IUPAC system and IUPAC rules of naming hydrocarbon

Nomenclature is the system of naming. With the existence of innumerable compounds of carbon, it has become necessary to follow a universal, rational system of naming. Such a system has been evolved by International union of pure and applied chemistry (IUPAC). By following this system, we can eliminate the confusion that arises due to usage of common names or trivial names.

Nomenclature of straight chain hydrocarbons

The IUPAC name of a straight chain hydrocarbon is divided into two parts:

i. Word root

ii. Suffix

Word root

Word root determines the number of carbon atoms in the compound. The word roots for compounds having five or more carbon atoms are derived from Greek numbers.

Chain lengthC1 C2 C3 C4 C5 C6 C7 C8 C9 C10
Word root Meth - Eth - Prop - But - Pent - Hex - Hept - Oct - Non - Dec -

Suffix

To determine the nature of the bond (single, double or triple) between the carbon atoms, primary suffixes are used.

HydrocarbonPrimary suffixGeneral name
Saturated C – C - aneAlkane
Unsaturated C = C - eneAlkene
Unsaturated C ≡ C - yneAlkyne

Nomenclature of saturated hydrocarbons (alkanes)

In the IUPAC nomenculature, alkanes end with '-ane'

Condensed FormulaWord rootPrimary suffixIUPAC name and Formula
1. CH4
2. CH
3CH3
3. CH
3CH2CH3
4. CH
3CH2CH2CH3
5. CH
3CH2CH2CH2CH3
Meth -
Eth -
Prop -
But -
Pent
- ane
- ane
- ane
-ane
- ane
Methane CH4
Ethane C
2H6
Propane C
3H8
Butane C
4H10
Pentane C
5H12

Nomenclature of unsaturated hydrocarbons

Alkenes

In the IUPAC nomenclature, alkenes end with '-ene'

Condensed FormulaEord rootprimary suffixIUPAC name and Formula
1. CH2 = CH2Eth -- eneEthene C2H2
2.CH3 - CH = CH2Prop -- enePropene C3H6
3.CH3 - CH2 - CH = CH2But -- eneButene C4H8
4.CH3 - CH2 - CH - = CH2pent -- enePentene C5H10

Alkynes

In the IUPAC nomenculature, alkenes end with '-yne'.

Condensed FormulaWord rootPrimary SuffixIUPAC name and formula
CH ≡ CHEth -- yneEthyne C2H2
CH3 - C ≡ CHProp -- ynePropyne C3H4
CH3 - CH2 - C ≡ CHBut -- yneButyne C4H6
CH3 - CH2 - CH2 - C ≡ CHPent -- ynePentyne C5H8

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