Iupac nomenclature

a presentation for scholars......................

1. IUPAC IUPAC
NOMENCLATURNOMENCLATUR
EE

2. IUPAC SYSTEM OF NOMENCLATURE
A system of naming compounds in chemistry, IUPAC
stands for:
---International
---Union of
---Pure and
---Applied
---Chemistry

3. IUPAC System of Naming IUPAC System of Naming
Organic CompoundsOrganic Compounds

4. MR. AJAY KUMAR Sharma
Similarly, the compound H
3
C CH=CH CH
2
OH is systematically
named as: CH
3
3-Methylbut-2-ene-1-ol
PREFIX WORD ROOT PRIMARY
SUFFIX
SECONDARY
SUFFIX
PREFIX
WORD
ROOT
PRIMARY
SUFFIX
SECONDARY SUFFIX

5. So, let us start with THE WORD ROOTTHE WORD ROOT
It is the name corresponding to no. of
carbon atoms in the longest chain of
CARBON atoms in the organic compound.
To determine the word root we need to
learn the table given alongside.

No. of ‘C’
atoms
Word
Root
1 Meth
2 Eth
3 Prop
4 But
5 Pent
6 Hex
7 Hept
8 Oct
9 Non
10 Dec
11 Undec
12 Dodec

6. Now, let us come to the PRIMARY SUFFIXPRIMARY SUFFIX
It indicates the nature of the carbon atom chain selected.
primary suffix
Only single bonds between C atoms -ane
(also called saturated)
Presence of double bond between C atoms -ene
Presence of triple bond between C atoms -yne

If the parent chain contains two, three or more double
or triple bonds, then the numerical prefixes such as di
(for two) , tri (for three), tetra (for four) , etc. are
added to the primary suffix.

7. But what if both – double and triple bonds
are present between the C atoms???
CH C CH
2
CH
2
CH CH
2

hex-1-en-5-yne

Both ‘ene’ & ‘yne’ are
written But –ene comes
Before -yne.

8. This is the word that defines the ‘family’ or functional group in
the organic compound.
 The various functional groups with their corresponding suffixes
are:

Let us now concentrate on the SECONDARY SUFFIX SUFFIX
Functional
Group
Class of
compound
Suffix
-COOH Carboxylic acids-oic acid
-COOR Ester -oate
-COX
(X=F, Cl, Br, I)
Acyl halides -oyl halide

9. Functional
Group
Class of
compound
Suffix
-CONH
2
Acid amide-amide
-CN Nitriles-nitrile
-CHO Aldehyde -al
>C=O Ketones -one
-OH Alcohol -ol
-NH
2
Amine -amine
-C=C Alkene -ene
-C≡C- Alkyne -yne
Thus the compound,
CH
3
CH
2
CH
2
OH is Propanol.
•Prop is the word root.
•-ane is the primary suffix.
•-ol is the secondary suffix
Prop+ane+ol = Propanol.
Since the secondary suffix Since the secondary suffix
begins with a vowel ‘o’, begins with a vowel ‘o’,
the ‘e’ of –ane is removed.the ‘e’ of –ane is removed.

10. As the word indicates, it means something which is fixed or
attached before or at the beginning. Hence a prefix is written
before the word root.
These are also of two types:
a)) Primary Prefix
b)) Secondary Prefix
Let us now come to what we call as PREFIXPREFIX

11. It is the word which helps us to distinguish between a cyclic and
an acyclic compound. The prefix CYCLO is used for cyclic
compounds only.
Therefore,

is cyclopentane while CH
3
CH
2
CH
2
CH
3
is pentane.

