Theoretical study of the low-barrier hydrogen bond in the hydrogen maleate anion in the gas phase: comparison with normal hydrogen bonds

Quantum mechanical and thermodynamic ab initio calculations were performed to characterize and compare the gas-phase properties of the intramolecular hydrogen bond in the maleic monoanion, otherwise known as hydrogen maleate anion, with hydrogen bonds in the monoanion of maleic monoamide. The results provided evidence concerning its status as a low-barrier hydrogen bond, one of which relates to the short distance between the hydrogen-donor and hydrogen-acceptor atoms.