Woodward's rules

1. BY
P.PAVITHRA
M.Pharm I Year

2. WOODWARD-FIESER RULES
 In 1945, Robert Burns Woodward gave
certain rules for correlating wavelength with
the molecular structure.
 In 1959, Louis Frederick Fieser modified
these rules with more experimental data and
the modified rule is known as
WOODWARD-FIESER RULES.
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3. ADVANTAGE
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4. WOODWARD–FIESER RULES
 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
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5. WOODWARD–FIESER RULES
FOR CONJUGATED DIENES
 Homoannular Diene
 Heteroannular Diene
 Endocyclic Double bond
 Exocyclic Double bond
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10. BASE VALUES FOR DIFFERENT FUNCTIONAL GROUPS
PARENT VALUE
Acyclic conjugated dienes and Heteroannular
conjugated dienes
215 nm
Homoannular conjugated dienes 253 nm
Conjugated trienes 246 nm
INCREMENTS
Alkyl substituent or ring residues 5 nm
Exocyclic double bond 5 nm
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11. AUXOCHROMES
-OR 6 nm
-SR 30 nm
-Cl,--Br 5 nm
-NR2 60 nm
-COCH3 0 nm
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12. GROUP alpha beta gamma delta
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
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13. GROUPS Ortho position Meta position Para position
-OH 7nm 7nm 25nm
-OCH3 7nm 7nm 25nm
-O 11nm 20nm 78nm
-Cl 0 nm 0nm 10nm
-Br 2nm 2nm 15nm
-NH2 13nm 13nm 58nm
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31. Example No:5
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32. Example No:6
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33. Example No:7
BASE VALUE=215 nm
2 Ring residues-2*5=10nm
 Calculated value=225nm
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34. Example No:8
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35. Example No:9
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36. Example No:10
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37. FIESER-KUHN RULE
 If the number of conjugated dienes is more than 4, the
Woodward-Fieser rules may not be applicable and
hence Fieser with Kuhn has derived a formula for
predicting the maximum absorbance at a particular
wavelength i.e.,
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38. FIESER –KUHN RULE
Example No:1
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39. Example No:2
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40. APPLICATION:
 Detection of conjugation:
It helps to show the relationship
between the different groups particularly with respect
to conjugation ; it may be between two or more
carbon –carbon double bond,between carbon –
carbon and carbon –oxygen double bond or between
double bond or aromatic ring.
 Determination of geometrical isomers:
Trans isomers exhibit maximum
wavelength at slightly longer wavelength.And have
larger extinction co-efficient than cis- isomers.
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41.  Detection of functional groups:
 Identification of unknown compound:
 Examination of polynuclear hydrocarbons.
 Identification of compound in different solvent.
 Determination of strength of hydrogen bonding.
 Elucidation of the structure of vitamin A and K.
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42. QUESTIONS ?
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BASE VALUE
 Acyclic conjugated dienes=215nm
 Exocyclic Double bond =5nm
 2 Ring residues-2*5=10 nm

43. REFERENCES:
 Organic Spectroscopy-William Kemp
 Spectroscopy of Organic Compounds-P.S.Kalsi
 Instrumental methods of Analysis-N.Gray
M.Calvin S.C.Bhatia
 Introduction to Instrumental Analysis –Robert
D.Braun
 Organic Analytical Chemistry –Jag Mohan
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