oxidizing agent
Summary
An oxidizing agent is the species that takes electrons from another species, so it is itself reduced. In organic chemistry, it converts alcohols to carbonyl compounds or acids. Testable point: the oxidant is the one reduced, and its strength decides where oxidation stops.
Detail
Meaning: An oxidizing agent (oxidant) causes another species to lose electrons, and it gains those electrons, so its own oxidation state falls. In organic chemistry, a carbon is oxidized when it gains bonds to oxygen or loses bonds to hydrogen. Common oxidants are PCC, CrO₃ with H₂SO₄ (Jones reagent), Na₂Cr₂O₇, and KMnO₄. In biochemistry the same idea applies: NAD⁺ is the oxidizing agent when it accepts electrons from a substrate and becomes NADH.
On the MCAT: Expect a reaction scheme asking for the product. PCC oxidizes a primary alcohol to an aldehyde and a secondary alcohol to a ketone. Stronger oxidants such as Jones reagent or KMnO₄ carry a primary alcohol on to a carboxylic acid. A tertiary alcohol has no hydrogen on the carbinol carbon, so it resists these oxidations. A passage may also say that orange Cr(VI) turns green as it becomes Cr(III), which shows the oxidant being reduced. Questions may ask you to rank the strength of oxidants or to pick the reagent that stops at the aldehyde.
Common confusion: Students call the alcohol the oxidizing agent because it is the molecule being oxidized. The oxidizing agent is the electron acceptor and is the species reduced. The alcohol is the reducing agent. Reagents like NaBH₄ and LiAlH₄ are reducing agents, since they donate hydride and are oxidized.
Sources
- Organic Chemistry (Wade)
- Organic Chemistry (Klein)
- Organic Chemistry (Clayden)
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.