Heterocyclic - Structures and Seq. Nos.
| Benzimidazole | Benzo[b]furan |
 |  |
| Benzothiazole | Benzo[b]thiophene |
 |  |
| Benzoxazole | |
 | |
| Carbazole | 2H-Chromene |
 |  |
| Cytosine |  |
| Furan | |
 | |
| Hydantoin | |
 | |
| Imidazole | Imidazolidine |
 |  |
| Imidazoline | Indane |
 |  |
| Indazole | Indene |
 |  |
| Indole | Indoline |
 |  |
| Isoindole | Isoquinoline |
 |  |
| Morpholine | |
 | |
| Oxirane | |
 | |
| Parathiazine | Phenothiazine |
 |  |
| Piperazine | Piperidine |
 |  |
| Purine | 2H-Pyran |
 |  |
| 4H-Pyran | Pyrazole |
 |  |
| Pyrazine | Pyrazolidine |
 |  |
| Pyridazine | Pyridine |
 |  |
| 2-Pyridone | Pyrimidine |
 |  |
| Pyrrole | Pyrrolidine |
 |  |
| Pyrroline | |
 | |
| Quinoline | 2-Quinolone |
 |  |
| Succinimide | |
 | |
| Tetrazole | 1,3,4-Thiadiazole |
 |  |
| 4-Thiazolidinone | |
 | |
| Thiophene | 1,3,5-Trioxane |
 |  |
| Uracil | |
 |