Introduction to the Nomenclature of Organic Chemicals

Introduction to the Nomenclature of Organic Chemicals

Mainly two nomenclature system are proposed for the naming
of organic compounds.

on the basis of carbon chain

1. Common
naming system.

a) On the basis of



Marsh gas (marshy place)


Acetic acid (vinegar)


Formic acid (Red ant)


Methyl alcohol ( wood spirit)

b) On the basis of
hydrocarbons (Radical independent).

No. of Carbon Atoms             Prefix

1C                                        form.

2C                                        acet

3C                                        propion

4C                                        butyr

5C                                        valer


    Three carbon with
one double bond—Acryl.

    Four carbon with
one double bond—

Group               Suffix


CHO                                                 aldehyde

COOH                                                IC acid

COOR                                               alkylate

COX                                          alkyl halide

CONH2                                               amide

CN                                             Onitrile

Radical dependent-  Number of Bond           Suffix


1)        Single
bond (-)               ane suffix

2)        Double
bond (=)             ene suffix

3)        Triple(≡) bond                yne suffix


For saturated hydrocarbon—CnH2n+2- Suffix used as -ane.

    If unbranched
hydrocarbon then use prefix (n)

     When one
methyl group is attached to the second C-atom of the continuous chain then iso
prefix is used.

    When Two
methyl group is attached to the second C-atom of the continuous chain then neo
prefix is used.

Note—when one
hydrogen group are removed from the alkane then radical is form and called
monovalent radical or alkyl. -CH3—methyl -C2H5—ethyl For unsaturated

    Double bond (CnH2n)—suffix
— ene

    Triple bond (CnH2n-2)—suffix
— yne

Note—unsaturated radical.

Ex -CH2=CH— vinyl. -CH2-CH=CH2 — Allyl.

If any functional group are attached to the radical then
direct functional suffix are used to radical. Name= prefix of R + Suffix of

Group             Suffix


-OH                                            alcohol

NH2                                          Amine

-O                                             ether

S                                              thio ether

X                                              halide

CN                                            Cyanide

CO                                           ketone.



A)  Selection of
longest continuous parent carbon chain. B) 
Numbering in selected parent carbon chain.

order for selection of carbon chain

(Functional group > multiple bond>number of carbon

Functional group-

Multiple bond—  Number of Bond        Suffix

1)        Single bond (-)              ane suffix

2)        Double
bond (=)           ene suffix

3)        Triple(≡) bond               yne suffix


No of carbon

Number of
Carbons               Root Word


1C                                           meth

2C                                           eth

3C                                           prop

4C                                           but

5C                                           pent

6C                                           hex

7C                                           hept

8C                                           oct

Substituents means

Substituents                        Prefix


R                                          alkyl

NH2                                       amino

oN=O                                    nitrite

-OCH2CH3                             ethoxy

-CH2-Cl                                  Chloro

-S-                                          thio

-X                                          Halo

Numbering of selected carbon chain— Priority order.

Functional group>multiple bond>substituents.

Procedure of naming.

(Secondary prefix—– primary prefix—– word)

(root—– primary suffix——- Secondary suffix. )

Secondary prefix means —
substituents with locants

Primary prefix means—cyclic

Word root means—number of
carbon chain.

Primary suffix means– – ane,
-ene, – yne.

Secondary suffix means—principle
fuctional groups.

Number and alphabets are
seperated by hyphen (-).Di,tri,iso,neo and cyclo are neither seperated by comma
nor by hyphen .

First latter of naming is
always capital letter and space required between naming.

If more than one substituents
then use alphabetical order of substituent names.


Heterocyclic rings which are used during the naming…

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