What is the requirement for #"aromaticity"#? Why is cyclohexane non-aromatic?

1 Answer
anor277
Jul 7, 2016

A requirement for aromaticity is #4n+2# #pi# electrons

Explanation:

Benzene, #C_6H_6#, certainly meets this criterion; so does pyridine, #C_5H_5N#, and pyrrole, #C_4H_5N#, and furan, #C_4H_4O#, and thiophene, #C_4H_4S#. Cyclohexane has no #pi# electrons, and cyclohexene and cyclohexadiene have #2# and #4# #pi# electrons respectively.

The 5-membered ring aromatic heterocycles are so-called #pi-"excessive"# species, whose reactivity in electrophilic substitution is enhanced.

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