Suffix - IUPAC System of Naming Organic Compounds
The word root is associated to the suffix that may be primary or secondary or both of them.
(a) Primary suffix: A primary suffix is added to the word root to point out whether the carbon chain is saturated or not saturated.
Table
Type of carbon chain
|
Primary suffix
|
General name
|
|
Saturated (C - C)
|
-ane
|
Alkane
|
|
Unsaturated (C = C)
|
-ene
|
Alkene
|
|
Unsaturated (C º C)
|
-yne
|
Alkyne
|
If the parent chain comprises two, three or more triple or double bonds, after that the numerical prefixes like di (for two), tri (for three), tetra (for four), etc. are added to the primary suffix.
(b) Secondary suffix: After that a secondary suffix is added to the word root after the primary suffix to point out the functional group present in the organic compound.
Table
Class of org. compound
|
Functional group
|
Secondary suffix
|
|
Alcohols
|
-OH
|
-ol
|
|
Aldehydes
|
- CHO
|
-al
|
|
Ketones
|
> C = O
|
-one
|
|
Carboxylic acids
|
- COOH
|
-oic acid
|
|
Esters
|
- COOR
|
alkyl.... oate
|
|
Acid chlorides
|
- COCl
|
-oyl chloride
|
|
Acid amides
|
- CONH2
|
-amide
|
|
Nitriles
|
- Cº N
|
-nitrile
|
|
Amines
|
- NH2
|
-amine
|
|
Thiol
|
- SH
|
thiol
|
It might be noted that while adding the secondary suffix to the primary suffix, the terminal 'e' of the primary suffix (that is ane, ene and yne) is droped if the secondary suffix starts with a vowel but is retained if the secondary suffix starts with a consonant. As specified in the table below:
Organic compound
|
CH3CH2OH
|
CH3CH2CN
|
|
Word root
|
Eth
|
Prop
|
|
Primary suffix
|
an (e)*
|
ane
|
|
Secondary suffix
|
ol
|
nitrile
|
|
IUPAC name
|
Ethanol
|
Propanenitrile
|
The terminal 'e' from the primary suffix has been dropped as the secondary suffix that is 'ol' starts with a vowel 'o'.