102001-98-9Relevant academic research and scientific papers
Thermolabile Hydrocarbons, 33. Thermochemistry and Thermal Decomposition of 9,9'-Bifluorenyl and 9,9'-Dimethyl-9,9'-bifluorenyl - The Stabilization Energy of 9-Fluorenyl Radicals
Rakus, Klaus,Verevkin, Sergej P.,Schaetzer, Juergen,Beckhaus, Hans-Dieter,Ruechardt, Christoph
, p. 1095 - 1104 (2007/10/02)
From thermochemical measurements the heats of formation ΔHf0(g) for fluorene (1), 9-methylfluorene (2), 9,9'-bifluorenyl (5), and 9,9'-dimethyl-9,9'-bifluorenyl (6) were determined.The homolytic cleavage of the dimers 5 and 6 to 9-fluorenyl (3) and 9-methyl-9-fluorenyl radicals (4), respectively, was studied in mesitylene with thiophenol as trapping agent and found to follow first-order kinetics.The activation parameters ΔH(excit.)(5) = 212.6 (+/-2.1) kJ mol-1, ΔS(excit.)(5) = 70.3 (+/-4.2) J mol-1 K-1, ΔH(excit.)(6) = 164.9 (+/-0.7) kJ mol-1, and ΔS(excit.)(6) = 88.2 (+/-1.9) J mol-1 K-1 were obtained.For 3 and 4 the radical stabilization energies RSE(3) = 67 (+/-7) kJ mol-1 (relative to isopropyl) and RSE(4) = 64 (+/-8) kJ mol-1 (relative to tert-butyl) were determined by a comparison with the activation parameters of the thermolysis of alkanes possessing the same strain enthalpy.The heats of formation for 3 and 4 and the C-H bond dissociation energies for the C-H bond in the 9-position of 1 and 2 were determined to be ΔHf0(g,3) = 300 kJ mol-1, ΔHf0(g,4) = 268 kJ mol-1, BDEC-H(1) = 343 and BDEC-H(2) = 338 kJ mol-1 (estimated errors correspond to those of the RSE values).A good correlation between the heats of vaporization of 37 aromatic hydrocarbons and their calculated solvent-accessible surfaces was demonstrated.Hence, a new method to estimate heats of vaporization was established. - Key Words: Heats of formation / Bond cleavage, C-C, kinetics of / Radicals, stability of / Correlation between heats of vaporization and solvent-accessible surfaces
