Determination of enthalpies of formation of organic free radicals from bond dissociation energies 2. Halosubstituted radicals

Abstract

The enthalpies of formation (AHf) for 23 halosubstituted radicals were determined from the published data on bond dissociation energies. The A/'/f values of the corresponding molecules necessary for the calculation of AHf ~ of the radicals were taken from handbooks or calculated by the additive-group method. The conjugation energies of the radicals are calculated, and the effect of substituents at the ~-system on these values was shown. Errors of determination of the AHf values of the radicals were estimated.

Experimental and computational studies of the thermal decomposition of halon 1211

“…The thermochemical data for species C 2 Cl 2 F 4 are available in the existing database (BURCAT) but there is a significant difference between data reported recently in the literature in comparison with those in older studies. Values of Δ H o f, 298 for C 2 Cl 2 F 4 were found to be −887.3 kJ mol −1 from the database, −925.2 kJ mol −1 from Orlov et al 47, −925.5 kJ mol −1 from Kolesov and Papina 48, and −923.6 kJ mol −1 from group additivity 43,49,50. The value of −925.2 from Orlov was adopted in our study.…”

“…The value of −925.2 from Orlov was adopted in our study. Value of Δ H ° f, 298 for C 2 Br 2 F 4 was obtained from Yaws 51 and Orlov et al 47 with values of −923.0 and −789.9 kJ mol −1 respectively. The value from Orlov et al was adopted as it is close to a value of −789.6 kJ mol −1 obtained from the group additivity theory.…”

Unimolecular Rate Constant and Threshold Energy for the HF Elimination from Chemically Activated CF3CHFCF3

“…We adopt Δ H f,298 ° (CF 3 CHF) = −166.7 kcal/mol, which is an average of four recent values (−168, −167.4, −166.7, and −164.5 kcal/mol) and correction to 0 K gives Δ H f,0 ° (CF 3 CHF) = −165 kcal/mol. Five reports (−371.1, −374.2, − 374.5, −370.6, and −365.6) for Δ H f,298 ° (CF 3 CHFCF 3 ) were averaged to give −371.2 kcal/mol and corrected to 0 K to give Δ H f,0 ° (CF 3 CHFCF 3 ) = −368.0 kcal/mol. The Δ H rxn,0 ° for reaction is −91.3 kcal/mol with a combined uncertainty of ±3 kcal/mol.…”

Modeling of combustion of fluorine-containing refrigerants

“…Table 2 lists the fluorine-containing hydrocarbon and oxidized-hydrocarbon species considered in the kinetic model with their standard enthalpies of formation ΔfH o , standard entropies So, and heat capacities at constant pressure Cp, o (all at 298.15 K). Thermochemical data for the species CF3CCF, CF=CHCF3, CHF=CCF3 and CH=CFCF3 were estimated using group additivity approaches, using several sources [7,[25][26][27][28][29][30][31]. Data for the other species were taken from the literature [27][28][29]32].…”