IUPAC Nomenclature of

Organic Compounds

 

The systematic name of an organic compound consists of the following parts:

 

  1. A ROOT which designates the basic carbon skeleton.
  2. A PRIMARY_SUFFIX used to designate unsaturation in the carbon chain.
  3. A SECONDARY_SUFFIX added to designate the major functional groups.
  4. A PREFIX added before the root to designate alkyl branches off the main chain. Certain functional groups can also be designated by a prefix (instead of a suffix).

 

IUPAC Nomenclature of

Organic Compounds – Procedure for Building Up the Systematic Name

 

  1. Choose the longest carbon chain containing an unsaturation (C=C,Cº C) and the major functional groups. This chain is designated by the ROOT.
    For cyclic compounds, the prefic "cyclo-" is added before the root.
  2. Number the chain from one end so that the unsaturation (if present) and the major functional groups have the lowest numbers. N.B: functional groups which must appear at the end of a carbon chain eg aldehyde (-CHO), carboxylic acid (-COOH) and its derivatives, always have number 1.
  3. Designate the unsaturation and major functional groups with the appropriate primary and secondary SUFFIXES. The location of functional groups is indicated by the number of the carbon atom to which they are attached. For a multiple bond (C=C, Cº C), the number of the first carbon involved in such a bond is used as its locating number.
  4. Designate other substituents on the carbon chain by the appropriate PREFIXES. If more than one identical substituent is present, this is indicated by the additional prefix di-, tri- etc. The substituents are listed in alphabetical order, preceded by their locating numbers. Cyclic compounds are indicated by the prefix "cyclo".

 

ROOT

The ROOT designates the basic carbon skeleton.

CARBON

CHAIN

ALKANE

ROOT

ALKYL

GROUP

FORMULA

 

 

 

 

 

C1

Methane

meth-

methyl

CH3

C2

Ethane

eth-

ethyl

CH3CH2

C3

Propane

prop-

propyl

CH3(CH2)2

C4

Butane

but-

butyl

CH3(CH2)3

C5

Pentane

pent-

pentyl

CH3(CH2)4

C6

Hexane

hex-

hexyl

CH3(CH2)6

C7

Heptane

hept-

heptyl

CH3(CH2)5

C8

Octane

oct-

ocyl

CH3(CH2)7

C9

Nonane

non-

nonyl

CH3(CH2)8

C10

Decane

dec-

decyl

CH3(CH2)9

 

PRIMARY SUFFIX

The primary SUFFIX designates unsaturation in the carbon chain.

SUFFIX

ALKANE saturated hydrocarbon -ane

ALKENE C=C double bond -ene

ALKYNE Cº C triple bond -yne

If followed by a second suffix, the final "e" is dropped.

 

SECONDARY SUFFIX

The secondary SUFFIX designates the major functional groups:

 

FUNCTIONAL GROUP

 

SUFFIX

 

 

 

alcohol

(-OH)

-ol

amine

(-NH2)

-amine

alkyl halide

(-X; X= F, Cl, Br, I)

-halide

aldehyde

(-CHO)

-al

ketone

(-CO-)

-one

carboxylic acid

(-COOH)

-olc acid

ester

(COOR)

-oate

amide

(-CONH2)

-amide

acid halide

(-COX)

-oyl halide

 

 

 

 

PREFIX

The PREFIX is added before the root to designate alkyl branches off the main chain. Certain functional groups can also be designated by a prefix (instead of by a suffix).

FUNCTIONAL GROUP

 

PREFIX

 

 

 

Amine

(-NH2)

-amino

Halide

(-X; X = F, Cl, Br, I)

halo- (eg fluoro-)

Nitrile

(-CN)

cyano-

Ether

(-OR)

alkoxy-


Hydrocarbon branches off the main chain are designated by the prefix alkyl- (eg butyl- etc).

The following trivial names are commonly used for the respective alkyl groups:

(CH3)2CH- isopropyl

(CH3)3C- tertiary butyl (or tert-butyl)

For multiple branches off a main chain the ordering of the prefixes is based on alphabetical arrangement (first letter of prefix) with the numbering arranged to give the lowest set of numbers in an overall sense.

For example, the molecule shown is named 5-chloro-2,2-dimethylhexane
(5+2+2 is lower than 2+5+5 if the numbering had started at the other end of the alkyl chain.)