The document discusses the Woodward-Fieser rules, which can be used to theoretically calculate the lambda max (wavelength of maximum absorption) of conjugated systems and chromophores based on their structure. It provides examples of applying the rules to calculate lambda max for various compounds including conjugated dienes, alpha,beta-unsaturated carbonyls, and aromatic compounds. The rules take into account substituent effects and conjugation. The document notes that the theoretically calculated lambda max values usually match well with experimental observations, and that the rules are useful for structural elucidation of unknown compounds.

1. DIPTI S
M PHARMACY (PHARMACEUTICAL
ANALYSIS)
1 SEMESTER
DEPARTMENT OF
PHARMACEUTICAL CHEMISTRY
SRMC & RI (DU)
WOODWARD FIESER RULES
1

2. INTRODUCTION
• Robert Burns Woodward came up with a set
of rules in the year 1965 to determine the
lambda max value theoretically
• Later these rules were modified by Louis
Fieser in the year 1959.Here the lambda max
was calculated related to the degree of
substitution of the compound .
2

3. CHROMOPHORES AND AUXOCHROMES
 CHROMOPHORE :
A chromophore is a covalentently unsaturated
Group or compound responsible for absorption of
ultraviolet radiation .( Double bond is an
important feature of these groups).These
groups impart colour to the compound .
Some examples of chromophores include
Alkenes(R-C=C),
Ketones(R-C=O),Esters(RCOOR),
Amides(R-CONH2),Nitro(RNO2)
3

4. 4

5. AUXOCHROMES
 They are saturated groups having non
bonding electrons attached to the
chromophoric groups.These groups alter the
intensity as well as the wavelength at which
absorption of UV light takes place
 Some examples of auxochromes include
OH group(hyrdoxyl)
NH2 (amino)
S-CH3(mercapto group)
5

6. AUXOCHROMES SOLUBILIZING GROUPS
CH3 SO3- Na+
O-CH3 NH2+ Cl-
OH SO2-NH2+
NH2 O- Na+
NO2
SO3NA
6

7. WOOD WARD FIESER RULES
Woodward Fieser rules consists of three set of
rules they include
 Woodward Fieser rules for conjugated dienes
and polyenes
Woodward Fieser rules for alpha,Beta
unsaturated compounds
Woodward Fieser rules for aromatic
compounds and Benzoyl derevatives
7

8. RULES FOR CONJUGATED DIENES
AND POLYENES
 Each type of diene/triene have certain fixed
values at which absorption of UV light takes
place .They are the Base value or the parent
value
 In addition to this there are contributions
made by ring residues, double bond
extending conjugations and polar groups like
Cl, OH
8

9. TERMINOLOGIES USED
 HOMOANNULAR DIENE :
A homoannular diene is a cyclic diene having a
conjugated double bond in the same ring
Example : Benzene
9

10. HETEROANNULAR DIENE
These are cyclic dienes
having conjugated double
bonds in different ring
systems
10

11. ENDOCYCLIC DOUBLE BOND
 This includes double bond present within the
ring system
11

12. EXOCYCLIC DOUBLE BOND
 Double bond in which the doubly bond atom
is a part from the ring system (Double bond
outside the ring system).
12

13. In the above example Ring B has
one exocyclic double bond and
one endocyclic double bond
.where as ring A has only one
endocyclic double bond
13

14. PARENT VALUES FOR CONJUGATED
DIENES
Hetero annular diene 215nm
Homoannular diene 253 nm
Acyclic trienes 245nm
14

15. INCREMENTS
 Ring residues or alkyl group= 5nm
 Double bond extending conjugation=30 nm
 AUXOCHROMES
OR -6nm
SR -3nm
Cl,Br-5nm
OCH3-0nm
15

16. EXAMPLE :1
16

17. SOLUTION
 In the given example the parent value was
found to be 215 nm as it is a heterocyclic
diene
 It has 1 exocyclic double bonds so there is an
increment of 5nm
 It has 3 ring residues 3*5 =15
17

18. 18

19.  Hetero annular diene=215nm
 3 ring residues ie 3*5=15nm
 1 exocyclic double bond=5nm
Theoretically calculated value =
215+15+5=235nm
Practically observed value = 235nm
19

