6.3 Oxidation–Reduction Reactions

LEARNING GOALS

After   Chapter 6.3,    you will    be  able    to:

Recall  the oxidizing   agents  and mechanism   for reacting    an  aldehyde    with    oxidizing   agents

Identify    common  reducing    agents  used    on  aldehydes   and ketones

Predict the product of  a   reaction    combining   aldehydes   or  ketones with    reducing    agents

Aldehydes occupy the middle of the oxidation–reduction spectrum; they are more oxidized than
alcohols but less oxidized than carboxylic acids. Ketones, on the other hand, are as oxidized as
secondary carbons can get.

OXIDATION OF ALDEHYDES

When aldehydes are further oxidized, they form carboxylic acids. Any oxidizing agent stronger than
PCC can perform this reaction. Some examples include potassium permanganate (KMnO 4 ),
chromium trioxide (CrO 3 ), silver(I) oxide (Ag 2 O), and hydrogen peroxide (H 2 O 2 ). This is shown in
Figure 6.11.

Figure 6.11. Aldehyde   Oxidation

Most    oxidizing   agents  will    turn    aldehydes   into    carboxylic  acids;  PCC,    however,    is  anhydrous   and is

not strong  enough  to  oxidize past    the point   of  an  aldehyde.