Classification, Nomenclature and isomerism of organic compounds.pdf

unit 1 is complete

1. Mr. Dushyant
Global Research Institute of Pharmacy

2. Organic compound as a chemical compound that contains a carbon–
hydrogen or carbon–carbon bond; others consider an organic compound to
be any chemical compound that contains carbon.

For example, carbon-containing compounds as alkanes
such (e.g. methane CH
4) and its derivatives are universally considered
organic, but many others are sometimes considered inorganic, such
as halides of carbon without carbon-hydrogen and carbon-carbon
bonds (e.g. carbon tetrachloride CCl
4), and certain compounds of carbon
with nitrogen and oxygen (e.g. cyanide ion CN
−
, hydrogen
cyanide HCN, chloroformic acid ClCO
2H and carbon dioxide CO
2)

4. The compounds in which the carbon atoms form a chain-linked in a linear
pattern or branched are called as acyclic or open-chain compounds.

5. Open-chain compounds are further classified as:

Saturated compounds: The compound is saturated if single bonds connect
all of the carbon atoms in the chain. In this, all the valence of carbon are
satisfied by single bonds.

Unsaturated compounds: If there are double or triple bonds between the
carbon atoms, the compound is unsaturated. In this, all the valence of carbon
are satisfied by multiple bonds.

6. Cyclic compounds are organic compounds in which the carbon atom chain is
closed or cyclic. - It is two types like

(i) Heterocyclic compounds: the chain contains carbon as well as other atoms
such as oxygen, nitrogen, sulphur, and so on.

7. (ii) Homocyclic compounds (Carbocyclic compounds): Those in which
the chain contains only carbon atoms.




Homocyclic compounds are further classified as:

(i) Alicyclic compounds: Which have one or more carbocyclic rings that can
be either saturated or unsaturated.

8. (ii) Aromatic compounds: Chemical compounds that consist of conjugated
planar ring systems accompanied by delocalized pi-electron clouds in place of
Individual alternating double and single bonds. It contains sp
2
hybridized
carbon atoms and must obey the Huckel rule.

9. a) Benzenoid aromatic compounds

Benzenoid compounds are molecules that have at least one benzene
ring in its chemical structure. A benzene ring is a cyclic structure
having six carbon atoms as the ring members. It has three pi bonds
(double bonds) and three sigma bonds arranged in an alternative
pattern. Therefore, we call this pattern a conjugated pi () system.

Since the molecule has double bonds due to benzene ring, the
molecule is an unsaturated compound with extra stability provided
by the conjugated pi () system.

10. b) Non-benzenoid aromatic compounds

Non benzenoid compounds are aromatic compounds that having
conjugated systems with planar cyclic structure do not have benzene
rings in their structure.

11. The word IUPAC stands for International Union of Pure and Applied
Chemistry.

The purpose of IUPAC system of nomenclature is to establish an
international standard of naming compounds to facilitate communication.


IUPAC
Suffix Word Root Perfix
Substituents 2°
Cyclo/Biocyclo 1°
No. of
carbon in
main chain
Type of bond 1°
Functional Group 2°

12. IUPAC :-

2° Prefix + 1° Prefix + Word Root + 1° Suffix + 2° Suffix


Word Root :-

13. Functional Group :-
Type of Bond :-
(-) Bond : ane
(=) Bond : ene
(≡) Bond : yne

14. Number of Identical Substituents :-

15. 1. Longest chain rule :-

Selection the most C-C chain (may or may not br straight).
Numbering from that side, So that branch (substituents) gets lowest locant.
Naming always done alphabetically (2-bromo 4-ethyl 6 methyl heptane)

16. 2. Naming of Complex Substituents:-

While naming of complex substituents, gives 1
st
no. directly attached carbon
from main chain then follow IUPAC for substituents.

17. 3. Naming of Cycloalkanes :-

While naming of carbocyclic compounds, we have to add the prefix
‘cyclo’ before the chain.
If ring and chain both have same numbers of Carbons then for main
chain. (Ring > chain)

18. 4. Naming of unsaturated hydrocarbons ( Alkene & Alkyne) :-

Select longest C-C chain with maximim no. =/≡ bonds.
Numbering in such a way that =/≡ bonds get lowest locant.
(=/≡) > substituents
Normally both = and ≡ bond have same priority, but in case of tie. (= > ≡)
While naming if a, e, i, o, u, y come after one another then previous one
deleted
If both ring and chain present sim., selected one with maximum =/≡ bonds.

