Pyridine is a basic heterocyclic organic compound with the chemical formula C₅H₅N. It is structurally related to benzene, with one methine group replaced by a nitrogen atom. The pyridine ring occurs in many important compounds, including azines and the vitamins niacin and pyridoxine.
Pyridine is classified as aromatic on the basis of its properties.It is flat with bond angle of 120 degree ,the four carbon-carbon bonds are of the same length and so are the two carbon nitrogen bond. It resists addition and undergo electrophilic substitution. Its heat of combustion indicates a resonance energy of 23 calorie per mole.
Pyridine can be considered a hybrid of the kekule structures 1 and 2.We shall represent it as structure 3 in which the circle represent the aromatic
In electronic configuration,the nitrogen of pyridine is considerable a different from the nitrogen of pyrrole. In pyridine the nitrogen atom like each of the carbon atom is bounded by the other member by the SP2 orbitals.The third SP2 orbital of each carbon atom is used to for orbital of each carbon atom is used to for a bond to hydrogen.The third SP2 orbital of Nitrogen simply contain a pair of electron.
Five Membered Hetrocyclic Compounds:-
