nitrationdiscuss - The nitration of bromobenzene occurs by...

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The nitration of bromobenzene occurs by formation of the nitronium ion. Nitric acid is not convenient because a hot mixture of concentrated nitric acid with any oxidizable material may explode. One safer procedure involves sulfuric acid as a source of protons which is protonated by the hydroxyl group. Then the group leaves as water. Now the nitronium ion is formed as a better electrophile. Having a halogen on the aromatic ring means that it is a deactivating group since it withdraws electrons from the ring. The bromine on bromobenzene are electronegative and withdraws electron density from a carbon atom through the sigma induction effect. But the bromine also has lone pairs that participate by pi-donation. Therefore, the two effects oppose each other. When the electrophile nitronium ion reacts at the ortho or para positions relative to bromine, an additional resonance structure called the bromonium ion can be drawn which the lone pair from bromine stabilizes the carbocation. Therefore, the otho and para structures with
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This note was uploaded on 11/12/2010 for the course CH 0000 taught by Professor Na during the Fall '09 term at University of Texas at Austin.

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nitrationdiscuss - The nitration of bromobenzene occurs by...

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