Preparation_of_the_Sarett_reagent Sarett_oxidation

1 preparation of sarett reagent

1.1 techniques
1.2 safety
1.3 collins technique

preparation of sarett reagent
techniques

the brick-red color of unreacted chromium trioxide (chromic anhydride).

the sarett reagent prepared in 1953 addition of chromic anhydride pyridine first, reagent grade pyridine must cooled 15–20 °c. then, small initial portion of chromic anhydride stirred pyridine. eventually, brick-red anhydride transform orange-yellow sarett reagent in exothermic reaction. @ point remaining anhydride may gradually stirred solution. must done mixture never rises above 30 °c. final product slurry of excess pyridine , precipitated sarett reagent, can take hour prepare (per 100 g yield). sarett oxidation carried out in mixture.

safety

improper handling of chromium trioxide can result in fire.

the specific methods of reagent s preparation critical, improper technique can cause explosion of materials. technical improvements original methodology have reduced risks associated preparation. 1 such recent improvement reduced likelihood of explosion using chromic anhydride granules sink below surface of cooled pyridine upon addition. should mentioned chromium trioxide corrosive carcinogen , therefore must handled extreme care.

collins technique

the original collins oxidation calls sarett reagent removed excess pyridine , dissolved in less basic methylene chloride. while new solvent improves overall yield of reaction, requires dangerous transfer of pyrophoric reagent. 1970 ratcliffe variation reduced risk of explosion calling sarett reagent made in situ. achieved creating sarett reagent according original protocol using stirred mixture of pyridine , methylene chloride.