CH 106 - Lesson 2
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Even though they have pi bonding, aromatic compounds do not react using addition reactions as do the alkenes and alkynes. This is because the pi bonding is delocalized and spread around the benzene ring.

Substitution Reactions

Instead, aromatic compounds undergo substitution reactions in which one of the hydrogen atoms on the benzene ring is replaced by some other substituant. Substitution reactions generally require a catalyst and a source of energy (heat or light).

An example would be the reaction of benzene with chlorine in the presence of ferric chloride (catalyst, written above the arrow) to form chlorobenzene and chlorobenzene and hydrogen chloride.

  C6H6 + Cl2  C6H5Cl + HCl

Lab Work

You should keep this kind of reaction in mind while you are doing the lab work. If you are in the lab, you should do Part III of the experiment now. If not, be sure to it when you do come into the lab.


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