Thermolabile Kohlenwasserstoffe, 30 Thermische Stabilität und Bildungsenthalpie von 1,1,2,2- und 1,1,1,2-Tetraphenylethan. – Die Stabilisierungsenergien von Benzhydryl- und Triphenylmethyl-Radikalen

✍ Scribed by Beckhaus, Hans-Dieter ;Dogan, Barbara ;Schaetzer, Jürgen ;Hellmann, Siegrid ;Rüchardt, Christoph

• Publisher: Wiley (John Wiley & Sons)
• Year: 1990
• Tongue: English
• Weight: 871 KB
• Volume: 123
• Category: Article
• ISSN: 0009-2940
• DOI: 10.1002/cber.19901230126

✦ Synopsis

Energy of Stabilisation of Benzhydryl and Triphenylmethyl Radicals Heats of combustion of symmetrical (3) and unsymmetrical tetraphenylethane (4) were determined by combustion calorimetry: AH: (c) (3) = -3249.5 & 0.8; (4) = -3252.0 f 0.6 kcal/ mol. Enthalpies of sublimation of 3 (AHZuub,298K = 32.7 kcal/ mol) and 4 (31.7 kcal/mol) were obtained from vapour-pressure-temperature relations, which were determined by a gassaturation method. The resulting heats of formation AH? (g) (3) = 85.4 h 1.3 and AHP(g) (4) = 87.3 i 0.8 kcal/mol correspond to low strain energies: H, (3) = 1.5 and H, (4) = 4.6 kcal/ mol. The thermolysis reactions above 200°C in solution with thiophenol as a scavenger are clean first order processes. The following activation parameters are obtained from kinetic measurements: AH* (3) = 47.3 f 0.3, (4) = 45.0 f 0.3 kcal/ ' ' Standardabweichungen in Klammern. -b1 Temperatur, bei der die Halbwcrts7cit 1 h betrigt. -In Tctralin Thiophenol.df In Mesitylen 'Thiophenol. Resultate ohne Thiophenol-Zusatz s. Lit. '"'.