Oxidation with chromium(VI) complexes: Difference between revisions

Revision as of 09:41, 25 April 2011

Revision as of 12:40, 20 June 2011

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Catalytic methods employing cheap, clean terminal oxidants in conjunction with catalytic amounts of chromium reagents produce only small amounts of metal byproducts.<ref>Muzart, J. ''Tetrahedron Lett.'', '''1987''', ''28'', 2133.</ref> However, undesired side reactions mediated by stoichiometric amounts of the terminal oxidant may occur.

==Experimental Conditionsconditions and Procedureprocedure==

===Typical Conditionsconditions===

Reagent-grade pyridine is usually sufficient for the preparation of PDC and PCC. Although these reagents may darken over time, their loss in activity is minimal.{{What}} Isolated reagents should be stored in a desiccator in the dark. Care should be taken when adding chromium trioxide to pyridine, as ignition of pyridine has been known to occur. Celite® or silica gel may be used to facilitate the removal of polymeric chromium byproducts from the reaction mixture; these adsorbents also serve as convenient buffer systems and dessicants[[desiccant]]s.

Reduced chromium residues can be removed from glassware with concentrated HCl or 10-1510–15% aqueous HF. Solid chromium waste should never be thrown away, as residual CrO₃ may ignite. Chromium(VI) reagents are toxic and should be handled with care in a well-ventilated fume hood.

==References==