In organic reactions, adding an oxygen is considered __ and removing an oxygen is considered __.

In organic chemistry, the addition and removal of oxygen atoms in a molecule are closely associated with the concepts of oxidation and reduction. Specifically, adding an oxygen atom to a substrate generally leads to oxidation. This is because oxidation can be defined as an increase in the oxidation state of a molecule, which often occurs when oxygen is added.

Conversely, the removal of an oxygen atom from a molecule corresponds to reduction. Reduction involves a decrease in oxidation state, which typically occurs when oxygen is removed, as fewer bonds to oxygen lower the electron density around the central atom, reducing its oxidation state.

Thus, the understanding of oxidation as the addition of oxygen and reduction as the removal of oxygen is key in organic chemistry reactions, making the connection between these processes essential for grasping larger concepts of redox chemistry.