Reactions Of Substituted: Quinones

Usually, the initial product is a hydroquinone. In the presence of excess quinone or air, this often oxidizes back into a new, substituted quinone. 2. Diels-Alder Cycloaddition Substituted quinones act as powerful dienophiles . Electronic Effects: Electron-withdrawing groups (like −CNnegative cap C cap N −CO2Rnegative cap C cap O sub 2 cap R

Substituted quinones are some of the most versatile electrophiles in organic chemistry. Because the quinone core is electron-deficient, their reactivity is largely governed by the nature and position of the substituents ( -groups) attached to the ring. 1. Nucleophilic Conjugate Addition (Michael Addition) reactions of substituted quinones

Large groups can hinder the approach of the diene, often dictating which face of the quinone is attacked. Usually, the initial product is a hydroquinone

) on the quinone accelerate the reaction by lowering the LUMO energy. substituted quinone. 2.

If the quinone has a good leaving group (like a halogen in p-chloranil ), a nucleophile can displace it directly. This is a common route for synthesizing complex dyes and bioactive molecules. 5. Photochemical Reactions

This is the most common reaction for substituted quinones. A nucleophile (like an amine, thiol, or alcohol) attacks the double bond.

The "ortho/para" rule applies here; substituents on the diene and the quinone will orient themselves to maximize electronic stabilization in the transition state. 3. Redox Chemistry (Reduction) Quinones are easily reduced to hydroquinones.