Cyclic Voltammetry: Meaning & Lab Results

[gravenewworld]

I'm trying to do this ferrocene lab, and we did cyclic voltammetry on our purified product and I calculated these results:


E_1/2= 664.6 mV
I_pc/I_pa=-.6221
Delta Ep=29.2 mV

Can anyone tell me what these numbers mean? I don't really understand what voltammetry tells you about your compound.

 

[chem_tr]

Hello, I've found http://materials.binghamton.edu/labs/ferrocene/ferrocene.html for your evaluation. In here, it reads the following:

The electrochemistry component of this laboratory was the first time that most students were exposed to cyclic voltammetry and the bulk electrolysis technique. An Amel System 5000 Potentiostat was used for all measurements. For cyclic voltammetry, the electrochemical cell was a 100 mL beaker equipped with a Ag/AgCl reference electrode (student prepared), a BAS (West Lafayette, IN) platinum-disk working electrode (2 mm diameter) and a large (1 cm2) platinum flag counter electrode. After having verified a flat background of tetrabutylammonium hexafluorophosphate (0.01 M) supporting electrolyte in acetonitrile in the range 0.0 to 1.0 V vs. Ag/AgCl, cyclic voltammograms of ferrocene and acetylferrocene (approximately 3.2 x 10-3 M) were obtained at scan rates of 100 500 mV/sec. A typical cyclic voltammogram of ferrocene showed a reversible oxidation at E1/2 = +0.35 V vs. Ag/AgCl with Ep/2 = 0.057V. A typical cyclic voltammogram of acetylferrocene also showed a reversible oxidation at E1/2 = +0.58 V vs. Ag/AgCl with Ep/2 = 0.044V. Small peaks for ferrocene were also visible in the acetylferrocene cyclic voltammogram. These results are comparable to the reported E of acetylferrocene at +0.27 V vs. the ferrocene/ferrocenium couple (6).

A second new electrochemical component that was recently introduced into this laboratory is the bulk electrolysis of ferrocene to ferrocenium. The electrochemical cell was a 100 mL beaker equipped with an Ag/AgCl reference electrode (student prepared), a BAS (West Lafayette, IN) reticulated vitreous carbon (RVC) working electrode and an extremely large platinum flag counter electrode. After having verified a flat background of tetrabutylammonium hexafluorophosphate (0.01 M) supporting electrolyte in acetonitrile in the range 0.0 to 1.0 V vs. Ag/AgCl, the bulk electrolysis of ferrocene (approximately 7.5 x 10-4 M) was achieved on several occasions. As expected, a new peak in the UV-Vis was observed at 620 nm and the solution changed color from orange to blue. Unfortunately to date, these experimental conditions are not reproducible.

Regards, chem_tr

 

[gravenewworld]

Hey thanks a lot I appreciate your help. Can I just ask 1 more question? When comparing cobaltocene with nickelocene which would be more reactive? I know that Cobaltocene has a 19 e- count and nickelocene a 20 e- count. Both would like to get to a stable 18 e- count. So would Cobaltocene be more reactive since it only has to get rid of 1 e- or would nickelocene be more reactive?

 

[chem_tr]

I think nickelocene would be more reactive, since it has to get rid of two electrons to reach the stable 18 electron configuration as soon as possible. However in another viewpoint, giving two electrons requires higher energy than giving only one electron as evidenced with alkali and Earth alkali metal ions.

You may want to check this website for useful information. Your textbooks should give some hints about the stability. Ferrocene is more stable I know it, but I think stability decreases with increasing electron count from 18.