CH
2
CH
2
CH
2
CH
2
CH
2

12. Functional
Group
Prefix
-COOH Carboxy-
-SO
3
H Sulpho-
-COOR Alkoxycarbony-
-COCl Haloformyl-
-CONH
2
Carbamoyl-
-CN Cyano-
-CHO Formyl-
>C=O Keto-/oxo-
-OH Hydroxy-
-SH Mercapto-
-NH
2
Amino-
Thus the compound:

CH
3 –– CH –– CH
2 –– CH
2––

OH
Cl
Word root- But
Primary suffix- ‘-ane’
Secondary suffix- ‘-ol’
Prefix- Chloro
1 2 3
4
IUPAC name,
3-chloro butane-1-ol
Functional
group

13. Certain groups in organic chemistry are written as prefixes.
They are regarded as substituents. These groups along with
their prefixes are as follows:
Sl no. Substituent Secondary prefix
1 -F Fluoro-
2 -Cl Chloro-
3 -Br Bromo-
4 -I Iodo-

14. Note that the word
root will come after
the prefix. Thus, the
compound ,
is 2-chlorobutane.
CH
3
CH CH
2
CH
3
Cl
Sl no. SubstituentSecondary prefix
5 -NO
2
Nitro-
6 -NO Nitroso-
7 -N N- Diazo-
8 -OCH
3
methoxy
9 -OC
2
H
5
ethoxy
10 -OH Hydroxo
11 -NH
2
Amino

15. Different classes of
Organic Compound

16. HydrocarbonHydrocarbon
•saturated hydrocarBonssaturated hydrocarBons
(i) Alkanes
General formula:- C
n
H
2n+2
Suffix:- ane
1) These are the organic compounds which
contain only carbon-carbon single bonds.
2)According to IUPAC system, these are
named as alkanes.

17. Various memBers of the series are giVen
Below:
n-HexaneHexaneCH
3
(CH
2
)
4
CH
3
n-PentanePentaneCH
3
(CH
2
)
3
CH
3
n-ButaneButaneCH
3
CH
2
CH
2
CH
3
PropanePropaneCH
3
CH
2
CH
3
EthaneEthaneCH
3
CH
3
MethaneMethaneCH
4
common nameiuPac nameformula

18. (ii) Alkyl radical or Alkyl group(ii) Alkyl radical or Alkyl group
General formula:- C
n
H
2n+1
Suffix: -yl
3)Alkyl group contains only one H atom less than
the alkane.
4)The alkyl group is named by substituting the
suffix ‘ane’ of the name of the corresponding
alkane by ‘yl’. For e.g.:-
CH
4
, Methane becomes CH
3
- Methyl

19. imPortant alkyl grouP

20. (B) unsaturated hydrocarBons(B) unsaturated hydrocarBons
These are the hydrocarbons which contain
carbon to carbon double bonds or carbon to
carbon triple bonds in their molecules.
These are further classified into two types:
(iii)Alkenes
(iv)Alkynes

21. i) Alkenes
General formula: C
n
H
2n
Suffix: -ene
•The molecules containing one carbon-carbon
double bonds are called alkenes.
•In IUPAC system, the name of alkenes is
derived by replacing suffix ane of the
corresponding alkane by ene.
CH
3
-CH
3
CH
2
=CH
2
Ethane Ethene

22. Some Alkene groupSome Alkene group

23. ii) alkynes
General formula: C
n
H
2n-2
Suffix: -yne
•Alkynes are unsaturated hydrocarbons
with a triple bond between carbon-carbon
atom.
•Alkynes are named in the same way as
alkenes i.e., by replacing suffix ane of
alkane by yne.

24. Some Alkyne groupSome Alkyne group

25. Alkyl halidesAlkyl halides
General formula: C
n
H
2n+1
X or RX
Prefix: Halo
These are obtained from alkanes by the
replacement of one or more hydrogen atoms by
halogen atoms:
RH → RX
(X=F, Cl, Br, I)
-H,+X

26. In the IUPAC system, they are named as halogen
substituted alkanes i.e., haloalkanes. Thus the
name of halogen compound is given by prefixing
flouro, Chloro, bromo, iodo to the names of the
alkane. For e.g.
CH
3
Cl – chloromethane,
CH
3
CH
2
Cl – chloroethane etc.
Alkyl halidesAlkyl halides

27. alcoholsalcohols
General formula: C
n
H
2n+1
OH or ROH
Functional group : -OH
Suffix : -ol
1) These are derived by replacing one hydrogen
atom from an alkane by one hydroxyl group.
2) In IUPAC system, these are called alkanols and
their names have been derived by changing -e of
corresponding alkane by –ol

28. Some alkane and their alcohols

29. ethersethers
General formula: C
m
H
2m+1
OC
n
H
2n+1
Functional group: - O -
Suffix: -ol
These are derived from alkanes by replacing one
hydrogen atom by alkoxy group(-OR).
For e.g.
methoxy(OCH
2
)
ethoxy(OC
2
H
5
) etc.

