This document discusses oxidation reactions with osmium tetroxide (OsO4). It defines oxidation as the gain of oxygen, removal of hydrogen, or loss of electrons. OsO4 is described as a highly toxic volatile oxidizing agent with an oxidation state of +8 that is used to introduce hydroxyl groups into organic compounds through cis-hydroxylation of carbon-carbon double bonds. The mechanism involves the pi electrons of the alkene forming a 5-membered cyclic osmate ester intermediate. Hydroxide then liberates the cis-diol product while reducing the oxidation state of osmium from +8 to +6.

1. Organic Chemistry
Oxidation Reactions with
Osmium tetroxide
ANAM
FATIMA
ROLL NO 20
GC. Women University,
Sialkot

2. Oxidation
Definition
 Gain of oxygen.
 Removal of hydrogen.
 Lose of electrons.
 Functional group conversion from low oxidation state to higher oxidation
state . E.g. Fe+2 Fe+3+ e-

3. An oxidizing agent, or oxidant, is that oxidize the compounds
and is reduced itself in a chemical reaction. Oxidizing agent is
normally in one of its higher possible oxidation states because
it will gain electrons and be reduced.
Types of Reagents
 Metal base oxidants
Oxidizing agents:
Definition
Non-metals base oxidants

4. Metal base oxidation
 Chromium based oxidation
 Manganese based oxidation
 Titanium based oxidation
 Ruthenium based oxidation
 Osmium based oxidation
 Lead based oxidation
 Per acids Oxidation
 Photo oxidation
 Bio-oxidation
Non-metal base oxidation

5. Oxidation with Osmium tetroxide (OsO4).
• A highly toxic and volatile oxide of osmium used in industry as
an oxidizing agent. Its vapor can cause eye, skin, and lung
damage.
After oxidation the oxidation state of
OsO4 change from +8 to +6.
• It is a reagent, mostly used for the cis-hydroxylation of carbon-
carbon double bond.
• Hydroxylation is the process that introduces hydroxyl group in
organic compound.
Oxidation State +8

6. Examples
Example 3:

7. Step 1:
The pi- electrons in the alkene act as a
nucleophile forming a favorable 5 membered
ring as a cyclic osmate ester as an intermediate.
Step 2:
The hydroxide liberates the cis-diol and after
oxidation osmium changes oxidation State from
+8 to +6 this shows that OsO4 reduced.
Mechanism for the reaction of alkenes

8. Similarity between OsO4 and KMnO4
The mechanism dihydroxylation of alkenes by the both of them is same but one
advantage of OsO4 is that it is much more compatible with other functional
groups than KMnO4.
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