Isomerism
Isomerism
Definition
Isomers have same molecular
formula but different structures
or configurations of compounds.
Isomerism is resultant
Concept Ladder
factor of thermodynamic
system “entropy”.
y Isomers have same molecular formula but
different physical and chemical properties.
y Compounds having same molecular formula,
but different connectivity, different bonding
pattern (structural isomerism) or different 3-D
relative arrangement (stereoisomerism) is known
Previous Year’s Questions
as isomers and this phenomenon is known as
isomerism. Isomers of a substance must have
y Isomers are those which can be separated at the same
room temperature. [NEET-1991]
y Isomers always have same Degree of Unsaturation (1) structural formula
(DU) (2) physical properties
y Isomers are formed to satellite a system. (3) chemical properties
y Connectivity change (bonding pattern) structural (4) molecular formula
isomerism.
Isomerism
1.
, y C2H6O (DU = 0)
−δ +δ Rack your Brain
(1) Alcohol CH3 − CH2 − O− H
(2) Ether CH3 − O − CH3 How molecular structures
y Both compounds have different connectivity so affect the value of its entropy?
both are structural isomers.
y Que
Both are stereo isomers.
Isomerism
2.
, Definition
STRUCTURAL ISOMERISM
Ex. Same molecular fomula but
different connectivity of atoms
is known as structural isomers.
I. Chain Isomerism
(1) Degree of Unsaturation
Concept Ladder
(DU) also known as Double
Bond Equivalent (DBE).
(H+ X− N)
DU = (C+ 1) −
2
(2)
Definition
Compounds having same MF
(3) and same functional group but
different P.C.C. or side chain is
called chain isomers.
Rack your Brain
(4)
How many minimum C-atoms are
required to give chain isomers
for Alcohol?
(5)
Previous Year’s Questions
The isomer of ethyl alcohol is :
[AIPMT]
(1) diethyl ether
(2) dimethyl ether
Isomerism
(3) acetaldehyde
(4) acetone
3.
, NO. OF CARBON
S.NO. HYDROCARBON ISOMER 1 ISOMER 2
ATOMS
1. Alkane 4
2. Alkene 4
3. Alkyne 5
4. Alkediene 5
5. Alkenyne 5
6. Alcohol 4
II. Position Isomers
Compounds having same M.F., same figure same
P.C.C. or side chain but different position of Definition
functional group, multiple bonds & substituent.
Compounds have same M.F. but
difference in position of fucntion
group, multiple bond and
(1) substituent.
Both are Position Isomers
Isomerism
4.
Isomerism
Definition
Isomers have same molecular
formula but different structures
or configurations of compounds.
Isomerism is resultant
Concept Ladder
factor of thermodynamic
system “entropy”.
y Isomers have same molecular formula but
different physical and chemical properties.
y Compounds having same molecular formula,
but different connectivity, different bonding
pattern (structural isomerism) or different 3-D
relative arrangement (stereoisomerism) is known
Previous Year’s Questions
as isomers and this phenomenon is known as
isomerism. Isomers of a substance must have
y Isomers are those which can be separated at the same
room temperature. [NEET-1991]
y Isomers always have same Degree of Unsaturation (1) structural formula
(DU) (2) physical properties
y Isomers are formed to satellite a system. (3) chemical properties
y Connectivity change (bonding pattern) structural (4) molecular formula
isomerism.
Isomerism
1.
, y C2H6O (DU = 0)
−δ +δ Rack your Brain
(1) Alcohol CH3 − CH2 − O− H
(2) Ether CH3 − O − CH3 How molecular structures
y Both compounds have different connectivity so affect the value of its entropy?
both are structural isomers.
y Que
Both are stereo isomers.
Isomerism
2.
, Definition
STRUCTURAL ISOMERISM
Ex. Same molecular fomula but
different connectivity of atoms
is known as structural isomers.
I. Chain Isomerism
(1) Degree of Unsaturation
Concept Ladder
(DU) also known as Double
Bond Equivalent (DBE).
(H+ X− N)
DU = (C+ 1) −
2
(2)
Definition
Compounds having same MF
(3) and same functional group but
different P.C.C. or side chain is
called chain isomers.
Rack your Brain
(4)
How many minimum C-atoms are
required to give chain isomers
for Alcohol?
(5)
Previous Year’s Questions
The isomer of ethyl alcohol is :
[AIPMT]
(1) diethyl ether
(2) dimethyl ether
Isomerism
(3) acetaldehyde
(4) acetone
3.
, NO. OF CARBON
S.NO. HYDROCARBON ISOMER 1 ISOMER 2
ATOMS
1. Alkane 4
2. Alkene 4
3. Alkyne 5
4. Alkediene 5
5. Alkenyne 5
6. Alcohol 4
II. Position Isomers
Compounds having same M.F., same figure same
P.C.C. or side chain but different position of Definition
functional group, multiple bonds & substituent.
Compounds have same M.F. but
difference in position of fucntion
group, multiple bond and
(1) substituent.
Both are Position Isomers
Isomerism
4.
