In Chapter 15, we learned a number of redox reactions involving transformations of aldehydes, ketones, and alcohols. (See the chart of carbon oxidation states.)

Here are those transformations summarized with generic molecules; blue signifies a reduction, red an oxidation.

Here are those same reactions with specific R groups:

Notice that reductions in which hydrogens are added are reversible; those in which carbon groups are added are not.

Do remember that these charts do not specify all of the conditions for each reaction step; for example, Grignard additions actually involve two steps: addition, carried out in ether solution, and protonation, carried out by addition of water to the reaction mixture.