This document discusses the structural elucidation of flavonoids, flavones, and flavonols. Flavonoids contain 15 carbon atoms and consist of two benzene rings joined by a three carbon chain. Flavones do not contain hydroxyl groups, and when fused with alkali degrade into a phenol and aromatic acids. Flavonols contain one hydroxyl group, and when boiled with potassium hydroxide yield o-hydroxybenzoyl methanol and benzoic acid, indicating the structure is 3-hydroxy flavone. The proposed structures are then proven through synthesis methods like Robinson's method.

1. GENERAL STRUCTURAL
ELUCIDATION OF
FLAVONOIDS
Presented By:
Praveen Parkali
M.Pharm
Dept. Pharmaceutical Chemistry
JSS College of Pharmacy, Mysore.
Presented To:
Dr. Jaishree
Dept. Pharmaceutical Chemistry
JSS College of Pharmacy, Mysore.

2. Flavonoids are Polyphenolic
compounds possessing 15
carbon atoms; two benzene
rings joined by a linear three
carbon chain.
They are also known as
Anthoxanthins.
They are wiedely
distributed as
yellow pigments in
plants.

3. ELUCIDATION OF FLAVONES
 Molecular formulae: Using analytical Data
 Nature of oxygen atom: The no. of OH group is estimated
by the usual methods => Flavone does not contain any–
OH group.
 On fusion with alkali, flavones are degraded to a phenol
and aromatic acids. Ex:-

4.  Flavones on boiling with KOH gives four different products.
KOH
o-
hydroxydibenzoylmethane
Flavone

5.  Finally the structure proposed by degradation method is
proved by it synthesis.
i) Robinson’s method:
o-
hydroxydibenzoylmethan
e

6. ii) Baker-Venkatramans Method:
Na2CO3
HCl
flavones
PhCOCl
1:3-diketone

7. ELUCIDATION OF FLAVONOLS
 Same manner as that of flavone
 The mol formula is C15H10O3
 It contains one hydroxyl group as indicated by usual
methods.
 On boil with ethanolic solution of KOH, Flavonol yields ,o-
Hydroxybenzoyl methanol and benzoic acid indicates that
Flavonol is 3-hydroxy flavone.

8. Benzoic acid

9. Finally the structure of flavonols are confirmed by its synthesis
i) Robinsons method:
ω-methoxy-2-
hydroxyacetophen
one
Benzoic
anhydride
HI