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.

Classification on the basis of carbon chain

1. Common naming system.

a) On the basis of source.



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—

Functional Group               Suffix


-CHO                                                 aldehyde

-COOH                                                IC acid

-COOR                                               alkyl-ate

-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 hydrocarbon…

    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

Functional 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.

Priority order for selection of carbon chain

(Functional group > multiple bond>number of carbon atom>substituents)

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

-o-N=O                                    nitrite

-OCH2CH3                             ethoxy

-CH2-Cl                                  Chloro methyl

-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 group(cyclo).

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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