This document presents information about osmium tetroxide (OsO4). It discusses the chemical structure and synthesis of OsO4, noting that it forms slowly when osmium powder reacts with oxygen at room temperature. The document also covers the physical properties of OsO4, such as its solubility in organic solvents and water, melting point, and boiling point. Finally, the main application discussed is OsO4's use in the oxidation of alkenes to form glycols through syn addition, with examples given of the Upjohn dihydroxylation, Sharpless asymmetric dihydroxylation, and use of OsO4 in antitumor drug synthesis.

1. Presented By
Shubham Sharma
M .Pharm (1sem)
(Pharmaceutical Chemistry)
Roll No-20029
Presented To
Dr. Ashok Kumar Yadav
UGC Assistant Professor
UIPS, Panjab University

2. CONTENTS
 CHEMICAL STRUCTURE AND SYNTHESIS
 INTRODUCTION
 PHYSICAL PROPERTIES
 APPLICATIONS WITH THEIR MECHANISM

3. CHEMICAL FORMULA
OsO4 (OSMIUM TEROXIDE)
(TETRAHEDRAL)

4. SYNTHESIS
 OsO4 is formed slowly when osmium powder reacts with oxygen at ambient room
temperature. Reaction of bulk solid requires heating to 400○C.
 The toxic and volatile OsO4 can also be prepared in situ by the oxidation of
K2OsO2(OH)4 with NMO. NMO is also the cooxidant that enables the use of
a catalytic amount of OsO4, because this reagent is able to reoxidize an
Os(VI) species to an Os(VIII) species.

5. INTRODUCTION
1. The compound is noteworthy for its many uses, despite its toxicity
and the rarity of osmium.
2. It also has a number of interesting properties, one being that the
solid is volatile.
3. The compound is colourless, but most samples appear yellow.
This is most likely due to the presence of the impurity OsO2,
which is yellow –brown in colour.
4. Osmium oxide(Ⅷ) forms monoclinic crystals. It has a
characteristic acrid chlorine –like odour. The element name
osmium is derived from osme, Greek for odour.

6. PHYSICAL PROPERTIES
1. It is soluble in wide range of organic solvents . It is also moderately soluble in
water, with which it reacts reversibly to osmic acid.
2. Pure Osmium oxide(Ⅷ) is probably colourless and it has been suggested that its
yellow colour is due to osmium dioxide (OsO2) impurities.
3. The osmium tetroxide molecule is tertrahedral and therefore non-polar.
4. Melting Point = 40○C
5. Sublimes At Room Temperature
6. Boiling Point = 130○C
7. Solubility In Water = 6.2g/100ml
8. Solublilty In CCL4 = 375g/100ml

7. /NMO
NMO will again oxidize
this osmium to its +8
oxidation state , will see
it in upjohn
dihydroxylation

8. APPLICATIONS OF OSMIUM TETROXIDE
1) OXIDATION OF ALKENES (SYN DIHYDROXYLATION)
Osmium tetroxide oxidizes alkenes to give glycols through syn addition. When an
alkene reacts with osmium tetroxide, stereocenters can form in the glycol product. Cis
alkenes give meso products and trans alkenes give racemic mixtures.

9. CONTINUED….
OSMATE ESTER
H2S can also be used

10.  Dihydroxylation of alkenes can also be performed with cold, dilute potassium
permanganate (KMnO4). One advantage of OsO4 is that it is much more compatible
with other functional groups than KMnO4, which is kind of a ravenous beast.
Chemical Highlight
 Antitumor drugs have been formed by using dihydroxylation. This method
has been applied to the enantioselective synthesis of ovalicin, which is a
class of fungal-derived products called antiangiogenesis agents. These
antitumor products can cut off the blood supply to solid tumors. A
derivative of ovalicin, TNP-470, is chemically stable, nontoxic, and
noninflammatory. TNP-470 has been used in research to determine its
effectiveness in treating cancer of the breast, brain, cervix, liver, and
prostate.
 This reaction (Syn Dihroxylation) has been made both catalytic(Upjohn
dihydroxylation and asymmetric (sharpless asymmetric dihydroxylation).
CONTINUED

11. UPJOHN DIHYDROXYLATION

12. MECHANISM

13. The Sharpless Dihydroxylation or Bishydroxylation is used in the enantioselective
preparation of 1,2-diols from prochiral olefins. This procedure is performed with
an osmium catalyst and a stoichiometric oxidant [e.g. K3Fe(CN)6 or N-
methylmorpholine oxide (NMO)]; it is carried out in a buffered solution to ensure a
stable pH, since the reaction proceeds more rapidly under slightly basic conditions.
Enantioselectivity is achieved through the addition of enantiomerically-enriched
chiral ligands [(DHQD)2PHAL(β), (DHQ)2PHAL(α) or their derivatives]. These
reagents are also available as stable, prepackaged mixtures (AD-mix α and AD-mix
β, AD = asymmetric dihydroxylation) for either enantiopreference.
SHARPLESS ASYMMETRIC DIHROXYLATION

14. MECHANISM

15. LEMEIUX-JOHNSON REARRANGMENT

16. SYNTHESIS OF ISOSTEVIOL

17. THANK YOU