Predicting melting points of quaternary ammonium ionic liquids

A melting point at or below ambient temperature is an essential property of ionic liquids being considered as non-volatile replacement solvents. Here we use the Quantitative Structure-Property Relationship (QSPR) method to correlate and predict the melting points of organic salts based on the quaternary ammonium cation. For a set of 75 tetraalkyl-ammonium bromides, a correlation with R-2 = 0.790 is created, and for a set of 34 (n-hydroxyalkyl)-trialkyl-ammonium bromides, two correlations are created with R-2 = 0.716 and R-2 = 0.766. Descriptors used in the correlations are analyzed to determine structural features that lower melting point, and melting points are predicted for salts that incorporate these features.