2. • Organic chemistry is the study of compounds of carbon.
• The organic compound is any chemical substance that
contains carbon, hydrogen and oxygen.
• Other compounds may include:
– Florine
– Chlorine
– Bromine
– Nitrogen
– Sulphur
– Phosphorus etc.
3. Classification of Organic compounds
Organic compounds
Open chain or aliphatic
compounds
Cyclic compounds
Heterocyclic compounds
Homocyclic compounds
Alicyclic compounds Aromatic compounds Heteroalicyclic
compounds
4. • Open chain / Acyclic / Aliphatic compounds:
Carbon atoms are linked to each other either in linear or
branched manner.
Eg: Propane
Butane
• Closed Chain / cyclic compounds:
These compounds have closed chain of atoms. They are of two
types:
Homocyclic or Carbocyclic compounds
Heterocyclic compounds
H 3 C CH2 C H 3
H3C CH2 CH2 CH3
5. • Homocyclic compounds:
The ring structure is made up of only carbon atom. They are of
two types:
Aromatic compounds
Alicyclic compounds
1. Aromatic compounds / benzenoid comounds: Compounds contain
one or more benzene rings in their structure. They have pleasant
odour.
Monocyclic aromatic ring
Eg:
Polycyclic aromaticring
Benzene
Naphthalene
Anthracene
6. 2. Alicyclic compounds: Cyclic compounds with ring structure
containing only one carbon atoms. They behave more like aliphatic
compounds.
Eg:
Cyclopropane Cyclobutane Cyclopentane
7. Eg: N
• Heterocyclic compounds (Non-benzenoid compounds):
Cyclic compounds in which the ring atoms are made up of
heteroatoms like nitrogen, oxygen and sulphur in addition to carbon.
H
O S
N
Pyridine
Pyrrole Furan Thiophene
Heterocyclic compounds
Monocyclic Polycyclic
Three
membered
Bicyclic
Four
membered
Five
membered
Six
membered
8. • Monocyclic Heterocyclic compounds:
Three membered rings: These rings have two carbon atoms and one hetero atom.
Eg:
Four membered rings: These rings have three carbon atoms and one hetero atom. These
rings are less stable due to strain.
Eg:
Five membered rings: These rings have four carbon atoms and one hetero atom.
Eg:
O
H
N S
Oxirane Aziridine Thirane
O NH S
Oxitane Azitidine Thietane
O
H
N S O
H
N S
Tetrahydrofuran Pyrrolidine Tetrahydrothiophene Furan Pyrrole Thiphene
9. Six membered rings: These rings have five carbon atoms and one hetero atom.
Eg:
Bicyclic Heterocyclic compounds: These rings contain two ring system, in which atleast
one ring contain heteroatom.
Eg:
Polycyclic Heterocyclic compounds: These rings contain more than two ring system, in
which atleast one ring contain heteroatom.
Eg:
O
H
N S O N S
Tetrahydropyran Piperidine Tetrahydrothiopyran Pyridine Pyran Thiopyran
N
N
N
H
Quinoline Isoqinoline Indole
N
Acredine
10. IUPAC system of nomenclature of organic compounds:
Common name: The common Name of a compound is one which has a
history behind and, is accepted on account of its long usage.
Systemic name: The Systematic Name of a compound is based on its
structure.
IUPAC which is commonly referred to as the IUPAC (International
Union of Pure and Applied Chemistry) System of Nomenclature. It was
published in 1957 and released in 1967.
11. IUPAC rule for assigning names to complex molecules:
• Names for Branched-chain hydrocarbons; and
• Names for other classes of compounds.
Naming of Branched chain hydrocarbons:
Rule 1: Select the longest continuous carbon chain in the molecule which
need not necessarily have to be horizontal (straight). This is called the parent
chain or 'main chain', while other chains attached to it are referred to as
'side-chains'.
The number of carbon atoms constituting the main chain determines the
parent name of the hydrocarbon.
As in both the cases longest chain contain six carbon atoms, therefore the
parent name of hydrocarbon is Hexane.
12. In case a molecule contain two carbon chains of the same length, the one that
carries larger number of branches is designated as: the parent chain.
Both structures contain six carbon in long chain, but II shows three branches
attached to parent chain. Therefore, the chain shown in II is selected as the
parent chain.
Rule 2: Number the carbon atom of the parent chain as 1, 2, 3, 4 etc. starting
from the end that gives the smallest possible number to the carbons carrying
the 8ubstituents or branches.
13. In case there are two or more substituents present on the parent chain, two
sets of locants are obtained according as the numbering is done from the left
or right.
Rule 3: Prefix the name of the substituents to the name of the parent
hydrocarbon and indicate its position on the main chain by writing before it
the locant. A hyphen (-) is inserted between the locant and the substituent
name.
the exact name of the substituent methyl group (CH3 ) is written as 3-methyl.
14. Rule 4: The complete name of the hydrocarbon is written as one word. Hence
the hydrocarbon.
Name of compound: 3-Methylhexane.
In case a number of substituents are present on the main chain, there names
are prefixed to the name of the parent hydrocarbon in alphabetical order,
inserting hyphen (-) in between the names of substituents.
