The six π electrons are thus delocalised and can move freely about the six carbon nuclei . The delocalised π electron cloud is attracted more strongly by the nuclei of the carbon atoms than the electron cloud localized between two carbon atoms . Therefore , presence of delocalised π electrons in benzene makes it more stable .
Aromaticity : - The compounds that follow the following features are to be considered aromatic .
� Planarity � Complete delocalization of the π electrons in the ring
� Presence of ( 4n + 2 ) π electrons in the ring where n is an integer ( n = 0 , 1 , 2 , . . .). This is often referred to as Hückel Rule .
Preparation of Benzene : � Cyclic polymerization of ethyne � Decarboxylation of aromatic acids
( iii ) Reduction of phenol : Phenol is reduced to benzene by passing its vapours over heated zinc dust
Physical properties :
1 . Aromatic hydrocarbons are non- polar molecules and are usually colourless liquids or solids with a characteristic aroma .