Priority order of Functional Groups for IUPAC nomenclature

Rule:

1) When an organic compound contains two or more different functional group, one functional group is selected as the principal functional group names given as suffixes, while the other groups are treated as substituent and given name as prefix.

2) When carbon containing functional group treated as substituent name gives as prefix then carbon of this functional group may or may not be included in parent chain.

3) When carbon containing functional group treated as principal functional group then name given as suffix & carbon of this functional group is includes in parent chain.

Priority Order

S.N.	Name	Functional Group	Prefix	Suffix

1.	Carboxylic acid	-COOH	Carboxy	Oic acid
2.	Sulphonic acid	-SO₃H	Sulpho	Sulphonic acid
3.	Anhydride	-CO-O-CO-	-	Oic anhydride
4.	Ester	-CO-O-R	Alkoxy Carbonyl	(Alkyl) oate
5.	Acyl halide	-CO-X (X = F, Cl, Br, I)	Halo carbonyl	Oyl halide
6.	Amide	CONH₂	Amido (Carbamoyl)	Amide
7.	Cyanide	-C ≡ N	Cyano	Nitrile
8.	Iso cyanid	-N ≡ C	Carbyl amino (isocyano)	Isonitrile
9.	Aldehyde	-CHO	Formyl	al
10.	Ketone	-CO-	Oxo	One
11.	Alcohol	-OH	Hydroxoy	ol
12.	Thio alcohol	-SH	Mercapto	Thiol
13.	Amine	-NH₂	Amino	Amine
14.	Double bond	-C = C-	-	Ene
15.	Triple	-C ≡ C-	-	Yne
16.	Halo	-X	Halo	-
17.	Ether	-O-	Alkoxy	-
18.	Nitro	-NO₂	Nitro	-
19	Nitroso	-NO	Nitroso	-

4) If an alicyclic ring is directly attached to carbon containing functional group, the carbon of functional group is not included in the parent name of alicyclic system. Name of highest priority group written as suffix name as in following table.

Functional group	Suffix	Prefix
-COOH	Carboxylic acid	Carboxy
-CHO	Carbaldehyde	Formyl
-COX (X = F, Cl, Br, I)	Carbonyl halide	Halo carbonyl
-COOR	Alkyl carboxylate	-
-CONH₂	Carboxamide	Carbomoyl
-CN	Carbonitrile	Carbonitrile