(1) Optically active substance -> The substance which rotate the plane of polarised light are called optically active substance.
(2) Optically inactive substance -> The substance which do not rotate the plane of polarized light are called optically inactive substance.
(3) Polarimeter -> The angle by which the plane polarised light is rotated is measured by an instrument is called polarimeter.
(4) Dextrorotatory Substance -> The substance which rotate the plane of polarised light in clockwise direction is called dextrorotatory substance.
( 'd' or '+' sign) (d- form)
(5) Laevorotatory Substance -> The substance which rotate the plane of polarised light in anticlockwise direction is called laevorotatory substance.
( 'l' or '-' sign )
(6) Enantiomers -> The stereoisomers related to each other as non super imposable mirror image are called enantiomers.
* If one of the enantiomers is dextrorotatory then the other will be laevorotatory substance.
* Enantiomers possess identical physical properties like melting point, boiling point, solubility, refractive index, etc. They only the differ with respect to the rotation of plane polarised light.
(7) Racemic mixture or Racemic modification -> A mixture containing two enantiomers equal proportion will have zero optical rotation as the rotation due to one isomers will be cancelled by the rotation due to other isomers. Such a mixture is called racemic mixture or racemic modification.
Represented by 'dl' or '+- ' sign before the name.
Eg- +-butan-2-ol
(8) Asymmetric -> spatial arrangement of four groups around a central atom is tetrahedral and if all the substituent attached to that carbon atom are different such as carbon is called asymmetric carbon or stereocentre.
(9) chirality -> The objects which are non superimposable on their mirror image are said to be chiral image and this property is called chirality.
Eg- butan-2- ol
(10) Achiral -> The object which are superimposable on their mirror image are called achiral.
Eg- propan-2-ol
(11) Inversion -> The spatial arrangement of bonds to an asymmetric centre gets inverted during a chemical reaction or transformation is called inversion.
(12) Racemisation -> the process of conversion of enantiomers into a racemic mixture is called Racemisation.
(13) Retention -> It is the preservation of integrity of the spatial arrangement of bonds to an asymmetric centre during a chemical reaction or transformation.
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