Page 20 - Pharmaceutical Organic Chemmistry-3 (Theoritical book) 24-25

Clinical Pharmacy PharmD - 2024/2025 Level 2 Pharmaceutical Organic Chemistry-3 (PC 305)

2. Systematic name (IUPAC/ Hantzsch-Widman)

IUPAC name = locants +Prefix + suffix

A- Monocyclic systems:

The systematic names for three to ten-membered monocyclic systems containing

one or more heteroatom are based on the Hantzsch-Widnman-system. The

following is a summary of the rules for systematic nomenclature:

Rule 1:

a) The kind of heteroatom present is indicated by the prefix oxa-, thia-, selena-,

aza-, phospha-, sila-, bora-, ... etc. for oxygen , sulphur, selenium, nitrogen,

phosphorus, silicon, and boron, respectively.

b) Multiplication of prefixes as dioxa-, dithia- and diaza- are used when the ring

contains two oxygen, two sulphur or two nitrogen atoms.

c) When two or more different heteroatoms are present, preference is given first

to the highest group in the periodic table and then to the lowest atomic weight as

follows: Priority: O > S > N.

➢ E.g. the prefix oxaza is used for one oxygen and one nitrogen and thiaza for

one sulphur and one nitrogen.