Paper, cloth, and many other products are bleached to a lighter color with chlorine or oxygen.

Many organic materials contain small amounts of compounds with conjugated double bonds. Although many organic compounds are colorless, absorbing light in the ultraviolet region, some of these conjugated compounds absorb light in the visible region. These conjugated compounds have delocalized molecular orbitals available which are close to one another in energy so the transitions between levels are in the visible region. These double bonds are also reactive and easily oxidized. Chlorine and other oxidizing agents oxidize these bonds leaving colorless compounds behind and producing a whiter product.