Aromatic Compounds PDF

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Summary

Aromatic CompoundsCyclohexanes are not planarConformational isomers can exist due to restricted rotationCyclic hydrocarbonsBenzene Empirical formula of CH  Molecular formula of C 6 H 6  Kekule introduced the ring structure  Resonance structure  Sp 2 hybradised- π bonding as well as sigma bonds ...

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Aromatic Compounds Cyclohexanes are not planar Conformational isomers can exist due to restricted rotation Cyclic hydrocarbons Benzene        

Empirical formula of CH Molecular formula of C6H6 Kekule introduced the ring structure Resonance structure Sp2 hybradised- π bonding as well as sigma bonds Benzene is planar instead of tetrahedral 6 electrons in pure p orbitals overlap to form a delocalised ring Delocalisation around the ring means the benzene is very stable

CH3-methylebenzene OH-Phenol (benzenol) NH2-phenyleamine COOH-benzoic acid C6H6-CH2-Benzyle Electrophilic Attack    

Electrons are exposed above and below the plane Attractive for electrophiles Benzene is very unreactive Electrophiles must be very strong

Reactivity of Benzene     1. 2.

Can be attacked by electrophiles but results in substitution of hydrogen not addition First step is energetically unfavourable (required lots of energy) RDS Breaking the stable delocalisation takes energy Second step is easier and happens more readily Electrophilic attack Proton loss

Haogenation 1. Chlorination 2. Bromination 3. Iodination Catalyst= Lewis acid e.g. AlX3 or FeX3

Nitration of Benzene  

Sulphuric acid used as a catalyst Nitronium ion is created...