Discussion 13-relative rates

Discussion 13-relative rates - Discussion 12: Relative...

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Discussion 12: Relative Rates 1. EAS or eletrophilic aromatic substitution is a reaction in which an electrophile replaces a hydrogen atom on an aromatic system. There are many important types of aromatic substitutions, like aromatic sulfonation, aromatic halogenations, acylation and aromatic nitration. What we are going to concentrate on is aromatic halogenations, specifically with the bromine halogen. The basic chemical reaction can be viewed as Ar-H + Br2 -- (HOA) Ar-Br + HBr. Ar stands for arene. The arene attacking the electrophile to form a cation that is positively charged is the first step of the mechanism. The face that the cation has lost its aromaticity and the other fact that it has a positive charge on the molecule makes it unstable. Although, some stability is provided by resonance because the positive charge can be equally distributed through out the molecule. The second step of the mechanism is the donation of electrons from a Lewis base and the restoration of the aromaticity of the arene. The mechanism gets a little complicated when
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This note was uploaded on 12/04/2009 for the course CHE 210 taught by Professor Swinnea during the Spring '08 term at University of Texas at Austin.

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Discussion 13-relative rates - Discussion 12: Relative...

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