This document discusses different types of isomers, including constitutional isomers and stereoisomers. Stereoisomers differ in the spatial orientation of their atoms but have the same molecular formula and functional groups. There are several types of stereoisomers: enantiomers, which are non-superimposable mirror images; diastereomers, which are not mirror images; and meso compounds, which have an internal plane of symmetry and are optically inactive despite having multiple stereocenters. The document also discusses configuration, specific rotation, Fischer projections, and the distinguishing characteristics of enantiomers and diastereomers.

1. STEREOISOMERISM
Prepared by
Bhoopendra Patidar
GRY Institute of Pharmacy, Borawan
Khargone (MP)

2. Stereochemistry
• Isomers are different compound with same molecular formula.
• Two major classes of isomers are constitutional isomers and stereoisomers.
 Constitutional /Structural isomers have different IUPAC name, the same or
different functional groups, different physical properties and different chemical
properties.
 Stereoisomers differs only in way the atom are oriented in space. They have
identical IUPAC name (except for prefix like cis or trans). They always have the
same functional groups.
• A particular three-dimensional arrangement is called configuration.
• Stereoisomer differ in configuration.

3. A Comparison of constitutional isomers and streoisomers……

4. Classification of isomers
ISOMERS
Constitutional
isomers Stereoisomers
Enantiomers
(Mirror image)
Diastereomers
(Non mirror image)
Configurational
diastereomers
Cis-trans
diastereomers

5. Constitutional isomers
Constitutional isomers are isomers which have the same molecular formula
but differ in way their atoms are connected.

6. GEOMETRICAL ISOMERS

13. SPECIFIC ROTATION
• The angle of rotation of plan polarized light by a 1.00 gram per cm³
sample in a 1 dm tube.
 Specific rotation depends on the nature of substance, wavelength of light used,
concentration of the solution thickness of the layer, nature of the solvent and
temperature at which experiment is conduced.

17. CONFIGURATION
The arrangement of atom that characterize a particular stereoisomer is called
its configuration.
The following methods are used to assign the configuration:
A. Absolute configuration [ R and S system]
B. Relative configuration [ D and L system]

18. Fischer Projections and D/L Notation
 The first system for doing this was developed by Fischer Rosanoff around
1900.
 Fischer first developed a method for drawing carbohydrate in two
dimensions, and in convention with respect to the orientation, so as to
indicate their three dimensional structure, so called Fisher Projection.
 Fischer and Rosanoff then devised a notation for desinationg the
configurations of stereogenic centers, depicted Fischers Projections, as
either D and L.
The Symbol D and L DO NOT relate to sign of rotation of an optical active
molecule which is designated (+)- (or d )and (-)- (or l).

26. ENANTIOMERS
 Enantiomers are non super-imposable mirror image isomers.
 Enantiomers related to each other much like a right hand is related to left hand.
 Enantiomers are said to be chiral.
 Some times the term right-handed and left-handed are used to describe the
compound with an asymmetric carbon.

27. Characteristic Features of Enantiomers
 Enantiomers have identical physical properties (bp, mp, density, solubility and
refractive index) but there is deference in direction of rotation of plane polarized
light.
 They have identical chemical properties except in chemical reaction with other
optical active compound.
 They have different biological properties.
Eg. (+)-Dextrose play an important role in animal metabolism, where as (-)-Dextrose
is not metabolized.
 When equal quantity of enantiomers are mixed an optical active compound
racemic mixture is formed.

28. Stereomers of substance that are not mirror images of each other are termed
as Diastereomers.
 They have different physical properties like B.P, M.P, solubility, density
and refractive index etc.
 Diastereomers have different specific rotation but they may have same or
opposite sign of rotation.
DIASTEREOMERS

29. MESO COMPOUND
• A meso compound is a molecule with multiple stereocenters that is
superimposable on its mirror image.
• Meso compound are achiral compounds that has multiple chiral centers.
• Meso compounds are optically inactive.
• It has an internal symmetry plane that divides the compound in half.

30. A meso compound should contain two or more identical substituted
stereocenters. Also, it has an internal symmetry plane that divides the
compound in half. These two halves reflect each other by internal mirror. The
stereochemistry of stereocenters should “cancel out’’. What it means here is
that when we have an internal plane that splits the compound into two
symmetrical sides, the stereochemistry of both right and left side should be
opposite to each other and therefore, optical inactive.