Subject: Re: Calculation of chemical reactivity

From: Stefan Seidler <[email-masked]>
Date: Mon, 31 Mar 2003 11:30:52 +0200 (MET DST)

> I was asked to investigate the relative reactivities of various aniline
> derivatives in the following reaction:
>
> Ph-NH2 -> Ph-NHOH -> Ph-NO
>
> where Ph are differently substituted Phenyl or Azaphenyl (Pyridine, Pyrimidine...) rings.
>

The reactivity of cmpds in redox reactions could be estimated by thermodynamic
considerations:  deltaG = nF(Udon - Uacc)              U: redox potential

For sure the oxidative reactions of organic cmpds include complex reaction
mechanisms, but the most important step in the mechanism of the oxidation
of aromatic amines is actually the electron transfer itself (no H
transfer, no O addition; see german "Organikum" D.6).
The redox potential is directly related to the energies of the frontier orbitals:
a substrate should be more easy oxidizeable the higher the energy of the HOMO.

Therefore the calculation of the HOMO energies might be useful for estimating
the reactivity and ordering your series.

Additional information regarding reactivity could be found in the bibliographies
of "synthesis planning tools" like EROS (Gasteiger) and CAMEO (Jorgensen).

Quantitative Prediction of Chemical Reactivity:
http://www2.chemie.uni-erlangen.de/publications/publ_topics/publ_topics-10.html

Regards,
   Stefan

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stefan.seidler AT cup.uni-muenchen.de