Dimerization of organic free radicals in solution. 1. Temperature dependent measurements

Spectrochim Acta A Mol Biomol Spectrosc. 2002 Apr;58(6):1219-26. doi: 10.1016/s1386-1425(01)00712-0.

Abstract

Dimerization enthalpies and equilibrium constants have been determined for the radical anion of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), the radical cations of N,N,N',N'-tetramethyl-p-phenylenediamine, N,N-dimethyl-p-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine, N,N,N',N'-tetraethyl-p-phenylenediamine, N,N-diethyl-p-phenylenediamine and N,N,N'-trimethyl-p-phenylenediamine. Neutral radicals investigated are 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and galvinoxyl. Solvent used was acetone, EtOH/Et2O-mixture (2:1 volume), propionitrile/butyronitrile-mixture (1:1 M) and dichloromethane. Measured dimerization enthalpies deltaHdim vary from -72.1 to -16.6 k/mol.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetone / chemistry
  • Benzhydryl Compounds / chemistry
  • Benzoquinones / chemistry*
  • Chemistry, Physical / methods*
  • Cyclic N-Oxides / chemistry
  • Dimerization
  • Electron Spin Resonance Spectroscopy / methods
  • Free Radicals
  • Methylene Chloride / chemistry
  • Models, Statistical
  • Nitriles / chemistry
  • Phenylenediamines / chemistry
  • Temperature
  • Tetramethylphenylenediamine / chemistry
  • Thermodynamics

Substances

  • Benzhydryl Compounds
  • Benzoquinones
  • Cyclic N-Oxides
  • Free Radicals
  • Nitriles
  • Phenylenediamines
  • Acetone
  • dichlorodicyanobenzoquinone
  • Methylene Chloride
  • propionitrile
  • N-butyronitrile
  • Tetramethylphenylenediamine
  • TEMPO
  • galvinoxyl