Mixture preparation. All chemicals used in this study are shown in Table in supporting information. They were purchased commercially from VWR, Sigma-Aldrich, Combi-Blocks, Chem-Impex and Tokyo Chemicals Inc. (TCI), and used without further purification. Chemicals were used within 1-2 days of receiving them or stored in a vacuum desiccator before use in mixture testing. Mixtures of HBA's and HBD's were added to wells in a 64-well plate in molar ratios (HBA:HBD) ranging from 1:6-12:1, although most mixtures were only evaluated a ratios from 1:2-3, with a total mass of 0.1 g. The well plate was placed in a Benchmark Incu-Shaker Mini incubator-shaker, shaken at 175 rpm and 55 °C for two hours. The samples in the well plate were observed to identify which mixtures were liquid, solid, or a combination. The well plate was allowed to cool to room temperature (20 °C), and once again observed within 30 minutes to identify which mixtures were liquid, solid or a combination. These observations were recorded into an accessible database. Many of the eutectic mixtures that were liquids in the well plates were also prepared in larger quantities, ~ 1-2 g, for further study. These mixtures were prepared by adding the correct molar ratios of hydrogen bond acceptor and hydrogen bond donor to a sample vial, and stirring under heat at temperatures < 60 °C until a homogeneous liquid was formed (typically less than 1 hour). Water content of the mixtures was measured by volumetric Karl-Fischer titration (Metroohm 870 KF Titrino Plus).