The values of Δ_fH^o_298.15 and S^o_298.15 of the radicals formed by the abstraction of H atom from the p‐Benzylphenol and Dimethyl Phthalate

Abstract

In the present work, the thermochemical properties of the radicals (Y j ), formed by abstraction of H atom from Dimethyl Phthalate (o-Ph(C(O)OCH 3 ) 2 ) and p-Benzylphenol (p-PhCH 2 PhOH), 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 H o 298.15 (Y j , CALC) are used for the determination of thermochemistry of atomization (Δ r H o 298.15 (Y j ,CALC) atom ) and homodesmotic (Δ r H o 298.15 ((R Yi ) 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 Δ f H o 298.15 and Δ f G o 298.15 . It is found that o-CH 3 OC(O)PhC(O)OCH 2 • (1C), p-PhC • HPhOH (1D) and p-PhCH 2 PhO • (3D) are the most thermochemically stable structures. The intersection of reported 3SE j (= 3σ j ) intervals of Δ f H o 298.15 (1C j ,CORR) atom of atomization results the value of Δ f H o 298.15 (1C,CORR) MEAN = −405.1 ± 1.3 kJ/mol (±3SE Y = 3σ Y ), while, the most accurate values of Δ f H o 298.15 (1D and 3D,CORR) REACMEAN = 114.7 ± 0.4 and 135.8 ± 5 kJ/mol (± 3SE YREAC = 3σ YREAC ) are determined using the values Δ f H o 298.15 ((R Yi ) j ,CORR) REAC of homodesmotic reactions. The values of Δ f G o 298.15 , determined using the values of Δ f H o 298.15 and S o 298.15 of these radicals, demonstrate that the exothermic reaction (17) HO 2 • + p-PhCH 2 PhOH → H 2 O 2 + p-PhC • HPhOH (-22.9 kJ/mol) is thermochemically more favorable than the reaction (19) HO 2 • + p-PhCH 2 PhOH → H 2 O 2 + p-PhCH 2 PhO • (-1.8 kJ/mol).However, the value of k T (17) = 1.63 × 10 -14 (T/298.15) 3.6 e (-6282/T) , calculated using the VTST, is kinetically more favorable at elevated temperatures, while, the reaction (19) (k T (19) = 1.04×10 -16 (T/298.15) 2.17 e (-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 HO 2 • radicals with p-Benzylphenol, are reported for the first time.

Mechanism and Thermochemistry of Radical Driven Partial Chain Oxidation of p‐Benzylphenol

“…On the contrary, the previously reported [12,13] thermochemical properties of structures 1C, 2C and 1D, determined using only their thermochemistry of atomization reactions, have evaluated by accounting the thermochemistry of homodesmotic reactions, the results of wB97XD, M08HX and MN15 calculations and the last versions of calibration dependencies. [14] Calculated thermochemical properties of these compounds (1A-1D), reported previously in, [5,6,12,13] as well as their uncertainties, corresponded to 2SE Y or 2SE YRHp (ffi2σ Y ), are presented in Table 2. The boldfaced values of Δ f H o (Y) are recommendation of this and previous work.…”

“…(where N and Nr are, respectively, the total numbers of reference atomization and homodesmotic reactions, considered in [5,6,14,18] ), determined using the literature (Δ ra H o (X n , TAB), Δ refRHj H o (TAB)) and theoretical (Δ ra H o (X n ) i , (Δ refRHj H o ) i ) values, calculated using the i-th QM approach (Equations 1 and 2) for the reference compounds (X n ) and homodesmotic reactions (refRH j ).…”

“…In the present study, the values of S o (Y) of considered compounds are determined using the results of B3LYP calculations (i = 2). [5] The values of S o (Y 2 , CALC), calculated using the B3LYP vibration frequencies, as well as the values of S o (Y 2 , CORR), determined using the corrected vibration frequencies, are reported in Table 8. The scaling factor (= 0.963), recommended in, [21] is used for the correction of vibration frequencies of all considered compounds excluding only structure 3D, formation of which is not supported by B3LYP and wB97XD calculations.…”

“…This compound is also considered as the component of surrogate bio-oil, imitated the physical and chemical properties of it solid and liquid fractions (tar, char). [4,5] Therefore, the mechanism of it oxidation and pyrolysis can be important part of development of technologies for the effective and deep conversion of bio-oils to gas phase products and/or fuels.…”

“…The thermochemical properties of p-penzylphenol (1A) and the radicals, formed by abstraction of H atom from them, are determined previously. [5,6] It is shown, the reaction (R1) of pbenzylphenol with radical (R * ), formed during the combustion of organic fuels:…”