19. 5. Naming of Functional Group :-

Functional group are the atoms or group of atoms which gives all
properties to a compounds
Numbering from that side so that functional group lowest locant.
 F.G > = > ≡ > substituents

20. Alcohols are named by replacing the suffix -ane with -anol. If there is more
than one hydroxyl group (-OH), the suffix is expanded to include a prefix
that indicates the number of hydroxyl groups present (-anediol, -anetriol,
etc.).
The position of the hydroxyl groups on the parent chain is indicated by
placing the numbers corresponding to the locations on the parent chain
directly in front of the base name (same as alkenes).

21. Aldehydes are named by replacing the suffix -ane with -anal.
If there is more than one -CHO group, the suffix is expanded to include a
prefix that indicates the number of -CHO groups present (-anedial - there
should not be more than 2 of these groups on the parent chain as they must
occur at the ends).
It is not necessary to indicate the position of the -CHO group because this
group will be at the end of the parent chain and its carbon is automatically
assigned as C-1

22. Carboxylic acids are named by counting the number of carbons in the
longest continuous chain including the carboxyl group and by replacing the
suffix -ane of the corresponding alkane with -anoic acid.
If there are two -COOH groups, the suffix is expanded to include a prefix
that indicates the number of -COOH groups present (-anedioic acid - there
should not be more than 2 of these groups on the parent chain as they must
occur at the ends).
It is not necessary to indicate the position of the -COOH group because this
group will be at the end of the parent chain and its carbon is automatically
assigned as C-1

23. Isomerism is the phenomenon in which more than one compounds have the
same chemical formula but different chemical structures.

Chemical compounds that have identical chemical formulae but differ in
properties and the arrangement of atoms in the molecule are called isomers.
Therefore, the compounds that exhibit isomerism are known as isomers.

There are two primary types of isomerism, which can be further categorized
into different subtypes. These primary types are Structural Isomerism and
Stereoisomerism. The classification of different types of isomers is
illustrated below.

25. Structural isomerism is commonly referred to as constitutional isomerism.
The functional groups and the atoms in the molecules of these isomers are
linked in different ways.

Different structural isomers are assigned different IUPAC names since they
may or may not contain the same functional group.

The different types of structural isomerism are discussed in this subsection.

26. 1. Chain Isomerism:-

Chain isomers have the same molecular formula, but the way their carbon
atoms are joined together differs from isomer to isomer.

27. 2. Position Isomerism :-

The positions of the functional groups or substituent atoms are different
in position isomers.
Typically, this isomerism involves the attachment of the functional
groups to different carbon atoms in the carbon chain.
An example of this type of isomerism can be observed in the
compounds having the formula C
3H
7Cl.

28. 3. Functional Isomerism:-

It is also known as functional group isomerism.
As the name suggests, it refers to the compounds that have the same
chemical formula but different functional groups attached to them.
An example of functional isomerism can be observed in the compound
C
3H
6O.

29. 4. Ring Chain Isomerism :-

In ring-chain isomerism, one of the isomers has an open-chain structure
whereas the other has a ring structure.
They generally contain a different number of pi bonds.
A great example of this type of isomerism can be observed in C
3H
6.
Propene and cyclopropane are the resulting isomers, as illustrated
below.

30. 5. Metamerism :-
This type of isomerism arises due to the presence of different alkyl
chains on each side of the functional group.
It is a rare type of isomerism and is generally limited to molecules that
contain a divalent atom (such as sulphur or oxygen), surrounded by
alkyl groups.
Example: C
4H
10O can be represented as ethoxyethane (C
2H
5OC
2H
5)
and methoxypropane (CH
3OC
3H
7).

6. Tautomerism :-
A tautomer of a compound refers to the isomer of the compound which
only differs in the position of protons and electrons.
Typically, the tautomers of a compound exist together in equilibrium
and easily interchange.
It occurs via an intramolecular proton transfer.
An important example of this phenomenon is Keto-enol tautomerism.

31. THANKS