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

Abstract

The thermochemistry of radical driven chain oxidation of gaseous p‐benzylphenol is studied using the DFT (M062X,B3LYP,wB97XD,M08HX,MN15) approaches at 6‐311++G(d,p) level of theory. The values of ΔfHo(Y,MEAN) or ΔfHo(Yi,MEAN)RHp, used for the determination of ΔRxHo of considered reactions, are derived from the intersections of 3SEi intervals of values of ΔfHo(Yi,CORR) or ΔfHo(Yi,CORR)RHp, determined, respectively, using the corrected thermochemistry of atomization (ra) or homodesmotic (RHp) reactions. The linear calibration dependencies are used for the correction of their values of ΔraHo(Yi) and ΔRHpHo(Yi), derived from the calculated values of Ho.According to calculations, the most thermochemically favorable product is benzophenone,4‐ol (ΔfHo298.15(benzophenone,4‐ol)=−126.0±7.6(±2σ) kJ/mol), while, the formation of PhCHPhO (ΔfHo298.15=151.3±7.8 kJ/mol) and PhC(OH)PhO (ΔfHo298.15=39.6±6.5 kJ/mol) is thermochemically unfavorable. The formation of benzophenone,4‐ol is due the tautomerization or dissociation of O−O bond of PhC(O2•)HPhOH (ΔfHo298.15=47.9±4.8 kJ/mol), produced, respectively, OH or PhC(O•)HPhOH (ΔfHo298.15=53.0±7.1 kJ/mol) radicals. However, the formation of PhC(O2•)HPhOH is exoergic only at T<500 K.The formation of PhC(O2H)HPhOH (ΔfHo298.15=−104.2±5.9 kJ/mol) and PhC(OH)HPhOH (ΔfHo298.15=−177.8±5.3 kJ/mol) via transfer of H atom from p‐benzylphenol is also thermochemically favorable, but can only be important, respectively, at low (T<800 K) and at high T. In addition, the tautomerization of PhC(O⋅)HPhOH to PhC⋅ (OH)PhOH (ΔfHo298.15=−61.0±1.3 kJ/mol) is thermochemically favorable and slightly depends upon T.