Catalytic hydrogenation reaction of naringin-chalcone. Study of the electrochemical reaction

Article abstract of DOI:10.3390/50300589

The electrocatalytic hydrogenation reaction of naringin derivated chalcone is studied. The reaction is carried out with different catalysts in order to compare with the classic catalytic hydrogenation.

Full text of DOI:10.3390/50300589

589
Molecules 2000, 5
Catalytic Hydrogenation Reaction of Naringin-Chalcone. Study
of the Electrochemical Reaction
M. A. Nazareno, A. N. Giannuzzo, H. T. Mishima and B. A. López de Mishima
Instituto de Cs. Químicas. Facultad de Agronomía y Agroindustrias. U.N.S.E., Av. Belgrano (S) 1912.
(4200). Santiago del Estero, Argentina
E-mail: nazareno@unse.edu.ar
Abstract: The electrocatalytic hydrogenation reaction of naringin derivated chalcone is
studied. The reaction is carried out with different catalysts in order to compare with the clas-
sic catalytic hydrogenation.
Introduction
The electrocatalytic hydrogenation reaction of an unsaturated organic molecule involves mecha-
nisms implicating a hydrogen electroadsorption process and the adsorption of the substrate on the
catalyst surface [1]. The difficulties of the hydrogenation reactions result from the competence between
this reaction and the chemical or electrochemical desorption of the hydrogen. The electrocatalytic re-
action can be carried out in more moderate conditions of pressure and temperature compared with the
classic catalytic one [2]. Some electrochemical hydrogenation reactions of compounds such as aro-
matics molecules, alkenes and oils have been done using catalysts as Raney nickel, palladium, plati-
num and rhodium [3].
Naringin, a flavonoid extracted from the peel of some citric fruits and responsible for their bitter-
ness, is the precursor of dihydrochalcone compound. This kind of substances derived from flavonoids
presents a very intense sweet taste [4] therefore their synthesis become interesting because of their in-
dustrial potential as a sweetener.
OH
OH
OH
RO
OH
O
RO
O
O
RO
OH
O
[ H ]
HO-
H+
CH2
CH2
CH
CH
OH
OH
OH
Naringin
R=β-D-ramnosyl-(1,2)-D-Glucose
Chalcone
Dihydrochalcone

590
Molecules 2000, 5
Experimental
In order to study the reaction where the dihydrochalcone is formed, the experiences were carried out
in alkaline media (pH = 12) where the equilibrium between the flavanone and the chalcone is shifted to
the chalcone form. The position of this equilibrium was evaluated by UV-Vis absorption spectroscopy.
The electrochemical reductions were carried out in a glass with a two-compartment cell where working
electrode was separated from the counter electrode by a glass sinter. Platinum sheet was used as coun-
ter electrode and saturated calomel as reference separated by a bridge containing potasium hydroxide
solution. Different kinds of working electrodes were used: pure platinum sheet (geometric area 1 cm2),
a palladium-gold net and a carbon paste modified with PtO2 (geometric area 49 m2/g). The hydrogena-
tion reaction products were analyzed by UV-Vis absorption spectroscopy, HPLC and TLC.
Results and Discussion
Considering that the catalysts nature and their active area are very important, different catalysts
were studied. For initial studies of chalcone oxidation-reduction behavior a pure platinum electrode
was used. Current-potential curves were performed to analyze the electrochemical reactivity of chal-
cone solutions. The results show that there is no evidence of chalcone reaction in the potential region
of both hydrogen and oxygen evolutions. On the other hand, the adsorption of organic molecule on
platinum was also studied. The chalcone was adsorbed in the hydrogen electroadsorption potential
zone. These results show that reaction is possible.
The electrocatalytic hydrogenation reactions were performed at constant potential with PtO2 and
palladium-gold electrodes and the dihydrochalcone was obtained. The classic hydrogenation reaction
was also done using PtO2 as catalyst for comparing purposes of the yields. Although both results are
quite similar, work is in progress to further improve the efficiency of the process.
Acknowledgements: We thank Professor Paulo A. Bobbio for his advice. This work was supported by
the CICyT (UNSE) and A. N. G. acknowledges the receipt of a fellowship from CICyT (UNSE).
References and Notes
1. Mahdavi, B.; Marc Chapuzet, J.; Lessard J. Electrochim.Acta 1993, 38, 1377.
2. (a) Pintauro, P.N.; Phan, H.; Baizer, M.M.; Nobe, K. AIChE Symposium Series 1987, n°254, 83,
34; (b) Park, K.; Pintauro, P.N.; Baizer, M.M.; Nobe,K. J. Electrochem. Soc. 1985, 132, 1850.
3. Yusem, G.; Pintauro, P. N.; Cheng, P. C.; An, W. J. Appl. Electrochem. 1996, 26, 1779.
4. Horowitz, R. M.; Gentili, B. U. S. Patent 3.087.821, 1963. 3.890.296, 1975. 3.890.298, 1975.