We have covered several oxidants that use a multi-valent atom (Cr, Cl, S, or I) as their active species, going from a higher oxidation state before the oxidation to a lower oxidation state after oxidizing the alcohol. Draw the structure of the following atoms, before and after the oxidation of an alcohol to a ketone or aldehyde. How many bonds to oxygen does each atom have before and after the oxidation? (a) the Cr in chromic acid
(b) the Cl in sodium hypochlorite
(c) the S in the Swern oxidation
(d) the I in the DMP reagent
(e) the carbinol C in the alcohol that is oxidized
Solution 3P
(a)
First, consider the chromium in chromic acid.
Chromium begins with four oxygen substituents and, after the oxidation, has only three oxygen substituents.
(b)
Secondly, consider the chlorine in sodium hypochlorite.
The chlorine atom starts with one oxygen bound to it and, after the oxidation, has no oxygen substituents.
(c)
Thirdly, consider the sulfur atom from the Swern oxidation. This oxidation uses dimethyl sulfoxide and forms dimethyl sulfide as a by-product.
The sulfur starts with one oxygen substituent and the product has no oxygens.
(d)
Consider the iodine atom in the DMP reagent. This reagent is used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones.
The iodine atom begins the reaction with four bonds to oxygen and after the oxidation, it has only two bonds to oxygen atoms.
(e)
Finally, consider the carbon atom in the carbinols that are oxidized.
The carbon atom begins with one bond to oxygen. It ends up with two bonds to oxygen (and one less bond to hydrogen). This is one way of defining an organic oxidation, using a carbon-oxygen bond to replace a carbon-hydrogen bond.
