The values of ΔfHo298.15 and So298.15 of the radicals formed by the abstraction of H atom from the p‐Benzylphenol and Dimethyl Phthalate

Abstract

AbstractIn the present work, the thermochemical properties of the radicals (Yj), formed by abstraction of H atom from Dimethyl Phthalate (o‐Ph(C(O)OCH3)2) and p‐Benzylphenol (p‐PhCH2PhOH), are determined at the B3LYP/6‐311++G(d,p) (j = 1), M06‐2X/6‐311++G(d,p) (j = 2), and RO/CBS‐4 M (j = 3 and 4) levels of theory. Their calculated values of Ho298.15(Yj, CALC) are used for the determination of thermochemistry of atomization (ΔrHo298.15(Yj,CALC)atom) and homodesmotic (ΔrHo298.15((RYi)j,CALC)REAC) reactions of considered radicals. The reported calibration dependencies are used for the correction of calculated values and determination of the most consistent and accurate values of ΔfHo298.15 and ΔfGo298.15. It is found that o‐CH3OC(O)PhC(O)OCH2∙ (1C), p‐PhC∙HPhOH (1D) and p‐PhCH2PhO∙ (3D) are the most thermochemically stable structures. The intersection of reported 3SEj (= 3σj) intervals of ΔfHo298.15(1Cj,CORR)atom of atomization results the value of ΔfHo298.15(1C,CORR)MEAN = −405.1 ± 1.3 kJ/mol (±3SEY = 3σY), while, the most accurate values of ΔfHo298.15(1D and 3D,CORR)REACMEAN = 114.7 ± 0.4 and 135.8 ± 5 kJ/mol (± 3SEYREAC = 3σYREAC) are determined using the values ΔfHo298.15((RYi)j,CORR)REAC of homodesmotic reactions. The values of ΔfGo298.15, determined using the values of ΔfHo298.15 and So298.15 of these radicals, demonstrate that the exothermic reaction (17) HO2∙ + p‐PhCH2PhOH → H2O2 + p‐PhC∙HPhOH (–22.9 kJ/mol) is thermochemically more favorable than the reaction (19) HO2∙ + p‐PhCH2PhOH → H2O2 + p‐PhCH2PhO∙ (–1.8 kJ/mol). However, the value of kT(17) = 1.63 × 10–14(T/298.15)3.6e(‐6282/T), calculated using the VTST, is kinetically more favorable at elevated temperatures, while, the reaction (19) (kT(19) = 1.04×10–16(T/298.15)2.17e(–5207/T)) is more important at T < 200 K. The thermochemical properties of these radicals, as well as the calculated rate constants of their formation in reactions of HO2∙ radicals with p‐Benzylphenol, are reported for the first time.