[pfnm]

We added a solution of AgNO3 to ferrocene. Rapidly, a blue colour change occurred. This was the oxidation of ferrocene (which has a central Fe(II) ion) to ferrocenium (which has a central Fe(III) ion).
The Ag was reduced to Ag(s).

We added the same solution to acetylferrocene, and no reaction was observed.

This indicates that Ag(I) can oxidise ferrocene, but not acetylferrocene.

The standard reduction potential for the reaction Ag+ + e- -> Ag(s) is +0.80V (from Atkins Physical Chemistry).

The standard reduction potential for Ferrocene -> ferrocenium is +0.40V.

I cannot find the standard reduction potential for the oxidation of acetylferrocene, but can I say, it is likely to be higher than +0.80V?

[AWK]

http://imr.chem.binghamton.edu/labs/ferrocene/ferrocene.html

[pfnm]

Hi, thanks for that.

The website says:

A typical cyclic voltammogram of ferrocene showed a reversible oxidation at E1/2 = +0.35 V vs. Ag/AgCl...A typical cyclic voltammogram of acetylferrocene also showed a reversible oxidation at E1/2 = +0.58 V vs. Ag/AgCl...these results are comparable to the reported E of acetylferrocene at +0.27 V vs. the ferrocene/ferrocenium couple (6).

So if the reported E of acetylferrocene with respect to the ferrocene/ferrocenium couple is +0.27V, and the reported E of ferrocene with respect to Ag/AgCl is +0.35, does this mean the reported E of acetylferrocene with respect to Ag/AgCl would be +0.85V? (0.35V + 0.27V)?

I am trying to rationalise the observaton that AgNO3 oxidised Ferrocene to blue ferrocenium ions. But it did not produce a colour-change when added to acetylferrocene, leading us to believe that Ag(I) can oxidise ferrocene but not acetylferrocene.

The rxn Ag(I) + e- -> Ag(s) has an E value of +0.80V, which would be consistent with that, so long as acetylferrocene/acetylferrocenium couple has an E value of +0.85V, and ferrocene/ferrocenium has an E of +0.35V.