Paper Titles in Periodical
International Letters of Chemistry, Physics and Astronomy
Volume 14

Subscribe

Subscribe to our Newsletter and get informed about new publication regulary and special discounts for subscribers!

ILCPA > Volume 14 > Calculation of Diffusion Coefficients for...
< Back to Volume

Calculation of Diffusion Coefficients for Oxidation of Ferrocene Derivative Synthesized at Two Different Electrodes Using Rotating Disk Electrode (RDE)

Full Text PDF

Abstract:

The electrochemical behavior of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide synthesized is studied by Rotating Disk Electrode (RDE) Voltammetry to study the kinetics of oxidation and the effect of hydrazide group on ferrocene in organic medium. Thus, two different electrodes (Pt and Gc) were used in ordre to determine this latter. According to the ferrocene taken as a witness the hydrazide group related to the ferrocene made oxydation more difficult. This ferrocenic derivative showed an electrochemical stability, a reversible electrochemical system and an electronic attractor effect of these substitutional ferrocene groups. Finally, we calculated some electrochemical parameters which were: the diffusion coefficients (D), the layer thickness (δ) in addition to the electron transfer rate.

Info:

Periodical:
International Letters of Chemistry, Physics and Astronomy (Volume 14)
Pages:
39-47
Citation:
S. N. Nacer et al., "Calculation of Diffusion Coefficients for Oxidation of Ferrocene Derivative Synthesized at Two Different Electrodes Using Rotating Disk Electrode (RDE)", International Letters of Chemistry, Physics and Astronomy, Vol. 14, pp. 39-47, 2013
Online since:
Sep 2013
Export:
Distribution:
References:

[2] . EXPERIMENTAL.

[2] . 1. Chemicals All chemicals were of reagent grade and were used without further purification. Solvents were purified according to standard methods [7]. All reactions were conducted under nitrogen. Solutions were dried over anhydrous magnesium sulphate and evaporated under reduced pressure using a rotary evaporator. The electrolyte salt tetrabutylammonium tetrafluoroborate Bu4NBF4 (Fluka, electrochemical grade 99 % purity) was dried for 1 h at 105 °C before use. CH2Cl2 (Sigma–Aldrich, 99. 9 % purity) was dried over molecular sieves before use. Argon plunging tube bottle was provided by ENGI (Enterprise nationale des gaz industriels). All the freshly prepared solutions were degassed under argon gas flow before experiments.

DOI: https://doi.org/10.7554/elife.25217.008

[2] . 2. Instrument Electrochemical characterization was carried out on a potentiostat type voltalab 40 of radiometer, with a three-stand electrode cell. Cyclic voltammetric experiments were performed in deoxygenated CH2Cl2 solution of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide with respectively 10-1 M of Bu4NBF4 as supporting electrolyte and N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide concentration of 10-3 M. The three electrodes used were glassy carbon and Platinium disk as the working electrodes, saturated calomel electrode as a reference electrode, and Pt wire as an auxiliary electrode. The working electrode was polished with 0. 05 μm alumina slurry for 1–2 minutes, and then rinsed with double-distilled and deionized water. This cleaning process is done before each cyclic voltammetry experiment.

DOI: https://doi.org/10.4314/jfas.v3i2.9

[3] . RESULTS AND DISCUSSION.

[3] . 1. Synthesis (Ferrocenylmethyl)trimethylammonium iodide The salt was synthesized according to literature procedures [8].

[3] . 2. Synthesis N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide N'-Phenylbenzohydrazide was added to a well stirred solution of (Ferrocenylmethyl) trimethylammonium iodide in sodium-dried toluene. The resulting suspension was heated under reflux for 6 h. It was then allowed to cool to room temperature and filtered. The filtrate was washed with water to remove any trace of unchanged quaternary ammonium salt. It was then dried and evaporated. The residue was recrystallized from ethanol to give N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide as yellow-orange needles. The proton N.M.R. spectrum of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide shows eleven peaks at δ 4. 12(t, 2H, Hb); 4. 15(s, 5H, C5H5); 4. 19(t, 2H, Ha); 4. 60(s, 2H, CH2); 6. 86(t, 1H); 6. 95(d, 2H); 7. 26(t, 2H); 7. 42(m, 2H); 7. 53(t, 1H); 7. 62(s, 1H) and 7. 72ppm(m, 2H, C6H5 and NH). Figure 1. Figure 1. 1H. N.M. R spectrum of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide in CDCl3. The carbon N.M.R. spectrum also shows fourteen peaks, the first at 51. 20 ppm correspond to the carbon of the methylene group. The second at 68. 60, 69. 80, 77. 60 and 80. 10 ppm which correspond to the ten carbons of the ferrocene and the rest of the peaks at 113. 40, 119. 75, 127. 20, 128. 30, 129. 20, 132. 00, 132. 80 and 148. 80 correspond to the carbon of the phenyl group and finely at 167. 30 correspond to CO, Figure 2. Figure 2. 13C. N.M. R spectrum of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide in CDCl3. The methylene group of the salt N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide is characterised by its down orientation on the dept. spectrum, Figure 3. Figure 3. Dept spectrum of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide in CDCl3.

