An outline of stereochemistry in simple terms. I wish it will be understandable and useful. Just go through it and enjoy learning. Rejoice in learning friends.

1. a a
b c
11/6/2020 1SOWMIYA SAMBASIVAN

2. PROSTEREOISOMERISM / PROCHIRALITY
• Prochirilty molecules are those which are converted into chiral
molecule in a single step.
• Prochirality may be the result of substitution reaction of sp³ carbon
with nucleophile.
OR
• Prochirality may be the result of addition reaction of sp²carbon to a
sp³ carbon with nucleophile. a a
b c
11/6/2020 2SOWMIYA SAMBASIVAN

3. Prochirality may be the result of substitution reaction of sp³ hybridized carbon
substituent.
a ab c
11/6/2020 3SOWMIYA SAMBASIVAN

4. Prochirality may be the result of addition reaction of sp² hybridized carbon.
11/6/2020 4SOWMIYA SAMBASIVAN

5. Topicity can be defined as geometrical or stereochemical relationship between homorphic groups /
ligands/ atoms and structure of the molecule.
Difference types of relationships are possible for homomorphic ligands/groups/atoms.
1.Homo topic(homo-same; topo-place)
2.Hetero topic(hetero-different; topo-place)
Ligands can not by itself be called homotopic or heterotopic , in order to use this terminologies a
comparison with other homomorphic ligand or ligands present either in the same molecule or in a
different molecule is necessary.
Two criteria are used to decide whether the ligands/groups are equivalent or not.
a. Substitution-addition reaction
b. Symmetry criteria
Are employed to determine the topic relationship of homomorphic ligands.
11/6/2020 5SOWMIYA SAMBASIVAN

6. NOTE:
Homomorphic groups/ligands/atoms:
The groups/ ligands/atoms which are in isolation look the same or superimposable mirror images of each
other are called homomorphic groups/ligands/atoms.
Incase of atoms they must be of same element example two H’s or two Br atoms.
If we isolate the two H’s, then they are same and super imposable to each other
hence they are called homomorphic hydrogen’s.
11/6/2020 6SOWMIYA SAMBASIVAN

7. Incase of groups ,they must have same constitution and configuration. For example two methyl or
two Ph groups of same chirality R or S. They are called homomorphic groups / ligands / atoms.
a a
b c
A. Homotopic ligands :
Two or more ligands that are identical when viewed in isolation but
individual replacement of two identical ligand by another give rise
to identical molecule ,then they are called homotopic ligands.
11/6/2020 7SOWMIYA SAMBASIVAN

8. a
b c
a
1) Substitution-addition criteria
Two homomorphic ligands are homo tropic if substitution of first one and other by
different test ligand leads to homomers or identitical product.
11/6/2020 8SOWMIYA SAMBASIVAN

9. a a
b c
b.Homo topic faces
Two face of a pi system or a double bond are homotopic if addition to
either faces gives same or identical product.
11/6/2020 9SOWMIYA SAMBASIVAN

10. a a
b c
2)Symmetry criteria
a. Homo topic ligands
Two homomorphic ligands are homotopic if they can interchange position by rotation around Cn axis.
11/6/2020 10SOWMIYA SAMBASIVAN

11. a ab c
b.Homo topic faces
Two faces of pi system are homotopic if they can interchange face
result in structure by rotation around C2 axis.
11/6/2020 11SOWMIYA SAMBASIVAN

12. a a
b c
Heterotopic ligands
Two or more ligands that are identical when viewed in isolation but individual replacement of identical ligands by
another ligad give rise to two structurally different(isomeric) molecules, then they are called heterotopic ligands.
Constitutionally hetero topic ligands
Two or more ligands in a molecule that are identical on individual replacement
by another ligand give rise to two molecules that constitutional isomer of each
other, then the original two ligands are said to be constitutionally heterotopic
ligands.
11/6/2020 12SOWMIYA SAMBASIVAN

13. a ab c Stereo chemically hetero topic
Two or more ligands in a molecule that are identical on individual
replacement by another ligand give rise to two moecules that are
enantiomers/super imposable mirror images of each other,then the original
two ligands are said to be enantiotopic ligands.
11/6/2020 13SOWMIYA SAMBASIVAN

14. a a
b c
a)Enantiotopic ligands
1.Substitution-addition criteria
Two homomorphic ligands are enantiotopic if substitution of first one and other by different ligand leads to
enantiomers.
11/6/2020 14SOWMIYA SAMBASIVAN

15. a a
b c
b)Enantiotopic faces
Two faces of a pi system or a double bond are enantiotopic if addition to
either face gives enantiomeric product.
11/6/2020 15SOWMIYA SAMBASIVAN

16. a a
b c
Molecules having stereo heterotopic ligands exhibit prochirality.
2.Symmetry criteria
a)Enantiotopic ligand
Two homomorphic ligands are enantiotopic if they can interchangeable
through plane of symmetry or centre of inversion or Sn axis.
11/6/2020 16SOWMIYA SAMBASIVAN

17. a a
b c
Example-1: Molecule with plane of symmetry (ϭ) containing homomorphic ligand is
enantiotopic.
Example 2:Molecules with improper axis of symmetry (Sn)
containing homomorphic ligand is enantiomer.
11/6/2020 17SOWMIYA SAMBASIVAN

18. a a
b c
b)Enantiotopic faces
Two faces are enantiotopic if they can interchange through plane of symmetry or center of inversion of Sn
axis.
11/6/2020 18SOWMIYA SAMBASIVAN

19. a a
b c
a)Diastereotopic ligands
Two or more ligands in a molecule that are identical on individual replacement by another ligand give rise to
two molecule that are diastereomers/non superimposable not mirror images of each other, then the original
two ligands are said to be diastereotopic ligands.
Substitution–addition criteria
Two homomorphic ligands are diastereotopic if substitution of first one and the other by different test ligand
not already attached to the molecule leads to diastereomers /non superimposable not mirror images.
11/6/2020 19SOWMIYA SAMBASIVAN

20. a a
b c
11/6/2020 20SOWMIYA SAMBASIVAN

21. a a
b c
b)Diastereotopic faces
Two faces of a carbonyl group adjacent to stereo center upon
addition reaction leads to diastereomers and possess diastereotopic
faces.
11/6/2020 21SOWMIYA SAMBASIVAN

22. a a
b c
Wash your NON-SUPERIMPOSABLE(hands)
Stay as TRANS(social distancing)
Stay as CHAIR(Home)
11/6/2020 22SOWMIYA SAMBASIVAN