The document summarizes the Cahn-Ingold-Prelog (CIP) system of stereochemistry nomenclature. It outlines the main rules for assigning priority to groups around a stereocenter and determining whether a molecule is R or S. Examples are provided to illustrate the rules, such as assigning priorities based on atomic number and distinguishing between cis and trans isomers. The importance of distinguishing between enantiomers is also briefly discussed.

1. CAHN-INGOLD-PRELOG
NOMENCLATURE
GUIDED BY: Prof. Mrs. J.S. MESHRAM
PRESENTED BY: BIJI SARO VARGHESE
DATE: 4 OCT 2017
RASHTRSANT TUKDOJI MAHARAJ NAGPUR UNIVERSITY
DEPARTMENT OF CHEMISTRY

2. I would like to thank Dr. Mrs. J.S. Meshram mam for
her constant guidance and support throughout the
completion of my presentation. I would like to thank
my seniors of their support. I would also like to thank
my friends and colleague who helped me directly and
indirectly. I would also like to thank my parents who
provided me all the facilities for completion of my
presentation.
ACKNOWLEDGEMENT
2

3. The Cahn-Ingold-Prelog (CIP)
Nomenclature
The system that we use
was devised by
R. S. Cahn
Sir Christopher Ingold
Vladimir Prelog
3

4. RULE 1:If four atoms attached to the
stereocenter are different ,priorities depend on
atomic numbers.
(S)-2-BROMOBUTANE
4

5. Higher atomic number outranks lower
atomic number
Br > F Cl > H
(Z )-1-Bromo-2-chloro-1-fluoroethene
higher
lower
Br
F
Cl
H
higher
lower
C C
5

6. RULE 2:If two atoms are isotopes of the same
element, the atom of higher mass number has
the higher priority
F H
C
D CH3
1 4
3
2
6

7. C bonded to 3 H’s
C bonded to C and 2 H’s
C bonded to O and 2 H’s
C bonded to 2 C’s
and one H
7

8. Evaluate substituents one by one.
Don't add atomic numbers within groups.
—CH2OH outranks —C(CH3)3
—C(O,H,H) —C(C,C,C)
8

9. RULE 4:If two carbon chains are attached to the
stereogenic carbon the chain with a secondary
carbon is of higher priority than the one with
primary carbon.
23
4
1
9

10. C O
H
C
O
O
C
H
C C H C
C
C
C
C
C
H
10

11. C OH
H3C
H
CH3CH2
CHO
CH3
H
CH2CH3
(S)-2-Butanol (R)-2-Butanol
RULE 6:To assign R and S configuration the
molecule has to be viewed with the lowest
priority group at the back.
11

12. Absolute Configuration
Rank the 4 groups (atoms) bonded to the chirality center
The R,S system of nomenclature
12

13. Naming Enantiomers -R,S System
Assigning Priorities to Groups
1. Oxygen (from CH2OH) = 16
2. Carbon (from CH2CH3) = attached to carbon
3. Carbon (from CH3) = attached to hydrogen
4. Hydrogen = 1
13

14. RULE 7:When the lowest priority group is
towards eyes interchanging of the position of
any two groups twice at stereocenter retains its
configuration and also puts group of lowest
priority away from the viewer.
First interchange Second interchange
H and CH3 CH3 and NH2
2
3
4
1 4
3
1
2
4
13
14

15. OH
H
CH3
CO2H
orient lowest priority
group away
OH
H3C CO2H
H
1
2
3
4
1
2
3
clockwise = R
OH
H
CO2H
CH3
orient lowest priority
group away
OH
HO2C CH3
H
1
3
2
4
1
3
2
counterclockwise = S
15

16. Br
F
Cl H
1
2
3
4
OH
CH2Br
CH3H
1
2
34
CH2CH3
H
CH=CH2Br1 2
3
4
21
3
12
3
R S
R-RECTUS S-SINISTER 16

17. 17

18. 18

19. CIS-TRANS NOMENCLATURE
RULE 8:In case of compounds of the type abC=Cab,
the isomer in which the identical groups are on the
same side of the double bond is called cis and if they
are on the opposite sides then they are called trans .
Cis-2-bromobut-2-ene Trans-2-bromobut-2-ene
19

20. C CC C
The E-Z Notational System
• E :higher ranked substituents on opposite sides
• Z :higher ranked substituents on same side
Entgegen Zusammen
higher
higherlower
lower
lower
higher
lower
higher
20

21. C has higher
priority than H
Cl has higher
priority than F
(Z)-1-chloro-1-fluoro-1-propene
21

22. This is the Z-stereoisomer.
22

23. S-enantiomer is teratogenic and R-enantiomer is sedative
IMPORTANCE OF
ENANTIOMER
23

24. 24

25. 25

26. IBUPROFEN
ONLY S-ENANTIOMER IS ANTI INFLAMATORY BUT R-
ENANTIOMER IS NON TOXIC AND INACTIVE
ONLY S-ENANTIOMER IS ANTI INFLAMATORY BUT R- ENANTIOMER IS NON TO
AND INACTIVE
26

27. 27

28. TARTARIC ACID
28

29. eferences
Stereochemistry by P.S. KALSI, seventh
edition,2008
Organic chemistry by Morrison and Boyd, sixth
edition,2007
Structures drawn by CHEM4WORD software
Web sources-
 https://pubchem.ncbi.nlm.nih.gov/compound/ibuprofen ,
 https://pubchem.ncbi.nlm.nih.gov/compound/thalidomide ,
 www.chemspider.com/Chemical-Structure.852.html ,
 https://chem4word.codeplex.com ,
29

30. 30