4.4 Number of Geometrical isomers

2.1 Chain or Nuclear Isomerism
2.2 ${C_5}{H_{12}}$ stands for three chain isomers
2.3 Cyclohexane and methyl cyclopentane are nuclear isomerism
2.4 Position Isomerism
2.5 Functional Isomerism
2.6 Metamerism
2.7 Ring Chain Isomerism

3.1 Structural requirement for tautomrism
3.2 Cause of tautomerism
3.3 Keto-enol tautomerim
3.4 Percentage Composition of Tautomeric Mixture
3.5 Triad System containing Nitrogen
3.6 Mechanism of tautomerism
3.7 Stereoisomerism
3.8 Geometrical Isomerism
3.9 Reason of Occurrence of geometrical Isomerism

4.1 Geometrical isomerism in the compounds containing N=N
4.2 Geometrical Isomerism in Cyclic Compounds
4.3 Stability of cis, Trans (or) Geometrical isomers
4.4 Number of Geometrical isomers
4.5 E and Z nomenclature of geometrical isomers

5.1 Optical Activity
5.2 Asymmetric carbon (or) Chiral Carbon
5.3 Optical isomerism in bromo chloro iodo methane

6.1 Elements of symmetry
6.2 Centre of Symmetry
6.3 Stereoisomerism in Tartaric Acid
6.4 Calculation of number of optical isomers

7.1 Alkylidene cyclo alkanes
7.2 Difference between Racemic mixture and Meso compound

(a) In compounds containing more than one double bond, the number of geometrical isomers (N) is given by the formula

$N = {2^n}$

where n = no. of double bonds with different substituents at each end.

For example, $R - CH = CH - CH = CHR$ has 4 isomers.

(b) When the ends of an alkene are the same and n is the no. of double bonds, then the no. of geometrical isomers is given as :

$N = {2^{n-1}} + \;{2^{p-1}}$

where $p = \frac{n}{2}$ when n is even

and $p = \frac{{n + 1}}{2}$ when n is odd.

For example: $C{H_3} - CH = CH - CH = CH - CH = CH - C{H_3}$ , has the no. of geometrical isomers.

$N = {2^{3-1}} + {2^{2-1}} = {2^2} + 2 = 4 + 2 = 6$