UNIT I Benzene amp its derivatives PART I Electrophilic Aromatic Substitution Reactions Aromatic compounds Benzene undergo electrophilic aromatic substitution EAS Arene Ar H is the generic term for an aromatic ID: 1007100
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1. Topic : Reactions of BenzeneUNIT I : Benzene & its derivativesPART -I
2. Electrophilic Aromatic Substitution ReactionsAromatic compounds (Benzene) undergo electrophilic aromatic substitution (EAS).Arene (Ar-H) is the generic term for an aromatic hydrocarbon.The aryl group (Ar) is derived by removal of a H atom from an arene.
3. Benzene shows following reactions →
4. General Mechanism for ESR :In step 1: the electrophile reacts with two p electrons from the aromatic ringThe arenium ion is stabilized by resonance which delocalizes the charge
5. In step 2, a proton is removed and the aromatic system is regenerated.
6. 1. Halogenation of Benzene:Benzene reacts with chlorine or bromine in an electrophilic substitution reaction, but only in the presence of a catalyst and gives halobenzene.
7. Mechanism :
8. We should know;Halogenation of benzene requires the presence of a Lewis acid.Fluorination occurs so rapidly it is hard to stop at mono- fluorination of the ring (A special apparatus is used to perform this reaction).Iodine is so unreactive that an alternative method must be used.
9. 2. Nitration of Benzene :Nitration of benzene occurs with a mixture of concentrated nitric and sulfuric acids.
10. Mechanism :
11. 3. Sulphonation of Benzene:Sulphonation occurs most rapidly using fuming sulfuric acid (concentrated sulfuric acid that contains SO3)
12. Mechanism :
13.