30. aldehydesaldehydes
General formula:C
n
H
2n+1
CHO(where n can be 0 also e.g. HCHO)
Functional group: -CHO
Suffix: -al
These compounds are obtained by replacing a hydrogen atom
attached to the terminal carbon atom in alkane molecule by an
aldehydic (CHO) group. The first member is, however,
obtained by replacing a hydrogen atom in the hydrogen
molecule.

31. These are called alkanals in the IUPAC
system of nomenclature and the names of
individual members are derived by changing –e
of corresponding alkane by –al.
aldehydesaldehydes

32. Aldehydes and their formulasAldehydes and their formulas

33. KetonesKetones
General formula: C
n
H
2n+1
COC
m
H
2m+1
Functional group: >C=O
Suffix: -one
These are obtained by replacing two hydrogen atoms
attached to the non-terminal carbon atom in alkane
molecule by a divalent oxygen atom. Thus the functional
group called ketonic group contains a carbon atom joined
to the oxygen atom by double bond.
The names of individual members are derived by replacing
–e of the corresponding alkane by –one.

34. Carboxylic acidCarboxylic acid
General formula: CnH2n+1—COOH
Functional group: -COOH
Suffix: -oic acid
•In this compounds, one hydrogen atom in alkane
molecule is replaced by a carboxyl (COOH) group.
The first member is, however, obtained by replacing a
hydrogen atom in the hydrogen molecule.
•In the IUPAC system, they are named by replacing the
terminal –e of the corresponding alkane by –oic acid.

35. aminesamines
General formula: C
n
H
2n+1
-NH
2
Functional group: -NH
2
Suffix: -amine
These are the alkyl derivatives of ammonia. They
are formed by replacing one, two or all the three
hydrogen atoms in ammonia with alkyl radicals.
In IUPAC, the name is derived by replacing –e of
alkane by amine.

37. RULES FOR NAMING RULES FOR NAMING
AN ORGANIC AN ORGANIC
COMPOUNDCOMPOUND

38. 1. Longest chain rule
1)Determine the longest continuous (not
necessarily straight) chain of carbon atoms.
The base name corresponds to the number of carbon atoms in
the longest chain.
The full name for the alkane will include the names of any
branches.
CH
3CHCH
2CH
2CH
2CH
3
CH
3 Longest
chain
Alkyl group

39. 2. Position of the substituent2. Position of the substituent
Number of the carbon atoms in the parent chain
as 1,2,3…etc. starting from the end which gives
lower number to the carbon atoms carrying the
substituents i.e. Always number from the end of
the longest chain closest to the first branch.
X X
C-C-C-C-C C-C-C-C-C

1 2 3 4 5 5 4 3 2 1
SubstituentWRON
G
CORRECT

40. 3. Lowest set of locant rule3. Lowest set of locant rule
When two or more substituents are present, then end of
the parent chain which gives the lowest set of locants is
preferred for numbering.
Number the chain so as to give the lowest number
possible to the :
FUNCTIONAL group followed by
DOUBLE BOND,
TRIPLE BOND & finally the
SUBSTITUENT

We would call it
the
FDTS rule!

41. COOH CH CH CH
2
CH
2
Cl
So in the above compound numbering is possible as:
COOH CH CH CH
2
CH
2
Cl
1 2 3 4 5
12
34
5
COOH CH CH CH
2
CH
2
Cl

42. So which one is the correct numbering
according to the above rule??
3. If you notice in the above example, in SET 1 the functional
group is
_
COOH and it has a Carbon in it. In such cases, the
Carbon of the functional group always gets the position no. 1.

