Introduction to Heterocyclic Compounds PDF

# Welcome to Organic 3 ## A Course Content - **W1** Heterocyclic rings; Classification and nomenclature - **W2** Five-membered heterocyclic compounds. - **W3** Benzo fused five-membered heterocyclic compounds. - **W4** Five-membered heterocyclic compounds with two hetero atoms. - **W5** Six-membere...

# Welcome to Organic 3 ## A Course Content - **W1** Heterocyclic rings; Classification and nomenclature - **W2** Five-membered heterocyclic compounds. - **W3** Benzo fused five-membered heterocyclic compounds. - **W4** Five-membered heterocyclic compounds with two hetero atoms. - **W5** Six-membered heterocyclic compounds. - **W6** Benzo-fused ring system of pyridine nucleus. - **W7** Mid-term exam - **W8** Mid-term exam - **W9** Introduction to stereochemistry - **W10** Stereochemistry of different organic compounds - **W11** Chemistry of carbohydrate - **W12** Chemical reaction of carbohydrate - **W13** Introduction to spectroscopy - **W14** Elucidation of chemical structure of organic molecules. - **W15** Revision - **W16** Final exam ## B Marks Distribution | Task | Marks | |--------------|-------| | Activity | 10 | | Midterm | 15 | | Practical exam | 15 | | Final exam | 50 | | Oral exam | 10 | ## Heterocyclic Compounds **By: Dr. Mohamed Gamal** Lecturer of Pharmaceutical organic chemistry & Medicinal chemistry ### Heterocyclic compounds - Heterocyclic compounds are cyclic compounds in which one or more of the ring atoms are other than carbon. - The ring atom that is not carbon is called a heteroatom. - The most common hetero- atoms are N, O & S. ### Classification of Heterocyclic Compounds - **A.** Isolated system - **B.** Condensed system with benzenoid compounds - **C.** Condensed system with heterocyclic rings ### Naming of heterocyclic compounds #### Trivial name **A.** Saturated heterocyclic compounds - Pyrrolidine - Tetrahydrofuran - Tetrahydrothiophene **B.** Unsaturated heterocyclic compounds - Pyrrole - Furan - Thiophene **C.** Fused - 1H-Indole - 2H-Isoindole - Benzofuran - Isobenzofuran ### IUPAC #### A. Isolated system (monocyclic) **In the presence of N** | Atoms | Unsaturated | Saturated | |-------|-------------|--------------| | 3 | -irine | -iridine | | 4 | -ete | -etidine | | 5 | -ole | -olidine | | 6 | -ine | -perhydroine | | 7 | -epine | -perhydroepine | | 8 | -ocine | -perhydroocine | | 9 | -onine | -perhydroonine | | 10 | -ecine | -perhydroecine | **In the absence of N** | Atoms | Unsaturated | Saturated | |-------|-------------|--------------| | 3 | -irene | -irane | | 4 | -ete | -etane | | 5 | -ole | -olane | | 6 | -ine | -ane | | 7 | -epine | -epane | | 8 | -ocine | -ocane | | 9 | -onine | -onane | | 10 | -ecine | -ecane | **In the presence of N** | Atoms | Unsaturated | Saturated | |-------|-----------------|------------------| | 3 | 1H-Azirine | Aziridine | | 4 | Azete | Azetidine | | 5 | 1H-Azole | Azolidine | **In the absence of N** | Atoms | Unsaturated | Saturated | |-------|-------------------|---------------| | 3 | Oxirene | Oxirane | | 4 | 2H-Oxete | Oxetane | | 5 | Oxole | Oxolane | #### Rules for Naming: 1. Name the heteroatom as aza, oxa & thia for N, O & S 2. If more than 1 similar atom write di, tri,… (diaza, triaza, dioxa,…) 3. If 2 or more different atom the parent (suffix) ring is for N then S then O, but prefix O, S, N as prefix. 4. Numbering of the rings starts with the heteroatom and proceeds around the ring so as to give substituents (or other heteroatoms) the lowest numbers possible. 5. When two or more different heteroatoms are present, the no. 1 O>S>N 6. The state of hydrogenation: - Saturated system (suffix according to the table –iridide, -irane,…) - Only 1 hydrogen in the unsaturated system: Number the position oh hydrogen then write H then name the ring system. - More than 1 hydrogen in the unsaturated system: Number the position oh hydrogens then di or trihydro, then name the ring system. 7. If one substituent, number the ring starting from heteroatom in such away to give the substituent lowest possible number. 8. If more than one substituent, number the ring starting from heteroatom in such away to give the substituent lowest possible number and then arrange substituents alphabetically #### B. Condensed system with benzenoid comp In this system, the heterocyclic ring is the parent (suffix), and the benzo is the prefix. e.g. Benz[b]furan #### C. Condensed system with heterocyclic - **A.** The ring size is similar and only one hetero atom, the parent ring (suffix) is N>O>S. - **B.** If the ring size is different and only one hetero atom, the parent ring (suffix) is the largest single ring. ### To detect the parent ring 1. Only one ring, which contains nitrogen? Choose it as the parent ring. 2. Two rings have the same heteroatoms, but their size is different? Choose the larger. 3. Two rings of the same size but have different heteroatoms? Choose N>O>S. 4. Similar ring size but different numbers of heteroatoms? Choose the higher number of heteroatoms. 5. Similar ring size and numbers of heteroatoms? Choose the one with a higher variety of heteroatoms.