MLFF-MD simulations with NMR DFT sampling, Fig. , demonstrate clearly that rapid chemical exchange between the carbonyl oxygen -B, and hydroxyl oxygen -C, pairs gives a much improved two-environment simulation (red) of the experimental spectrum (black). The symmetric proton hopping (Fig. ) produces a fast exchange average value of δ iso = 161 ppm, and, through electric field gradient (EFG) tensor averaging, a C Q = 7.0 MHz and η Q = 0.2 for this new 'dynamic hydroxyl' peak (see Table ). (For clarity, the nomenclature of a 'dynamic hydroxyl' refers to an oxygen environment that is in fast exchange between a hydroxyl and carbonyl site). Small motions of the non-exchanging carbonyl environment, A, leads to minor changes in parameters (see Table ).