Applicability of DFTB+ Method for the Calculations of O–H Bond Dissociation Enthalpies of Phenols
Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, SK-812 37 Bratislava, Slovak Republic
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Abstract: In this work, O–H bond dissociation enthalpies (BDE) of non-substituted phenol and 26 meta- and para-substituted phenols were calculated using semiempirical DFTB+ method. In comparison with available experimental BDE values, calculated BDEs are overestimated by ca 40 kJ mol–1. DFTB+ method predicts lower substituent induced changes in BDE in comparison with experimental values. On the other hand, the found changes in O–H BDEs are in accordance with computationally significantly more demanding DFT/B3LYP/6-311++G** method. Obtained results show that DFTB+ method may be successfully employed for the fast estimation of substituent induced changes in phenolic O–H bond dissociation enthalpies.
Keywords: BDE, Hydrogen Atom Transfer Mechanism, Substituent effect, Antioxidant
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Acta Chimica Slovaca, Vol. 3, No. 2, 2010, pp. 12—19