The main objective of the study was to investigate the phase transition properties (melting temperature and heat of fusion) and chemical purity of coniferyl alcohol and D-mannose by differential scanning calorimetry (DSC). The measurements have been performed at different heating rates from 1-20 degrees C/min under atmospheric inert gas. From the DSC analysis, the onset temperature, peak temperature, and the heat of fusion of both the compounds were measured. They were found to increase with an increase in the heating rate. The chemical purity of coniferyl alcohol and D-mannose were determined based on the van't Hoff equation. The chemical purity of coniferyl alcohol was observed to be 99.54mol% with a correction factor of 1.44% at a 15 degrees C/min heating rate. The corresponding purity values for D-mannose were 98.98mol% at a correction factor of 6.76% and 20 degrees C/min. The obtained results showed that the chemical purity of both the compounds was found to decrease with an increase in the correction factor. Furthermore, this study also focuses on the solubility of both substances in ionic liquids by applying the continuum solvation model (COSMO-RS) using DSC measured melting properties as input.