Calculation of lambda max for the compounds

1. APPLICATION OF WOODWARD
FIESER RULES IN STRUCTURAL
ELUCIDATION OF ORGANIC
COMPOUNDS
By
CH.LAKSHMI KALYANI
Y14MPH432
M.PHARMACY(PHARMACEUTICAL
ANYALSIS)
CHALAPATHI INSTITUTE OF
PHARMACEUTICAL SCIENCES

2. OBJECTIVES:-
• To familiraze the Woodward fieser rules
•To calculate the maximum wavelength of
organic compound.

3. INTRODUCTION:-
In 1945 Robert burn woodward gave certain
rules for correlating maximum wavelength
with molecular structure.
In 1959 luis fedrick fieser modified this rules
with more experimental data and modified
rules known as woodward fieser rules

4. ADVANTGE:-
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

5. TERMINOLOGY:-
 Conjugated diene:-organic compound
contaning two or more double bonds each
separated from other by a single bond
 Dienes:-it is also known as a alkadiene,
diolefin .
 It is one class of organic compound
contaning two ethyelnic linkages (carbon to
carbon double bond)

6. WOODWARD FIESER RULE
 It mean each type of diene or triene system
is having a certain fixed values at which
abosrption 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 the base
value to obtain for a particular
compound

7. BASIC INTRODUCTION:-
 HOMOANNULAR:- cyclic diene having
conjugated double bonds in same ring.
 HETEROANNULAR:-cyclic diene having
conjugated double bonds in different rings

8. BASIC INFORMATION REGARDING
CALCULATION OF MAXIMUM WAVE LENGTH OF
A COMPOUND
ENDOCYCLIC DOUBLE BOND:-double bond
present in a ring.
EXOCYCLIC DOUBLE BOND:-double bond in
which one of the doubly bonded atoms is a part
of ring system.
Here ring B has one exocyclic and endocyclic
double bond .ring A has only one endocyclic
double bond

9. PARENT VALUES AND INCREMENTS FOR
DIFFERENT SUBSTITUENTS/GROUPS FOR
CALULATING MAXIMUM WAVELENGTH
Conjugated diene correlation:-
a. Base value for homoannular diene=253nm
b. Base value for heteroannular diene=214nm
c. Alkylsubstituent to ring residue attached to the
parent diene =5nm
d. Double bond extending conjugation=30nm
e. Exocyclic double bonds=5nm

10. Hetero atoms:-
 -OR = +6nm
 - Cl =+5nm
 -Br = +5nm
 Example:- Base value = 214
nm
Ring residue = 3 x 5 = 15 nm
Exocyclic double bond = 1x 5 = 5 nm
λmax = 214 + 15 + 5 = 234
nm

11. EXAMPLE
Acyclic conjugated diene= 217 nm
2 alkyl substituents (2x5) = 10
nm
__________
λmax = 227 nm

12. APPLICATION OF WOODWARD
FIESER RULE FOR ALPHA,BETA
UNSATURATED
COMPOUNDS(ENONES)
 In this alpha, beta unsaturated compounds
the compound may be a aldehydes or
ketones.
 It may be acyclic or 6 membered or 5
membered ring systems

13. BASE VALUES FOR DIFFERENT
FUNCTIONAL GROUPS:-
KETONES
 If it is a acyclic compound =215nm
 If 6 membered ring system =215 nm
 If 5 membered ring system =202 nm
ALDEHYDES
 If it is a acyclic compound =210 nm
 If 6 membered ring system =215 nm
 If 5 membered ring system =202nm
CARBOXYLICACID AND ESTER
 If compound is carboxylicacid or ester =197nm

14. Values for substituents or
groups
 Double bond extended conjugation
=30nm
 Exocyclic double bonds = 5nm
 Homodiene compound=39nm

15. Group
Alkyl R 10 nm 12 nm 18 nm 18 nm
Alkoxy OR 35 nm 30 nm 17 nm 31 nm
Hydroxyl OH 35 nm 30 nm 30 nm 50 nm
Chlorine -Cl 15 nm 12 nm 12 nm 12 nm
Bromine –Br 25 nm 30 nm 25 nm 25 nm

16. example
Base value = 214 nm
β- Substituents = 1 x 12 = 12 nm
δ- Substituents = 1 x 18 = 18 nm
Double bond extending
Conjugation =1 x 30 = 30 nm
Exocyclic double bond = 5 nm
λmax = 279 nm

17. example
Parent conjugated enone
in acyclic compound = 215 nm
2 alkyl residue at position = 24 nm
λmax = 239 nm

18. example
Parent conjugated enone in six
membered ring = 215 nm
Substitution of alkyl groups at
position = 10 nm
Substitution of alkyl residue at
position = 12 nm
λmax = 237 nm

19. APPLICATION OF WOODWARDFIESER
RULE FOR AROMATIC COMPOUNDS
1.BASE VALUES :-
 Ar COR=246nm
 Ar CHO=250nm
 Ar CO2H=230nm
 Ar CO2R=230nm
 Alkyl groups or ring residues in ortho and meta
positions=3nm
 Alkyl groups or ring residue in Para
position=10nm

20. Values for substituents or
groups
Groups Ortho position nm Meta position nm Para position nm
-OH 7 7 25
-OCH3 7 7 25
-O 11 20 78
-Cl 0 0 10
-Br 2 2 15
-NH2 13 13 58

21. example
base value = 246 nm
Hydroxy group at meta position = 07 nm
Hydroxy group at para position = 25 nm
λmax = 278 nm

22. example
Base value =246
nm
Ring residue = 03 nm
OCH3 group at meta position = 07 nm
λmax = 256 nm

23. Fieser- kuhn rule
In the number of conjugated double bonds is more
than 4, the woodward and fieser rules may not be
applicable and hence fieser with kuhn has derived
an equation for predicting the λmax
λmax= 114+5M+n(48.0-1.7n)-16.5 Rendo-10 Rexo
M= no. of alkyl substitutents
N = no. of conjugated double bonds
Rendo= no. of rings with endocyclic bonds
Rexo= no. of rings with exocyclic bonds

24. example
No. of alkyl substituent's = 10
No. of rings with endocyclic double bond=2
λmax= 114+5x10+11(48-1.7x11)-(16.5x2)-(10x0)=453.3 nm

25. example
no. of alkyl substituents =8
No. of conjugated double bonds =11
λmax =114+5(8)+11[(48-1.7(11)]-0-0=476 nm

26. POINTS TO REMEMBER:-
 Incase for which both types of diene systems
are present then the one with the longer
wavelength is designated as a parent system
 When ever there is a increasing conjugation
leads to increase in wavelength and required
less amount of energy
 Up to four conjugations woodward fieser rule is
applied
 > four conjugation we have to use fieser khun
rule is applied.

27. REFRENCES
 A TEXT BOOK OF ORGANIC
SPECTROSCOPY BY P.S KALSI( PAGE
.NO-40)
 A TEXT BOOK OF UV-VISIBLE AND
INFRARED SPECTROSCOPY BY
RAJASHEKARAN( PAGE NO.88-100)