General Rules For Nomenclature

   Naming of Organic compounds is done by knowing General Rules For Nomenclature. According      to the conventional System of IUPAC nomenclature, the name of an organic compound consists of      three parts:

1. Word Root: It is the basic unit of the name. It tells us the number of carbon atoms in the            principal chain. For chains containing one to four carbon atoms, special word roots are used.              These special word roots are derived from the common names of the corresponding alkanes. 

      For  chains containing five or more carbon atoms Greek numerals are used.

Chain Length	Word Root	Chain Length	Word Root	Chain Length	Word Root
C1	Meth-	C5	Pent-	C9	Non-
C2	Eth-	C6	Hex-	C10	Dec-
C3	Prop-	C7	Hept-	C11	Undec-
C4	But-	C8	Oct-	C12	Dodec-

   2.   Suffix: It tells us the functional groups present in the molecule. The suffix may be of two types:

                                I.            Primary Suffix: It tells us the linkage between the carbon atoms.

Type of linkage	Suffix	Type of linkage	Suffix
	-ane	> C = C <	- ene
	-yne

                                II.      Secondary Suffix: It tells us the characteristic functional group present in the organic compound. It is added to the name, after the primary suffix. Some common secondary suffixes are given below.

Functional Group	Suffix	Functional Group	Suffix
Alcohol                (-OH)	-ol	Acid halide   (-COX)	-oyl halide
Thio alcohol        (-SH)	-thiol	Amide            (-CONH2)	-amide
Aldehyde             (-CHO)	-al	Acyl group     ( RCO-)	-oyl
Ketone                 (>C=o)	-one	Cyanide ( )	-nitrile
Carboxylic acid (-COOH)	-oic acid	Amine           (-NH2)	-amine
Ester                  (-COOR)	R… -oate	Sulphonic acid    (-SO3H)	-sulphonic acid

Important: When using these secondary suffixes, the carbon of the functional group (if any) is counted in the principal chain.

1.        3. Prefixes: These indicate the substitution of other atoms or groups (not considered as principal      functional groups) in place of hydrogen atoms in the main chain of carbon atoms. Most commonly      used prefixes are alkyl groups and groups or atoms which are not considered as principal                     functional groups. e.g.

Substituent	Prefix	Substituent	Prefix
CH3-	Methyl -	CH3CH2CH2-	Propyl-
C2H5-	Ethy l-	CH3CH2CH2CH2-	Butyl-
F -	Fluoro -	- NO2	Nitro-
Cl -	Choro -	- OR	Alkoxy -
Br -	Bromo -	-N = N -	Diazo -
I -	Iodo -	-N = O	Nitroso -

Important: In case of alicyclic compounds, a primary Cyclo is put before the word root. In such cases the above menthioned prefixes can be considered as secondary prefixes.  e.g.