Organic Chemistry | Heterocyclic Compounds PDF

Organic Chemistry III Heterocyclic Compounds Lec.1 Organic Chemistry | Heterocyclic Compounds Contents : Introduction 3 Importance of Heterocyclic Compounds 4 Most common Heterocyclic rings 9 Nomenclature of Heterocyclic Compounds 15 Pyrrole 25 Organic Chemistry | Heterocyclic Compounds Introduction...

Organic Chemistry III Heterocyclic Compounds Lec.1 Organic Chemistry | Heterocyclic Compounds Contents : Introduction 3 Importance of Heterocyclic Compounds 4 Most common Heterocyclic rings 9 Nomenclature of Heterocyclic Compounds 15 Pyrrole 25 Organic Chemistry | Heterocyclic Compounds Introduction: Organic Chemistry | Heterocyclic Compounds Importance of Heterocyclic Compounds: 1. Used as solvents Organic Chemistry | Heterocyclic Compounds 2. Found as natural product Organic Chemistry | Heterocyclic Compounds 3. Found as biomolecules Organic Chemistry | Heterocyclic Compounds 4. Used as drug A. Quinolone as antimalaria for 400 years Organic Chemistry | Heterocyclic Compounds B. Imidazole as Amebecide C. Lactam as antibiotics Organic Chemistry | Heterocyclic Compounds Most common Heterocyclic rings : N-Heterocyclic rings Five-membered rings Organic Chemistry | Heterocyclic Compounds N-Heterocyclic rings Six-membered rings Organic Chemistry | Heterocyclic Compounds N-Heterocyclic rings Fused rings Organic Chemistry | Heterocyclic Compounds O-Heterocyclic rings Organic Chemistry | Heterocyclic Compounds S-Heterocyclic rings Organic Chemistry | Heterocyclic Compounds Heterocyclic rings with two different heteroatoms Nomenclature of Heterocyclic Compounds Organic Chemistry | Heterocyclic Compounds Nomenclature of Heterocyclic Compounds: Naming monoheterocyclic compounds with more than one heteroatoms Organic Chemistry | Heterocyclic Compounds 2. Indication of the position of hetero atoms: The highest priority: atom is #1 and continues in the direction that gives the next priority atom the lowest number Organic Chemistry | Heterocyclic Compounds 3. Indication of the position of saturated atoms: When a ring is partially saturated, the location of saturated atoms, may be designated by a “#H” Organic Chemistry | Heterocyclic Compounds If substituents present, their position should be identified by the number of the atoms bearing them and then they should be listed in alphabetical order. Organic Chemistry | Heterocyclic Compounds The words dihydro or trihydro or tetrahydro are used if two or three or four atoms are saturated. These words are preceded by numbers indicate the position of saturated atoms as low as possible Note: and followed by the corresponding fully Trivial name is a nonsystematic name of an organic compound. unsaturated trivial name. H 1N 2 1,2-Dihydro-pyridine Organic Chemistry | Heterocyclic Compounds Nomenclature of Fused Systems : A. Nomenclature of benzofused compounds: A benzene ring fused to a heterocycle is named by: Prefix: the word benzo. Letter in square brackets: indicating the position of fusion. Name of heterocyclic ring: (common or IUPAC name). Name= Benzo [letter]name of heterocyclic ring Organic Chemistry | Heterocyclic Compounds For designating the position of fusion the following rule is followed: 1. Numbering the H.C.R: When numbering a ring with one heteroatom, the heteroatom is #1 and continues in the direction that is closer to the fused bond. When numbering a ring with more than one heteroatom, the highest priority atom is #1 and continues in the direction that gives the next priority atom the lowest number. Organic Chemistry | Heterocyclic Compounds 2. The bonds of the heterocyclic ring are assigned by alphabetical letters staring with the 1,2-bond. Note: H.C.R= heterocyclic ring Organic Chemistry | Heterocyclic Compounds EXAMPLES : Pyrrole Organic Chemistry | Heterocyclic Compounds Pyrrole : What Is Pyrrole ? Pyrrole is an unsaturated five membered heterocyclic compound consists of nitrogen as heteroatom at 1 position. One of the important heterocyclic compound because many naturally occurring substances contain pyrrole ring. Eg: Alkaloids, haemoglobin, chlorophyll Organic Chemistry | Heterocyclic Compounds Its name derived from the fact that its vapours produce a bright red colour when brought in contact with a pine splint moistened with con. HCl. Greek word- Pyrros which means fiery oil. Molecular formula: C4H5N Organic Chemistry | Heterocyclic Compounds Physical properties: Pyrrole has a relatively high boiling point as compared to furan and thiophene, this is due to the presence of intermolecular hydrogen bonding in pyrrole. H-bonding Organic Chemistry | Heterocyclic Compounds Source: Pyrrole occurs in coal- tar and in bone oil. Obtained from dry distillation or pyrolysis of animal by-products such as horns, hooves and bones. Ehrlich Test: Pyrrole + p-dimethylaminobenzaldehyde  Intense Red colour. Organic Chemistry | Heterocyclic Compounds Isolated Bone oil Washing with Sulphuric acid to remove basic substances Washing with dil.alkali to remove acidic substances Fractional distillation Pyrrole removed by boiling with KOH Potassium salt of pyrrole formed Steam distillation PYRROLE Organic Chemistry | Heterocyclic Compounds Synthesis of Pyrrole: 1) Paal-Knorr synthesis 1,4-dicarbonyl compounds reacts with ammonia or primary amines to give pyrrole derivatives. Organic Chemistry | Heterocyclic Compounds 2) Hantzsch pyrrole synthesis Reaction of a-haloketones with β-ketoester in presence of ammonia gives pyrrole derivatives. Organic Chemistry | Heterocyclic Compounds 3) Knorr synthesis Cyclic condensation of a-aminoketone with β-ketoester gives pyrrole derivatives.