Name of compound: 3-Ethyl-2-methylhexane
15. Rule 5: If the same substituent is present two or more times, this is indicated
by prefix di, tri, tetra etc. to the substituent name. The locants of individual
substituents are set off from each other by commas and separated from the
written name by a hyphen.
the names of the substituents are written in alphabetical order regardless of
multiplying prefixes di-, trio, etc. Thus ethyl comes before methyl in the name
of the following compound the prefix di being neglected for the purpose.
16. Rule 6: In case the substituent on the parent chain is a complex one
(containing more than 4 carbon atoms) it is named as a substituted alkyl
group whose carbon chain is numbered from the carbon atom attached to the
main chain. The name of the complex substituent is given in brackets to avoid
confusion with the numbers of the parent chain.
Name of compound: 5(1,2-dimethylpropyl)nonane.
.
17. Rule 7: The position of a double (or triple) bond in alkenes (or alkynes) is
indicated by prefixing the number of the carbon preceding such a bond, the
carbon chain being numbered from the end which assigns lower positional
number to the double (or triple) bond.
In second structure the longest carbon-chain containing double bond has five
carbon atoms and, therefore, the name of the hydrocarbon is 2·ethyl-l-pentene.
.
18. Names of other classes of compounds:
Other classes of compounds - alcohols, aldehydes, ketones, carboxylic acids
etc. The compounds belonging to these classes are called functional
compounds.
Monofunctional compounds: The compounds containing one functional
group are referred to as monofunctional. These are named as derivatives of
the parent hydrooarbons by the following rules :
Rule 1: Select the longest carbon chain bearing the functional group. 'This is
the parent chain and is numbered from the end that gives lower positional
number to functional group.
Rule 2: Write the name of the parent hydrocarbon and prefix the substituent
names.
19. Rule 3: Drop the terminat '-e' of the hydrocarbon name and add the suffix
assigned to the functional group present.
Rule 4: Insert the positional number of the functional group (separated by
hyphens on either side) before the name of the parent hydrocarbon.
Rule 5: Halo and nitrocompounds are always named as substitutted
hydrocarbons.
3,4-Dimethyl-1-hexanol
3-Methyl-1-pentanal 3-Penten-2-one
20. 2-Methyl-3-nitropentane 2-Methyl-1-butanoic acid
2-Methyl-3-hexyn-1-oic acid
Polyfunctional compounds: The organic compounds which contain two or more
different functional groups in the same molecule, are called Poly functional
compounds.
Rule 1:When there are many functional groups present in a molecule, only one
suffix can be used to form a systematic name. The group named as suffix is termed
the Principal group.
3-Hydroxy-1-butanoic acid
23. STRUCTURAL ISOMERISM
Isomers are molecules that have the same molecular formula but
differ from each other in physical or chemical properties and the
phenomenon is called as Isomerism.
Broadly isomerism is of two types:
(i) Structural Isomerism; and
(ii) Stereoisomerism.
Structural Isomerism: When the isomerism is simply due to difference in
the arrangement of atoms within the molecule, without any reference to
space, the phenomenon is termed as Structural Isomerism.
Stereoisomerism: When isomerism is caused by the different arrangements
of atoms or groups in space, the phenomenon is called Stereoisomerism. The
Stereoisomers have the same structural formulas but differ in the spatial
arrangement of atoms or groups in the molecule.
25. Chain or Nuclear Isomerism: This type of isomerism arises from the
difference in the structure of carbon chain which forms the nucleus of the
molecule. It is, therefore, named as Chain or Nuclear Isomerism.
Molecular formula: C4H10
Positional Isomerism: When two or more compounds have structural
formulas which differ only in the position of the substituent atom or group on
the carbon chain, these are called Position Isomers and the phenomenon is
termed Positional Isomerism.
Molecular formula: C3H7OH
H3C CH2 CH2 CH3
n - Butane
CH3
H3C CH
CH3
Iso- Butane
H3C
OH
CH2 CH2
n - Propyl alcohol
OH
H3C CH CH3
Iso - Propyl alcoho
26. Molecular formula: C6H4 (CH3)2
FUNCTIONAL ISOMERISM: When any two compounds have the same molecular
formula. but possess different functional groups, they are called Functional Isomers
and the phenomenon is termed Functional Isomerism.
H2C CH CH2 CH3
1-Butene
H3C CH CH CH3
2-Butene
o - Xylene m - Xylene
p - Xylen
Molecular formula: C4H8
O
H
3
C
C
H
2 C
H
2
C
H
3 H
3
C O
H
C
H
2 C
H
2
C
H
2
B
utyl alcohol
D
iethyl ether
4 10
Molecular formula: C H O
O
H3C
C
CH3 H3C
CH2
CH
O
Acetone Acetaldehyde
Molecular formula: C6H6 O
27. METAMERISM: The isomerism caused due to the unequal distribution of carbon
atoms on either side of the functional group in the molecule of compounds
belonging to the same class is called as Metamerism.
Molecular formula: C4H10 O
O
H3C C3H7 H5C2 C2H5
O
Methyl propyl ether Diethyl ether