20. EXAMPLE :2
20

21. SOLUTION
Homo annular diene = 253 nm
2 Ring residues ie.2*5= 10 nm
2 Alkyl substituentsie ie 2*5 = 10 nm
Theoretically calculated value=273 nm
Practically observed value = 263 nm
21

22. EXAMPLE :3
22

23. SOLUTION
 Homo annular diene = 253nm
 2 Ring residues ie. 2*5 = 10nm
 2 Alkyl substituents ie 2*5 = 10 nm
 Theoretically calculated value = 240 nm
23

24. EXAMPLE 4
24

25. SOLUTION
 Hetero annular diene = 215nm
 4 ring residues ie. 4*5 = 20nm
 Theoretically calculated value = 235 nm
 Practically observed value = 236nm
25

26. 26

27. WOODWARD FIESER RULES FOR
ALPHA ,BETA UNSATURATED
CARBONYL COMPOUNDS
 Wood ward Fieser rules is extended to
calculate the lambda max of alpha, beta
unsaturated carbonyl compounds .There is a
base value to which the substituent's effects
can be calculated by using the following
formula.
 Λmax = Base value +substituent's value
+other substitutions
27

28. PARENTVALUES NANOMETRE
Alpha,beta unsaturated ,acyclic or
cyclic ketone
215 nm
Alpha , beta 5 membered ring 202nm
Alpha,beta unsaturated aldehyde 207nm
28

29. INCREMENTS
Alkyl substituent at alpha
position
10 nm
Alkyl substituent at beta
position
12 nm
Alkyl substituent at higher
positions
18nm
Exo cyclic double bond 5 nm
Double bond extending
conjugation
30 nm
Homo annular conjugated
diene
39 nm
29

30. EXAMPLE :5
SOLUTION :
Parent value for alpha ,beta unsaturated
acyclic ketone = 215 nm
1 alkyl substituent at alpha carbon=10nm
2 alkyl substituents at beta carbon=24nm
(12*2 = 24nm)
Theoretically observed value = 249 nm
30

31. EXAMPLE :6
SOLUTION
Base value = 215 nm
Double bond extending conjugation = 30 nm
Ring residue at delta position = 18 nm
Theoretically calculated value = 263 nm
Practically observed value = 253 nm 31

32. EXAMPLE :7
SOLUTION
Base value = 215 nm
2 ring residues at beta position = 24 nm
(2*12=24)
Theoretically calculated value =235 nm
32

33. WOOD WARD FIESER RULES FOR
AROMATIC AND BENZOYL
DEREVATIVES
33

34. EXAMPLE :8
SOLUTION
Base value = 246 nm
chlorine at para position = 10 nm
Calculated theoretical value= 256 nm
Practically observed value = 254 nm
34

35. EXAMPLE :9
SOLUTION
Base value = 246 nm
OH at meta position = 7 nm
OH at para position = 25 nm
Calculated value = 278 nm
Observed value = 281 nm 35

36. EXAMPLE :10
SOLUTION
Base value for esters/acids = 230 nm
Bromine at Para position = 15 nm
Theoretically observed value = 245 nm
36

37. ADVANTAGES OF WOODWARD
FIESER RULES
 This helps in determination of the
wavelength at which maximum absorption of
UV light takes place
 This is done by relating the position and
degree of substitution of the given compound
 In most cases the theoretically predicted
values are more over similar to he practically
determined values (+_ 5)
37

38. DISADVANTAGES OF WOODWARD
FIESER RULES
 Sometimes the theoretically observed value
has a large variation compared to the
practically obtained values
38

39. APPLICATIONS
 Used in the structural elucidation of various
compounds of unknown origin
 This helps in differentiating between
compounds whether they are cyclic, acyclic
or aromatic in nature due to the
determination of respective lambda max
values
39

40. REFERENCES
 A text book of Organic Spectroscopy by P.S
Kali ( pg :43)
 Y.R Sharma , A text book of Elementry
Organic spectroscopy ( pg 38 -46)
40