The Catalytic Effect of Fluoroalcohol Mixtures Depends on Domain Formation
O Holloczki and A Berkessel and J Mars and M Mezger and A Wiebe and SR Waldvogel and B Kirchner, ACS CATALYSIS, 7, 1846-1852 (2017).
In the present contribution, we investigated catalytically active mixtures of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and aqueous H2O2 by molecular dynamics simulations. It is clearly observable that the HFIP molecule strongly binds to the H2O2, which is necessary for the desired catalytic reaction to occur. Upon the addition of the substrate cyclooctene to the solution, this interaction is enhanced, which suggests that the catalytic activity is increased by the presence of the hydrocarbon. We could clearly observe the microheterogeneous structure of the mixture, which is the result of the separation of the hydroxyl groups, water, and H2O2 from the fluorinated alkyl moiety in the form of large domains, which span through large areas of the system. The hydrocarbon, however, does not fit into either one of these two microphases, and it forms separate aggregates in the macroscopically homogeneous liquid, creating thereby a triphilic mixture. The latter kinds of aggregates are mostly surrounded by the fluorous moieties, and therefore, the H2O2 has to move from the polar through the fluorous domain to be able to react with the cyclooctene. Accordingly, the present reaction should be described figuratively as a phase transfer or an interfacial reaction, rather than a homogeneous liquid-phase process.
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