If the quinone is unsymmetrically substituted, the nucleophile typically attacks the less hindered carbon or the carbon with the lowest electron density.
This is the most common reaction for substituted quinones. A nucleophile (like an amine, thiol, or alcohol) attacks the double bond.
) on the quinone accelerate the reaction by lowering the LUMO energy. reactions of substituted quinones
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)
This reversible redox cycle is how Coenzyme Q (Ubiquinone) transports electrons in the mitochondrial respiratory chain. 4. Nucleophilic Substitution ( SNArcap S sub cap N cap A r ) on the quinone accelerate the reaction by
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.
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 quinone. 2.
Large groups can hinder the approach of the diene, often dictating which face of the quinone is attacked.