1.
NOMENCLATURE AND
ISOMERISM IN ORGANIC
COMPOUNDS

2.
Basics of Organic Compounds
 An organic compound should contain a carbon
– carbon link.
 An organic compound will have carbon and
hydrogen in large quantity; and it might also
have other atoms such as oxygen, nitrogen,
halogens etc
 Organic compounds are classified as
1. Open chain compounds : C-C has two or
more open ends
2. Closed chain compounds : C-C has no end; it
is always closed.

3.
Points to remember
 Carbon is tetra valent; i,e it will always form 4
bonds.
 If a carbon is sp3 hybridised then it will have
tetrahedral geometry and will consists of single
bonds with other carbon
 If a carbon is sp2 hydridised; then it will have a
trigonal planar geometry and will consist of double
bonds between carbon and carbon
 If a carbon is sp hydridised; then it will have a
linear geometry and will consist of triple bonds
between carbon and carbon.
 A double bond consists of one sigma and one pie
bond; while a triple bond consists of two pie bonds
and one sigma bond.

4.
Classification of organic
compounds
 Alkanes : CnH2n+2
 Alkenes : CnH2n
 Alkynes : CnH2n-2
 Arenes : CnHn
 These are hydrocarbons, i.e. compounds
containing only carbon and hydrogen.
 Arenes are always cyclic compounds (closed
chain)
 While alkanes, alkenes might be open chain, the
closed chain corresponding compounds are
known as cycloalkanes, cycloalkens.

5.
Functional groups strucutres

6.
Functional group prefix and
suffix
 It is an atom or group of atoms attached to the
carbon chain.
 FG priorities : -COOH > -CHO > >C=O > -OH
> >C=C< > alkynes

7.
Alkanes and cycloalkanes

8.
Alkenes and Alkynes

9.
Benzene and its derivates

10.
NOMENCLATURE
 IUPAC(International union of pure and applied
chemistry) nomenclature
 Common / Trivial
 IUPAC : contains certain rules for naming
organic compounds
 Common name : derived from origin of the
organic compounds

11.
Common names

12.
IUPAC system - Rules
 Identify the longest chain containing carbon
carbon linkage.
 Numbering :
 Identify the substituent in the chain, i.e.
functional groups, alkyl group or any other
atom that are not considered in the longest
carbon chain.
 Numbering is done from that end which is

13.
 Naming : Prefix is given to substituent group with
the position indicating the branching while the
longest carbon chain which is alkane, alkene etc
is suffixed.
 If there are same substituent repeated then
prefixed such as di, tri, tetra is added
 Thus the name of the compound is : 2,6-
dimethyloctane and not 3,7-dimethyloctane.
 Lowest locant rule : 2+6 =8 ; 3+7 =10 8<10, thus

14.
 If two different substituent are present, then
numbering is still done from the carbon end
closest to the substituent but the naming is
done alphabetically.
 The name of the compound is 3-ethyl-2-
methyloctane

15.
 If two substituent are attached at the same
position from both the end, then numbering is
done from the end which has less alphabetical
order
 3-ethyl-6-methyloctane

16.
More examples

17.
IUPAC with functional groups -
Haloalkanes
 Chloromethane 2-bromopropane Trichloromethane 1,1,1-
trichlroethane
 1,1-dibromo-2-chloroethane 1-chloro-3-flouropropane
1,1,3-trichloro-1,3,3-
triflouropropane

18.
 Answer
1. 2-chloro-2-methylpropane
2. 2-chloro-2,3-dimethylpentane
3. 1-chloro-2,2-dimethylpropane

19.
IUPAC - Alcohols
 2-methylbutan-2-ol 3,5-dimethylhexan-1-ol 6-methylheptan-3-ol

20.
 2-bromo-5-chloro-cyclopentanol
Prop-1,2,3-tri-ol
Prop-2-en-1-ol