text: The Cornforth reagent is a strong oxidizing agent which can convert primary alcohols to aldehydes and secondary alcohols to ketones, both as a solution or suspension. This application was first mentioned in 1969, but fully developed only in 1979 by E. J. Corey and G. Schmidt. They mentioned that reaction of saturated primary alcohols with PDC, using dimethylformamide as solvent, results in oxidation to carboxylic acids rather than aldehydes. However, no oxidation to carboxylic acids occurs on allylic and benzylic primary alcohols.
  The oxidation is usually carried out at ambient conditions, in nearly neutral pH conditions, in dimethylformamide or dichloromethane or their mixture. The choice of solvent or their ratio affects the reaction rate; in particular, higher content of dimethylformamide results in stronger oxidation. The slow oxidation rate for some alcohols can be accelerated by the addition of molecular sieves, organic acids or acetic anhydride or of their combinations. The acceleration by molecular sieves works best when their pore diameter is about 0.3 nm, and it is apparently unrelated to their water absorption capability. Among organic acids, acetic acid, pyridinium trifluoroacetate or pyridinium tosylate can be added, the first one being most efficient and easiest to remove. The achieved acceleration is remarkable, but the reaction inevitably turns from neutral (pH) to acidic. Comparable acceleration is achieved with acetic anhydride, which is used in sugar and nucleoside chemistry. Reaction acceleration depends not only on the additives but also on their form, so all reagents are preferred dry and freshly prepared, and PDC and molecular sieves should be finely ground. The disadvantage of the accelerators is that they may simultaneously promote several oxidation routes thereby reducing the selectivity of the reaction.
  In its chemical structure and functions, the Cornforth reagent is closely related to other pyridinium salts of hexavalent chromium oxide, such as pyridinium chlorochromate [PyH][CrOCl] and to pyridine complexes such as the Collins reagent, CrO·2Py in dichloromethane and the Sarret reagent, CrO·2Py in pyridine.