How does carbon gain or lose electron density in organic redox reactions?

In organic redox reactions, a carbon atom's electron density changes based on the electronegativity of the atoms to which it is bonded.12

Mechanisms of Electron Density Change

• Oxidation: A carbon atom becomes oxidized when it loses electron density. This typically occurs when carbon forms bonds with more electronegative atoms, such as oxygen, or when hydrogen atoms are removed from the carbon.1
• Reduction: A carbon atom becomes reduced when it gains electron density. This generally occurs when carbon bonds to less electronegative atoms or when hydrogen is added to the carbon atom.13

Conceptual Framework

These changes are formally understood through oxidation states, which are assigned by conceptually distributing shared electrons to the atom with the greater attraction for them. Because carbon has an electronegativity of 2.55, it gains electron density when bonded to elements with lower electronegativity values (like hydrogen at 2.2) and loses density when bonded to more electronegative elements (like oxygen at 3.44). Because an increase in electron density at one site must be balanced by a decrease elsewhere, oxidation and reduction always occur in tandem.21