The document outlines the Woodward-Fieser rules developed for calculating the maximum wavelength (λmax) associated with molecular structures, with specific applications to conjugated dienes, α,β-unsaturated carbonyl compounds, and aromatic compounds. The rules provide a systematic method to determine λmax based on base values and substituent contributions. Additionally, it discusses various types of diene systems, their conformations, and how these factors influence UV absorption characteristics.

2. WOODWARD FIESER RULES
AND APPLICATIONS
Pharmaceutical Analysis

3. DECLERATION
• A TEXT BOOK OF ORGANIC SPECTROSCOPY BY
P.S KALSI (PAGE # 40).
• A TEXT BOOK OF UV-VISIBLE AND INFRARED
SPECTROSCOPY BY RAJASHEKARAN (PAGE # 88-
100).
• INTRODUCTION TO SPECTROSCOPY BY PAVIA
(PAGE # 590).

4. Table of Contents
• INTRODUCTION
• ADVANTAGES
• RULE FOR CONJUGATED DIENES
• RULE FOR CONJUGATED CARBONYL
COMPOUND
• RULE FOR ACYL BENZENES OR
AROMATIC COMPOUNDS
• APPLICATIONS

5. Introduction
In 1945 Robert Burns Woodward gave certain
rules for correlating λmax with molecular structure.
In 1959 Louis Frederick Fieser modified these
rules with more experimental data, and the
modified rule is known as Woodward-Fieser
Rules.
It is used to calculate the position and λmax for a
given structure by relating the position and degree
of substitution of chromophore.

6. • Each type of diene or triene system is having a certain fixed
value at which absorption takes place; this constitutes the
BASE VALUE OR PARENT VALUE.
• The contribution made by various alkyl substituents or ring
residue, double bond extending conjugation and polar groups
such as –Cl, -Br etc are added to t he basic value to obtain
λmax for a particular com pound.
WOODWARD- FIESER RULES

7. • It is used to calculate the position and
maximum wave length for a given structure.
• By relating the position and degree of
substitution of chromophore
ADVANTAGES

8. RULE FOR CONJUGATED DIENES
 Conjugated dienes and polyenes are found in
most organic compounds.
 Longer the conjugated system, greater the
wavelength of absorption maximum.
 According to Woodward’s rules the λmax of the
molecule can be calculated using a formula:
λmax = Base value + Σ Substituent
Contributions + Σ Other Contributions.

9. BaseValue
 Each type of diene or triene system is having a
certain fixed value at which absorption takes
place; this constitutes the Base value or
Parent value.
 The first step in predicting the wavelength of
maximum UV absorption for conjugated dienes is to
determine whether it lies in an s-trans or s-cis
conformation.

10. If it lies in the s-trans conformation, its
base wavelength is 217nm.
If it lies in the s-cis conformation, its
base wavelength is 253nm.

11.  the base value depends upon whether the
diene is a linear or hetero-annular or
transoid diene, or whether it is a cyclic or
homo-annular diene.
 The sum of all substituent contributions are
added to the base value to obtain the
wavelength of maximum absorption of the
molecule.

12. Woodward Fieser rule for
Conjugated Dienes and Polyenes
A)- Homoannular Diene:- Cyclic diene having conjugated double
bonds in same ring.
B)- Heteroannular Diene:- Cyclic diene having conjugated
double bonds in different rings.

13. C)-Endocyclic double bond:- Double bond present in a
ring.
D)- Exocyclic double bond: - Double bond in which one of the
doubly bonded atoms is a part of a ring system.

14. E)- Double bond extending :- When more double bonds are
present other than conjugations.

15. Parent values and increments for
different Substituents or Groups

16. Example of Woodward Fieser rule for
Conjugated Dienes and Polyenes

17. Example of Woodward Fieser rule for
Conjugated Dienes and Polyenes

18. Woodward Fieser rule for α,β -
unsaturated Carbonyl compounds
Woodward-Fieser rules can be extended to calculate
the λmax of α,β-unsaturated carbonyl compounds. In
a similar manner to Woodward rules for dienes
discussed previously, there is base value to which the
substituent effects can be added and the λmax can be
calculated using the formula:
λMAX = BASE VALUE + Σ SUBSTITUENT
CONTRIBUTIONS + Σ OTHER CONTRIBUTIONS

19. Following are a few sample applications of these rules. The
pertinent parts of the structures are shown in bold face.

20. Continue………

21. Continue………

22. Parent values and increments for
different Substituents or Groups

23. α,β-UNSATURATED ALDEHYDES,
ACIDS, AND ESTERS
• α,β -Unsaturated aldehydes generally follow the same
rules as enones except that their absorptions are
displaced by about 5 to 8 nm toward shorter
wavelength than those of the corresponding ketones.
• Nielsen developed a set of rules for α,β -unsaturated
acids and esters that are similar to those for enones

24. Examples:
• Consider 2-cyclohexenoic and 2-cycloheptenoic
acids as examples:

25. EMPIRICAL RULES

26. Woodward Fieser rule for Aromatic
compounds or Benzoyl derivatives.
The absorption that result from transitions within the
benzene chromophore can be quite complex. The
ultraviolet spectrum contains three absorption bands,
which sometimes contain a great deal of fine structure.
The electronic transitions are basically of the ∏ ∏*
type.

27. Parent values and increments for
Benzoyl Derivatives