Page 23 - Pharmaceutical Organic Chemmistry-3 (Theoritical book) 24-25

Clinical Pharmacy PharmD - 2024/2025 Level 2 Pharmaceutical Organic Chemistry-3 (PC 305)
b) When two or more different heteroatoms are present, oxygen takes precedence over

sulphur and sulphur over nitrogen for the number one position.

c) If different heteroatoms are present, numbering starts with the heteroatom which

gives the lowest set of numbers for all the heteroatoms.

d) The lowest set of locants is then arranged according to the priority rule which is

also considered by naming the heteroatoms.

The following are some examples of nomenclature of different heterocyclic

compounds

NH
N N
H H O O

1H-azirine azirdine oxirane oxaziridine

N
N H
N
H S H

azetidine thietane pyrrole pyrrolidine

(azole) (azolidine)