When FeCl2/FeCl3 is added to chalcones, a reddish-brown colour appears, however, the equations for this reaction reported in the literature always show the chalcone as a charge balancing ion, rather than a ligand coordinated to the metal centre. So, what type of interaction exists in this case between Fe and the chalcone? Is it ionic or a coordinate bond?
Dear Mohammed,
Chalcones are open analogues of flavonoids and give bright red to purple colours with different reagents which can be used to distinguish them from other flavonoids such as flavanones, flavones, aurones etc. Studies show that the bathochromic shift arises due to the formation of carbonium ion at the carbonyl group (>C = O) of the chromogen (ArCOCH = CHAr) as an intermediate which produces deeper colour during the reaction.
Chemistry of the colour tests for chalcones with different reagents.
The commonly used reagents for colour tests of chalcones are (1) Alcoholic Ferric Chloride, (2) Concentrated sulfuric acid, (3) Sulfuric acid-Nitric acid, (4) Sulfuric acid-Acetic anhydride, (5)Sodium Borohydride and HCl acid, (6) Wilson’s boric test
and (7) Antimony pentachloride.
Alcoholic ferric chloride test
This test is applicable to only hydroxy chalcones and is fact the characteristic of phenolic group and is due to the formation of complex iron salt4. The nature of the colour developed have however a definite relation with the orientation of
the phenolic–OH in the chalcone molecule.
Find in attach, the full article : Colour reactions of chalcones and their mechanism (A Review)
Best wishes
Dear Mohammed,
Find in attach, a review article on:
A comprehensive review of the oxidative cyclisation of 2’-hydroxychalcones to aurones and flavones.
They showed inside: The using of FeCl3 in cyclisation of hydroxy chalcones to aurones and flavones.
Dear Mohammed,
Find in attach, Supplementary Material for Chemical Communications
This journal is © The Royal Society of Chemistry 2003
Electronic supplementary information entitled " Efficient and Inexpensive Catalyst System for the Aza-Michael Reactions of Enones with Carbamates"
You find inside:
UV analysis of the
CH2Cl2 or CH3CN solution of chalcone with this catalytic system (Me3SiCl and FeCl3·6H2O) to
confirm the possibility in the present reaction system. On the other hand, UV analysis of the
interaction of enones and Brønsted acid (aq. HBF4 ), Transition metal salts ( Cu(OTf)2, PdCl2)
were also be performed. These results showed in figure 1 and figure 2.
Figure 1:
In CH2Cl2, 1# the solution of chalcone; 2# the solution of chalcone and FeCl3·6H2O; 3# the solution of chalcone, Me3SiCl and FeCl3·6H2O.
Figure 2:
In CH3CN,4# the solution of chalcone and aq. HBF4; 5# the solution of chalcone and Cu(OTf)2;
6# the solution of chalcone and PdCl2(CH3CN)2; 7# the solution of chalcone, Me3SiCl and
FeCl3·6H2O.
Dear Mohammed,
Find in attach, Supplementary Material for Chemical Communications
This journal is © The Royal Society of Chemistry 2003
Electronic supplementary information entitled " Efficient and Inexpensive Catalyst System for the Aza-Michael Reactions of Enones with Carbamates"
You find inside:
UV analysis of the
CH2Cl2 or CH3CN solution of chalcone with this catalytic system (Me3SiCl and FeCl3·6H2O) to
confirm the possibility in the present reaction system. On the other hand, UV analysis of the
interaction of enones and Brønsted acid (aq. HBF4 ), Transition metal salts ( Cu(OTf)2, PdCl2)
were also be performed. These results showed in figure 1 and figure 2.
Figure 1:
In CH2Cl2, 1# the solution of chalcone; 2# the solution of chalcone and FeCl3·6H2O; 3# the solution of chalcone, Me3SiCl and FeCl3·6H2O.
Figure 2:
In CH3CN,4# the solution of chalcone and aq. HBF4; 5# the solution of chalcone and Cu(OTf)2;
6# the solution of chalcone and PdCl2(CH3CN)2; 7# the solution of chalcone, Me3SiCl and
FeCl3·6H2O.
Reaction of chalcones with FeCl3. What is the structure of the resulting complex? - ResearchGate. Available from: https://www.researchgate.net/post/Reaction_of_chalcones_with_FeCl3_What_is_the_structure_of_the_resulting_complex#57cd58d55b4952a6ef4e8183 [accessed Sep 5, 2016].
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