Arenes have considerable energetic stability because of the delocalised pi bonding electrons. Arenes require much more vigorous reaction conditions than alkenes to undergo addition reactions because of this extra stability.
Arene chemistry is dominated by electrpophilic substitution reactions that enable arenes to retain the delocalised pi electrons (ring). Hydrogen atoms on the benzene ring may be replaced by a variety of other atoms or groups including halogen atoms & nitro (-NO2) groups.
The variety of substituition reactions on benzene provides access to many useful compounds including medicines, dyes, explosives and polymers.
When the -OH group is joined directly to a benzene ring, the resulting alcohol is called a phenol.
Phenols are weakly acidic and form salts, called phenoxides, plus water on reaction with sodium hydroxide.
The reaction of sodium with phenol produces sodium phenoxide and hydrogen gas.
The -OH group enhances the reactivity of the benzene ring towards electrophiles. Bromine water is decolourised by phenol, producing a white precipitate of 2,4,6-tribromophenol.
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