Hannover 2020 – scientific programme

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MO: Fachverband Molekülphysik

MO 5: MO Poster 1

MO 5.7: Poster

Monday, March 9, 2020, 17:00–19:00, Empore Lichthof

Hydrogen Atom Transfer (HAT) between phenol and phenoxy-radical — •Uwe Faltermeier and Bernhard Dick — Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Germany

Hydrogen Atom Transfer (HAT) reactions involving phenoxy radicals occur in various biological processes, like the breaking of free-radical chain reactions by tocopherol (Vitamin E). The self-exchange of a hydrogen atom between phenol and its corresponding phenoxy radical is the simplest-case scenario for such reactions. As such, it lends itself as calibration point for theoretical models. Despite its seemingly simple nature, almost no experimental data exists for this reaction. We present a method for determining the rate constant of this exchange and its thermal behavior by looking at the pseudo-self-exchange between phenol and phenol-d5. The radicals are produced by photolysis and the transient absorption of the samples in the µs range is recorded with a streak camera. Measurements at temperatures ranging from -5^∘ C to 35^∘ C yield rate constants for the exchange of ≈ 4 × 10⁵ s⁻¹ mol⁻¹. Reversing the direction of the exchange, from phenol to phenoxy-d5, we find the same rate constants. This shows that our system is a good approximation to the phenoxy/phenol self-exchange reaction.