Isomerism
1.0 Isomerism
2.0 Structural Isomerism
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
3.0 Tautomerism
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
4.0 Geometrical isomerism in the compounds containing C=N
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
5.0 Optical Isomerism
5.1 Optical Activity
5.2 Asymmetric carbon (or) Chiral Carbon
5.3 Optical isomerism in bromo chloro iodo methane
6.0 Optical isomerism in compounds having more than one chiral carbons
6.1 Elements of symmetry
6.2 Centre of Symmetry
6.3 Stereoisomerism in Tartaric Acid
6.4 Calculation of number of optical isomers
7.0 Optically active compounds having no asymmetric carbon
5.1 Optical Activity
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
3.2 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
4.2 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
5.2 Asymmetric carbon (or) Chiral Carbon
5.3 Optical isomerism in bromo chloro iodo methane
6.2 Centre of Symmetry
6.3 Stereoisomerism in Tartaric Acid
6.4 Calculation of number of optical isomers
Light is propagated by a vibratory motion of the `ether’ particles present in the atmosphere. Thus in ordinary light vibrations occur in all planes at right angles to the line of propagation. In plane polarized light the vibrations take place only in one plane, vibrations in other planes being cut off. Plane polarized light can be obtained by passing ordinary light through a Nicol prism.
Certain organic compounds, when their solutions are placed in the path of a plane polarized light, have the remarkable property of rotating its plane through a certain angle which may be either to the left (or) to the right. this property of a substance of rotating the plane of polarized light is called optical activity and the substance possessing it is said to be optically active.
The observed rotation of the plane of polarized light [determined with the help of polarimeter] produced by a solution depends on: (a) the amount of the substance in tube; (b) on the length of the solution examined; (c) the temperature of the experiment; and (d) the wavelength of the light used.
The instrument used to measure angle of rotation is called polarimeter. The measurement of optical rotation is expressed in terms of specific rotation $[\alpha ]_D^t$; this is given by the following relation:
$$[\alpha ]_D^t = \frac{{{\alpha _{obs}}}}{{\ell \times c}}$$
where $\alpha = $ observed angle of rotation
$[\alpha ]_D^t = $ specific rotation determined at t°C, using D-line of sodium light.
$\ell = $ length of solution in decimeters
$C = $ concentration of the active compound in grams per milliliter.
For example, the specific rotation of amyl alcohol [2-methyl-1-butanol] at $25^\circ C$ for D-line of sodium light is given by.
The sign attached with the angle of rotation signifies the direction of rotation. Negative sign $(–)$ indicates that the rotation is towards the left, while positive $(+)$ sign means that the direction of rotation is toward right.
The rotation may be different in different solvents and this needs to be mentioned while reporting the specific rotation. Thus,
$[\alpha ]_D^{25^\circ } = + 24.7^\circ $ (in chloroform)
