Dimerization of organic free radicals in solution. 1. Temperature dependent measurements.
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.
Grampp
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G
Institute of Physical and Theoretical Chemistry, Graz University of Technology, Austria. grampp@ptc.tu-graz.ac.at
Landgraf
S
S
Rasmussen
K
K
Strauss
S
S
D000096:Acetone / Q000737:chemistry; D001559:Benzhydryl Compounds / Q000737:chemistry; D016227:Benzoquinones / Q000737:chemistry*; D002627:Chemistry, Physical / Q000379:methods*; D003497:Cyclic N-Oxides / Q000737:chemistry; D019281:Dimerization; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005609:Free Radicals; D008752:Methylene Chloride / Q000737:chemistry; D015233:Models, Statistical; D009570:Nitriles / Q000737:chemistry; D010655:Phenylenediamines / Q000737:chemistry; D013696:Temperature; D013772:Tetramethylphenylenediamine / Q000737:chemistry; D013816:Thermodynamics
D001559:Benzhydryl Compounds; D016227:Benzoquinones; D003497:Cyclic N-Oxides; D005609:Free Radicals; D009570:Nitriles; D010655:Phenylenediamines; D000096:Acetone; C000928:dichlorodicyanobenzoquinone; D008752:Methylene Chloride; C005557:propionitrile; C032723:N-butyronitrile; D013772:Tetramethylphenylenediamine; C003959:TEMPO; C020338:galvinoxyl