A comparison of binding energy and metastable zone width for adipic acid with various additives

The binding energy of nine alkanoic acids to the major crystal faces of adipic acid were calculated employing molecular modelling techniques. The results indicate that the alkanoic acids bind strongly to the surface when compared to solvents and to adipic acid itself indicating that the alkanoic acids could be potential growth and nucleation inhibitors. The binding energies were found to increase with increasing carbon number to C14 to decrease from C14 to C16 and then to increase again. The effect of the alkanoic acids on the metastable zone width of adipic acid in ethanol solution were measured employing a differential scanning calorimeter. The results showed that each of the nine alkanoic acids increased the metastable zone width. The metastable zone widths were found to increase with increasing carbon number to C14 to decrease from C14 to C16 and to then increase again thus correlating well with the results obtained from binding energies. These results indicate that binding energy calculations appear to provide a valid method to screen impurities as potential nucleation inhibitors.