
a carboxylate
O
OH