Illustrated Glossary of Organic Chemistry

Oxidation: (1) Any process in which there is an increase in the number of covalent bonds between an atom and atom(s) that are more electronegative. Commonly seen as, but not limited to, increasing the number of bonds between carbon and oxygen.

Combustion of methane is an oxidation because there is an increase (from zero to four) in number of bonds between carbon (EN = 2.5) and oxygen (EN = 3.5).


Free radical halogenation of methane is an oxidation because there is an increase (from zero to one) in the number of bonds between carbon (EN = 2.5) and bromine (EN = 2.8).


Reaction of sodium borohydride with acetone is a reduction because there is an increase (from zero to one) in the number of bonds between carbon (EN = 2.5) and hydrogen (EN = 2.1), and also between oxygen (EN = 3.5) and hydrogen (EN = 2.1).


Catalytic hydrogenation of propene is a reduction because there is an increase (from three to five) in the number of bonds between carbon (EN = 2.5) and hydrogen (EN = 2.1).

(2) Any process in which formal charge is made more positive by removing electrons.

Rusting of iron is an oxidation because of the formal charge change: Fe⁰ becomes Fe³⁺.