Thermochemical properties of free radicals from G3MP2B3 calculations

For a set of 32 selected free radicals, energy minimum structures, harmonic vibrational wave numbers ω e , principal moments of inertia I A , I B , and I C , heat capacities C ° p ( T ), entropies S °( T ), thermal energy contents H °( T ) − H °(0), and standard enthalpies of formation Δ f H °( T ) were calculated at the G3MP2B3 level of theory in the temperature range 200–3000 K. In this article, thermodynamic functions at T = 298.15 K are presented and compared with recent experimental values. The mean absolute deviation between calculated and experimental Δ f H °(298.15) values resulted in 3.91 kJ mol −1 , which is close to the average experimental uncertainty of ± 3.55 kJ mol −1 . The influence of hindered rotation on thermodynamic functions is studied for isopropyl and tert ‐butyl radicals.