amines, and bicyclic tertiary amines in particular, accelerate the rate of osmium tetroxide
dihydroxylation of olefins by co-ordination to the metal.6The ligand systems shown above are the
result of many years of experimentation by the Sharpless group and others. Note that, since natural
alkaloids are only available in one enantiomeric form, the ligands which give rise to opposite
enantiomers in the dihydroxylation are derived from two different alkaloids. The ligands are thus
not enantiomers of each other, but are termed 'pseudoenantiomeric' by Sharpless.
In this experiment, you will be using the commercial AD-mix - a powder containing an osmium
source (K2OsO2(OH)4), the chiral ligand ([DHQ]2PHAL for AD-mix α, [DHQD]2PHAL for AD-
mix β), a co-oxidant for regeneration of osmium (VIII) (K3Fe(CN)6and a pH buffer (K2CO3) - to
perform the dihydroxylation of one of several olefins.
AD-MIXES contain approx. the following chemicals per 4.2g loading (as used here):
Potassium osmate: 4.4mg
(DHQ)2PHAL or (DHQD)2PHAL: 23mg
Potassium ferricyanide: 2.94g
Potassium carbonate: 1.24g
TOXIC
SEVERE IRRITANT TO EYES AND RESPIRATORY SYSTEM
system. If ingested can cause abdominal pain and vomiting, and irritation of the
respiratory system with coughing. Eye contact results in severe pain, blurred vision and
possible blindness.
Incompatible with strong oxidising materials.
Gives off toxic fumes in fire.
Absorb onto inert material and package in containers for disposal.
Fire hazards:
Spillage & disposal:
HARMFUL BY INGESTION
Hazardous reactions:
No known hazards, although solutions should NOT be treated with acid to avoid
generation of hydrogen cyanide.
MAY EVOLVE TOXIC FUMES IN FIRE. Flash point 76ºC, ignition temp.not
available; extinguish fire with dry powder.
Mop up with plenty of water and run to waste, diluting with copious water. For larger
spillages, transfer to container for disposal.