Advices For Studying Organic Chemistry

A Mechanism for the Reaction

Chromate Oxidations: Formation of the Chromate Ester
Step 1

C

O

H 3 C H

H 3 C

+ Cr O −

O

O

H O

Cr O −

OO

O

H OH H

H

C

O

H 3 C H

H 3 C

H

H

O

H

H

+

H

+

H OH

H

+

The alcohol donates an electron pair to the

chromium atom, as an oxygen accepts a proton.

One oxygen loses a proton;

another oxygen accepts a proton.

C

O

H 3 C H

H 3 C Cr O −

OO

O

H

+

Cr O

O

O O

H H

H C

O

H 3 C H

H 3 C

+ H

H

A molecule of water departs as a leaving group

as a chromium-oxygen double bond forms.

Chromate ester

A Mechanism for the Reaction

Chromate Oxidations: The Oxidation Step
Step 2

O

H

H

C

O

H 3 C H

H 3 C Cr O

O

O

H

O

O

H

CO

H 3 C

H 3 C

Cr O H OH

H

+++

The chromium atom departs with a pair of electrons that formerly belonged to the

alcohol; the alcohol is thereby oxidized and the chromium reduced.