Turns out your high school chemistry teacher was wrong: protons don't actually act the way the textbooks say they do in acid.
March 27, 2026
Original Paper
Complementary Eigen-Zundel Interpretation Reconciles Thermodynamics and Spectroscopy of Excess Protons in Aqueous HF Solutions
arXiv · 2603.25371
The Takeaway
For decades, it was taught that in hydrofluoric acid, protons are firmly bound to fluoride ions. New high-precision simulations reveal that the protons are actually 'dynamically shared' and constantly dancing between the acid and surrounding water molecules, fundamentally changing our microscopic understanding of acidity.
From the abstract
Aqueous solutions of HF and HCl behave very differently at intermediate concentrations: HCl dissociates completely, whereas HF remains only partially dissociated and forms bifluoride (HF$_2^-$). This should lead to different excess-proton spectra in HF and HCl solutions, in contrast to experimental reports. Using ab initio molecular dynamics, we show that in HF the proton is not firmly bound to F$^-$, as suggested by textbook chemistry, but dynamically shared with a hydrating water molecule. Thi