DOI: https://doi.org/10.4314/jfas.v3i2.9

[3] . 3. Electrochemical studies It is well known that N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide easily undergoes one electron oxidation to form ferrocenium cation in a reversible manner [9-10] Figure 4. Thus, we investigated the electrochemical N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide behaviors in aqueous media (ethanol/aq. H2SO4) [11]. In present work, we report electrochemical behavior of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide in organic medium on a classy carbon and platinum electrodes. Electrochemical behavior of FcX and FcX+ couple in both solutions was investigated by RDE. The N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide was synthesized according to literature procedures [7]. Figure 5, a shows RDE Polarogrammes for ferrocene and N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide at a series of rotation rates. It is evident from the data that the current generated by the RDE method is much larger than that generated under diffusion control. The much larger current that was obtained using RDE, reflects the efficiency of this method. Figure 4. Reversible mono electronic oxidation of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide. A B C A Figure 5 (A, B). Polarogramme of 1 mM Ferrocene and 100 mM Bu4NBF4 in CH2Cl2 (A) at glassy carbon working electrode (B) at platinium working electrode, Pt counter electrode, and CSE reference electrode at 0. 50 V·s-1 (Rotating rate 400, 600, 800, 1000 rpm). The diffusion current limit, the current half-wave and half-wave potential are calculated at different rotation speed of the two electrodes, Table 1. Table 1. Electrochemical parameters calculated from polarogammes obtained at glassy carbon and platinum electrodes of different rotational speed in organic medium. Electrode ω tour/min ilim µA/cm2 iP/2 µA/cm2 E1/2 mV Pt.

DOI: https://doi.org/10.4314/jfas.v3i2.9

[40] 0.

[14] . 76.

[7] . 38.

[50] 7. 5.

[20] [60] 0.

[17] . 87.

[8] . 93.

[51] 8.

[24] . 494.

[80] 0.

[20] . 25.

[10] . 125.

[52] 5. 5.

[28] . 284.

[10] 00.

[22] . 43.

[11] . 215.

[53] 3.

[31] . 622 GC.

[40] 0 ‏27. 58 ‏13. 79 ‏532.

[20] [60] 0 ‏34. 4 ‏17. ‏2 ‏543. 5.

[24] . 494.

[80] 0 ‏39. 5 ‏19. 75 ‏549. 5.

[28] . 284.

[10] 00 ‏42. 96 ‏21. 48 ‏550.

[31] . 622.

[3] . 4. Calculation of diffusion coefficient The Levich equation predicts the current observed at a rotating disk electrode and shows that the current is proportional to the square root of rotation speed. The equation is: (1) Where Dox: diffusion coefficient of the oxidant is expressed in cm2·s-1 ω: rotational speed of the electrode (rad·s-1) γ: kinematic viscosity in cm2·s-1 Kinematic viscosity: is the ratio of the viscosity on the density, we have for dichloromethane: viscosity = 0. 43 mPa·s 25 °C density d = 1. 328 The kinematic viscosity (≈ 10-6 m2·s-1, for an aqueous solution at 25 °C) The relationship between i and the square root of rotation speed (2) On another hand the limited current is given by, (3) Where as: n, number of electrons F: is the Faraday (9. 65·104 C/mol) A: is the area of the working electrode (cm2). D: is the coefficient diffusion (cm2·s-1) C: is the concentration (mol/cm3), in our case is equal to10-3 mol/l Replacing equations 2 and 3 in 4 gives, (4).

DOI: https://doi.org/10.1135/cccc19780535

[3] . 5. Applications For a rotating rate of the working electrode equal to 400 t/min., the coefficient diffusion of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide in dichlormethane is. The coefficient diffusion of ferrocene in aqueous ethanol is calculated as above. Table 2 summarize the obtained values. Table 2. Diffusion coefficients of compound calculated from polarogramme of Figure 5. Electrode compound D×10-6 cm2/s δ(nm) Pt ferrocene.

[19] , 21.

[12] 49, 21.

[3] [9] . 78.

[99] 4. 39 GC ferrocene.

[77] , 16.

[19] 62, 62.

[3] [25] . 9.

[13] 70. 05.

[4] . CONCLUSION Voltammetry analysis on a RDE of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide in an organic solution indicates that the electrochemical reaction of N'-Ferrocenylmethyl-N'-Phenylbenzohydrazide in the studied solution is a diffusion controlled process using two different electrodes. The layer thickness δ at ethe (GC) electrode was thicker than δ at the (Pt). The same was observed in the coefficient diffusion. This ferrocenic derivative showed an electrochemical stability, a reversible electrochemical system and an electronic attractor effect of these substitutional ferrocene groups. ACKNOWLEDGMENTS The authors gratefully acknowledge Mr A. Khelef Maitre assistant at The University of El Oued for his help and advice, and the Technical staff in the laboratory of VPRS for its support. References.

DOI: https://doi.org/10.4314/jfas.v3i2.9

[2] Neghmouche N. S., Khelef A., Lanez T., Res. J. Phar. Bio. Chem. 1(1) (2010) 76-84.

[3] Neghmouche N. S., Khelef A., Lanez T., J. Fun. App. Sci. 1(1) (2009) 23-30.

[4] Neghmouche N. S., Lanez T., International Letters of Chemistry, Physics and Astronomy.

[4] (2013) 37-45.

[5] Terki B., Chérifi N., Lanez T., Belaidi S., Asian J. Chem. 18(3) (2006).

[6] Morikita T., Yamamoto T., J. Organomet. Chem. 809 (2001) 637-639.

[7] Osgerby J. M., Pauson P. L., J. Chem. Soc. (1958) 642.

[8] Neghmouche N. S, Lanez T., International Letters of Chemistry, Physics and Astronomy.

[7] (1) (2013) 1-7.

[9] Eisele S., Schwarz M., Speiser B., Tittel C., Electrochim. Acta 51 (2006) 5304.

[10] Neghmouche N. S., Lanez T., International Letters of Chemistry, Physics and Astronomy 5 (2013) 76-85.

[11] A. Khelef, N. S. Neghmouche, T. Lanez, J. Fun. App. Sci. 3(2) (2011) 75-84. ( Received 21 April 2013; accepted 24 April 2013 ).

Show More Hide