What is it about?
The reactivity of organic acids on titania is important for many green chemistry applications. So, the behaviour of formic acid on titania surfaces has been intensely studied, but its acid proton has escaped the most accurate experiments so far. Now we show that the formic acid proton is shared between one oxygen from the formic acid molecule and one oxygen of the titania surface. At very low temperature, this is due to quantum effects, while, at room temperature, the proton is shuttling between the molecule and the surface. In both cases, proton sharing makes the acid proton "invisible" to experiments.
Photo by Marin Tulard on Unsplash
Why is it important?
We show that the surface of titania acts like a protecting group for the formic acid proton. How does this work? Because the proton is shared with the surface, it is difficult for other molecules to take it away! This protecting role of the surface could explain, for example, why carboxylic acids on titania, upon addition of amines, give high-value products (amides) at low costs for the environment.
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This page is a summary of: The case of HCOOH on (101) anatase TiO2
: where is the acid proton?, Angewandte Chemie International Edition, August 2019, Wiley, DOI: 10.1002/anie.201909283.
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