When benzene is treated with D2 SO4, deuterium slowly replaces all six hydrogens in the aromatic

step 1 Okay, so when you react benzene with deuterated sulfuric acid, D2S -O -4, all of the hydrogens w

When benzene is treated with D2 SO4, deuterium slowly...

Key Concepts

Electrophilic Aromatic Substitution

This is a reaction mechanism in which an electrophile replaces a hydrogen atom on an aromatic ring. In the reaction with D2SO4, the deuteron (D+) acts as the electrophile, temporarily breaking the aromatic ? system to form a sigma complex, which then quickly re-aromatizes by losing a proton. This mechanism is key to understanding how hydrogen atoms on aromatic rings can be substituted by deuterium atoms.

Acid-Catalyzed Hydrogen/Deuterium Exchange

Under acidic conditions provided by D2SO4, the reaction involves exchange of hydrogen with deuterium via protonation and deprotonation steps. The strongly acidic environment facilitates the formation of reactive intermediates that allow repetitive deuterium incorporation, eventually replacing all the hydrogen atoms. This exchange process is driven by the reversible nature of proton (or deuteron) removal and the re-establishment of aromaticity.

Aromaticity and Resonance Stabilization

Benzene is an aromatic compound with a conjugated ?-electron system, which confers extra stability to its ring structure. The reaction pathway involves a temporary loss of aromaticity when an electrophile attacks, but the system quickly regains resonance stabilization after the substitution is complete. This inherent stability of the aromatic ring is vital for the controlled and reversible replacement of hydrogens with deuteriums.

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