Guanidinium solvents with exceptional hydrogen bond donating abilities.

Guanidinium chloride-based solvents have been prepared using deep eutectic solvent principles. Strong hydrogen-bond (H-bond) donating abilities are established based on a range of measures of solvent polarity, including a novel 31P NMR chemical shift method. The physical properties and origin of the strong H-bonding ability of these solvents have been explored.