Pyridine and Pyrrole Two Aromatic Heterocycles

Problem 1S.7 Cyclooctatetraene readily reacts with potassium metal to form the cyclooctatetraene dianion, Why do you. suppose this reaction occurs so easily What geometry 

Pyridine, an aromatic heterocycle, has a it electron arrangement much like that of benzene. 

P5Trole (two r s, one Z), another example of an aromatic substance, is a five-membered heterocycle and has a tt electron system similar to that of the cyclopentadienyl anion. Each of the four sp -hybridized carbons has a 

Note that the nitrogen atoms have different roles in pyridine and pyrrole even though both compounds are aromatic. The nitrogen atom in pyridine is in a double bond and therefore contributes only tt electron to the aromatic sextet, just as a carbon atom in benzene does. The nitrogen atom in pyrrole, however, is not in a double bond. Like one of the carbons in the cydopentadienyl anion, the pyrrole nitrogen atom contributes two ir electrons (the lone pair) to the aromatic sextet. 

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