1. Aromatic Heterocyclic Compounds

2. Aromatic Five-Membered Heterocycles

3. Pyrrole is an extremely weak base

4. Pyrrole
Also aromatic, but lone pair of electrons is delocalized, so much weaker base.
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5. 5-membered ring system 29

6. Other Heterocyclics
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7. Other Heterocyclics
indole
benzofuran
benzothiophene

8. Aromatic Six-Membered-Ring Heterocycles

9. Heterocyclic aromatic compound.
Pyridine
Heterocyclic aromatic compound.
Nonbonding pair of electrons in sp2 orbital, so weak base, pKb = 8.8.
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10. The pyridinium ion is a stronger acid than a typical
ammonium ion

11. Quinoline and isoquinoline are known
as benzopyridines

12. Some Biologically Important Heterocycles
Imidazole

13. Some Biologically Important Heterocycles

14. Pyrimidine has two basic nitrogens.
Basic or Nonbasic?
Pyrimidine has two basic
nitrogens.
Imidazole has one basic
nitrogen and one nonbasic.
Purine?
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15. Chlorophyll a

16. Porphyrin

17. BILE PIGMENTS (bilirubin and biliverdin)H e m v d N C O 3 2 - D A x a t on R c F + ,

18. Gallstones (bilirubin)
Collection of Pathological Department