DFT/B3LYP study of O–H bond dissociation enthalpies of para and meta substituted phenols: Correlation with the phenolic C–O bond length

Determination of gas-phase acidities of dimethylphenols: Combined experimental and theoretical study

“…The same conclusion was also reached by Wright and coworkers [27]. In fact, several papers have reported the calculated gasphase structures of phenol as well as the structures of several monosubstituted phenols using different quality basis sets with success [28,29]. With a computational "low-cost" standard basis set, such as 6-31G(d), the average deviation of our calculated distances from the experimental data is very small (0.005 Å).…”

Theoretical study of the energetics of carboxylic O–H bond cleavage in the para- and meta-substituted benzoic acid derivatives

“…On the other hand, strong electron-withdrawing groups, such as CN, CF 3 , NO 2 and SO 2 Me, increase the BDE values by 4-5 kJ mol -1 . The studied substituents in the para position induce changes up to 13 kJ mol -1 , which are significantly less pronounced than those obtained for para-substituted phenols, where substituent induced changes in BDE were up to 58 kJ mol -1 (Klein and Lukeš, 2006b). Analogously, for meta-substituted phenols, the changes in BDEs up to 17 kJ mol -1 were observed, while for benzoic acid derivatives, the effect of substituents was considerably weaker, up to 8 kJ mol -1 .…”

“…For meta-substituted benzoic acids, the line slope value is larger though the two values can be considered similar with respect to their standard deviations. An opposite trend was observed for phenols (Klein and Lukeš 2006b). Moreover, both dependences were significantly steeper with the line slopes values of 36.7 (para) and 18.7 (meta).…”

“…not exceed 1 kJ mol -1 , which clearly demonstrates that the majority of the studied substituents exert practically the same effect on BDE in the two positions. Comparing BDEs found for benzoic acid derivatives with values obtained for para-and meta-substituted phenols (Klein and Lukeš, 2006b), homolytic cleavage of the phenolic O-H bond shows lower energy requirement. In phenols, gas phase BDEs in the range from 306 to 364 kJ mol -1 were observed and all values are lower than O-H BDEs of the carboxylic group in substituted benzoic acids.…”

Theoretical Study of Primary Antioxidant Action Thermodynamics

“…For para-and meta-substituted phenols (Klein and Lukeš 2006a, 2006b, 2006c, Klein et al 2009) and thiophenols (Rimarčík et al 2011, Rottmannová et al 2012, we have quantified the effect of various electron-donating and electron-withdrawing substituents on the enthalpies of the homolytic and heterolytic O-H and S-H bonds cleavage in the gas-and solution-phase. Usually, benzene and water were chosen as typical models of polar and non-polar solvent.…”