Re: Calculation of chemical reactivity

From: Stefan Seidler <ts # - at - # eeb04.cup.uni-muenchen.de>
Subject: Re: Calculation of chemical reactivity
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
 ---
 stefan.seidler AT cup.uni-muenchen.de