A number of oxidation reactions and the relevant oxidizing agents are shown in Figure 4.7. Note that
the goal at this point should not be memorization of these reactions, but recognition of two
themes: oxidation reactions tend to feature an increase in the number of bonds to oxygen, and
oxidizing agents often contain metals bonded to a large number of oxygen atoms.
Figure 4.7. Oxidation Reactions and Common Oxidizing AgentsREDUCING AGENTS AND REACTIONS
Conversely, reduction refers to a decrease in oxidation state. Reduction of a carbon occurs when a
bond between a carbon atom and an atom that is more electronegative than carbon is replaced by a
bond to an atom that is less electronegative than carbon. In practice, this usually means increasing
the number of bonds to hydrogen and decreasing the number of bonds to other carbons, nitrogen,
oxygen, or halides.
Good reducing agents include sodium, magnesium, aluminum, and zinc, which have low
electronegativities and ionization energies. Metal hydrides, such as NaH, CaH 2 , LiAlH 4 , and NaBH 4 ,
are also good reducing agents because they contain the H– ion.
Aldehydes and ketones will be reduced to primary and secondary alcohols, respectively. This
reaction is exergonic, but exceedingly slow without a catalyst. Amides can be reduced to amines