WOODWARD_FIESER_RULES_CALCULATE_THE_λmax_-_PPT PRESENTATION .PDF

WOODWARD_FIESER_RULES_CALCULATE_THE_λmax_-_PPT PRESENTATION_B.PHARMACY "INSTRUMENTALS METHOD OF ANALYSIS" SUBJECT TOPICS, ALSO FOR NEET-PREPARED STUDENTS.

1. WOODWARD FIESER RULES,
CALCULATE THE λmax
NAME : KHALID HASAN
ROLL NO: 1590XXXXX
REG NO: 211590XXXXXXXX
SEC : A YEAR:4
th
COURSE:B.PHARMACY
SUBJECT : INSTRUMENTAL METHODS OF
ANALYSIS
SUBJECT CODE : PT 711

3. ❖CONTENT
I
➢INTRODUCTION.
➢WOODWARD- FIESER RULES.
➢WOODWARD - FIESER RULES FOR CONJUGATED DIENES.
➢WOODWARD - FIESER RULES FOR A,ẞ - UNSATURATED CARBONYL
COMPOUNDS.
➢WOODWARD - FIESER RULES FOR AROMATIC COMPOUNDS OR
BENZOYL DERIVATIVES.
➢REFERENCE

4. ❖INTRODUCTION
➢In 1945 Robert Burns Woodward gave certain rules for correlating
a structure. In 1959 Louis Frederick Fieser modified these rules
with more experimental data, and the modified rule is known as
Woodward and max for a given structure by relating the position
and degree of substitution of chromophore.

5. ❖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 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 basic
value to obtain λmax for a particular compound.
According to Woodward's rules the λmax of the molecule can be calculated using
a formula:
λmax = Base value + Σ substituent contribution + Σ Other Contributions
➢There are three sets of rules:
1.Woodward-Fieser rule for Conjugated dienes and polyenes.
2. For - unsaturated Carbonyl compounds.
3.For Aromatic compounds or Benzoyl derivatives.

6. ❖WOODWARD - FIESER RULE S
FOR CONJUGATED DIENES
Homoannular Diene:- Cyclic diene having conjugated double bonds in
same ring.
➢Heteroannular Diene:- Cyclic diene having conjugated double bonds in
different rings.

7. Endocyclic double bond:- Double bond present in a ring.
➢Exocyclic double bond: Double bond in which one of the
doubly bonded atoms is apart of a ring system. Here Ring A has
one exocyclic and endocyclic double bond. Ring B has only one
endocyclic double bond

8. ❑PARENT VALUES AND INCREMENTS FOR DIFFERENT
SUBSTITUENT OR GROUPS FOR CONJUGATED DIENES
Parent Value:
•Acyclic conjugated dienes and Hetero annular conjugated dienes λ 214 nm
•Homo annular conjugated dienes λ 253 nm
•Acyclic trienes λ 245 nm
➢Increments:
•Each alkyl substitute or ring residue λ+5 nm
•Exocyclic double bond λ+5 nm
•Double bond extending conjugation λ+30 nm
➢Auxochromes:
•-O-alkyl λ+6 nm
•-S-alkyl λ+30 nm
•-C1 ,- Br λ+5 nm
•-N(alkyl)2 λ+60 nm
•-OCOCH3 λ 0 nm

9. ❖EXAMPLES
1. Calculate absorption maximum in UV Spectrum of 2,4 Hexadiene.
▪Butadiene system; basic value = 217nm
▪2 Alkyl substituent(2X5nm) = 10nm
_________________________________________________________
✓Calculated value = 227 nm
✓Observed value = 227 nm

10. ❖WOODWARD FIESER RULE FOR ALPHA,
BETHA - UNSATURATER CARBONYL
COMPOUNDS
➢Woodward-Fieser rules can be extended to calculate the Amax of α,β-
unsaturated carbonyl compounds. there is base value to which the
substituent effects can be added and the Amax can be calculated using
the formula:
λmax = Base value + ∑ Substituent Contributions + ∑
Other Contributions
➢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

11. ❖PARENT VALUES AND INCREMENTS FOR DIFFERENT
SUBSTITUENT GROUPS FOR CARBONYL COMPOUNDS
Parent Value:
•α,B -unsaturated acyclic or six member edring ketone=215nm
•α,B -unsaturated five membered ring ketone =202 nm
•α,B -unsaturated aldehyde=207 nm Increments
➢Increments :
•Each alkyl substitute or ring residue at a position 10 nm
•At position B=12 nm
•At B position and higher position =18 nm
•Each Exocyclic double bond =5 nm
•Double bond extending conjugation= 30 nm
•Homo annular conjugated diene =39 nm

13. EXAMPLE

14. ❖WOODWARD - FIESER RULE FOR AROMATI
COMPOUNDS OR BENZOYL DERIVATIVES
❑PARENT VALUES AND INCREMENTS FOR BENZOYL DERIVATIVES
❖Parent Value:
X = alkyl / ring residue, ArCOR 246 nm
X = H ArCHO 250 nm
X = OH/O-alkyl, ArCO2H, ArCO2R 230 nm
❖Increments :
R = alkyl / ring residue o, m = 3nm , p = 10nm
R = OH/O-alkyl o, m = 7nm , p = 25 nm
R =NH2o, m = 23nm p = 58nm

17. ❖REFERENCES
Woodward, Robert Burns (1941). "Structure and the Absorption
Spectra of a,ẞ-Unsaturated Ketones". J. Am. Chem. Soc. 63(4):
1123.doi:10.1021/ja01849a066
A text book of organic spectroscopy by P.S Kalsi (page .no-40)
A text book of uv-visible and infrared spectroscopy by raja
shekaran (page no.88-100)
yr. sharma, elementary organic spectroscopy pg.no:36-48IUPAC
Gold Book heterocyclic compounds