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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 #7: Oxidation of Secondary Alcohols to Ketones H2CrO4 (Jone's Reagent)
or
1) KMnO4 / NaOH , acetone
OH
2) Acid workup
either or both
or
enantiomers
PCC / CH2Cl2
Mechanism for Jone’s Reagent H2O
H
O
HO
O
HO
Cr
O
O
O
O
Cr
O
O
H
H
CH 3
HO
O
Cr
OH
CH 3
O
HO
O
OH
H
H
H
O
H
O
Cr
HO
HCrO3-
O
O
O
Cr
O
H 3C
OH2
O
O
HO
CH
H
H2O
Ketone
a chromate ester
Although chromic acid and permanganate are powerful oxidizing agents the reaction only requires a two-­‐electron transfer to transform a 2° alcohol to a ketone. The same results will be obtained by the use of the PCC reagent although under milder conditions. A similar mechanism for the permanganate occurs except that the media is basic. H
O
O
O
HO
O
Mn
O
Mn
O
O
O
O
CH 3
HMnO4- + H2O
OH
O
O
Mn
O
O
H 3C
O
H
3
HO
ketone