43. 4. What if the same functional group exists twice in the chain
HOH
2
C CH
2
CH
2
CH
2
OH
Here, irrespective of the end you start from, you get the same
position number both ways.
PLEASE be careful not to number the oxygen in the functional
group. You only have to number the C atoms in the chain.
Hence the compound is, Butane-1,4-diol .
WHERE… But + ane + 1,4 - diol
1234
Word rootPrimary
Suffix
Locant Secondary
Suffix

44. NOTE:-
–The position number of each of the functional
groups is expressed by the position number of C-
atom to which it is attached and it is known as
‘Locant’. The locants are separated from each other
by ‘commas’.
–The locant and the word are separated by a ‘hyphen’.
–The numerical prefixes –di, -tri, -tetra etc. are used
to indicate the presence of two, three or more like
groups.

45. Let us try naming the compound , which we had taken as an
example
HOOC CH CH H
2
C CH
2
Cl
The compound would thus be named as,
NOTE:- If the locant is not specified, it is taken as 1
1 2 3 4 5

46. For the same substituent at equivalent position, the ‘first point of
difference’ rule is applicable e.g.
CH
3
CH
3
H
3
C C H
2
C H
2
C CH CH
3
The locant positions are 2,2,5
CH
3
in Set 1 and 2,5,5 in Set 2.
CH
3
C

CH
2
CH
2
CH CH
3
1 2 3 4 5
6
1234
5
6
CH
3
CH
3
CH
3 Notice that 1
st
locant is same,
in both sets, but 2
nd
locant in
Set 1 is smaller & hence Set 1 is
correct.


For the same substituent at equivalent position, the ‘first point of
difference’ rule is applicable e.g.
CH
3
CH
3
H
3
C C H
2
C H
2
C CH CH
3
The locant positions are 2,2,5
CH
3
in Set 1 and 2,5,5 in Set 2.
CH
3
C

CH
2
CH
2
CH CH
3
CH
3
CH
3 Notice that 1
st
locant is same,
in both sets, but 2
nd
locant in
Set 1 is smaller & hence Set 1 is
correct.

CH
3 Notice that 1
st
locant is same,
in both sets, but 2
nd
locant in
Set 1 is smaller & hence Set 1 is
correct.

47. •What if different substituents are present in equivalent
position ?
CH
3
CH
2
CH CH CH
2
CH
3
C
2
H
5
CH
3
OPTION A 3-Ethyl-4-methylhexane
OPTION B 4-Ethyl-3-methylhexane
Hence option A is correct. But ignore multiplying prefixes
i.e. di, tri etc. while considering the alphabetical order!
Wha t do YO U
think w ould be
the c orre c t
a ns w e r? ?
When confused about substituents , always remember
that we consider the ALPHABETICAL order.
OR

48. RULES FOR NAMING COMPOUNDS HAVING MORE THAN ONE
FUNCTIONAL GROUP & /OR SUBSTITUENT &/OR MULTIPLE
BOND.
3.In a class of students one student is elected as leader, while the
others are to follow. Similarly, when more than one functional
groups are present, one functional group is chosen as the
PRINCIPAL FUNCTIONAL GROUP—written as a suffix,
while others are regarded as substituents—written as a
prefixes.

49. 1.Now how do we decide the principal
functional group??
To remove any confusion, the functional groups are arranged
in a preference series as follows:
Carboxylic acid>Sulphonic acid>Anhydride>Ester>Acid
chloride>Acid amide>Nitrile>Aldehyde>Ketone>Alcohol>
Amines>Alkene>Alkyne .
The group higher in the preference series is written as a Suffix
While the one lower to it would be written as a Prefix.

50. S.No. Functional group PREFIX SUFFIX
1. -COOH Carboxy- -oic acid
2. -SO
3
H Sulpho- Sulphonic acid
3. -COO
-COO
Anhydride
4. -COOR Alkoxycarbonyl Alkyl…oate
5. -COCl Haloformyl- -oyl chloride
6. -CONH
2
Carbamoyl- -amide
7. -CN Cyano- Nitrile
8. -CHO Formyl -al
9. >C=O Keto/oxo -one
10. -OH Hydroxy- -ol
11. -SH Mercapto- -thiol
12. -NH2 Amino- -amine
13. >C=O< - -ene
14. -C C- - -yne
O
The corresponding prefix and suffix as given earlier for each
functional group can be compiled as the follows:

51. thanks for your kind
consideration
BY:-
Ashwani Kumar