Dimethyl formamide solvates of CaCl 2

Abstract

The water of hydration in inorganic salts plays a vital role in stabilising their crystal structures, as is evidenced by the fact that on dehydration the structures change radically. In order to understand further the role played by the solvent in the development of an ordered lattice, dimethyl formamide (DMF) solvates of inorganic salts have been prepared and studied. DMF is a good solvent and has a fairly high dielectric constant. Two compounds, viz. CaCl 2 · 2.5 DMF and CaCl 2 ·- 2 DMF, were prepared and were found to be moisture-sensitive. Their thermal stability was determined by micro-thermogravimetry. Both compounds started to lose DMF at 338 K and passed through an intermediate phase, CaCl 2 · DMF, which was stable in the temperature range 408–463 K. However, the differential thermogravimetric run showed four peaks which were also confirmed by differential scanning calorimetry. The X-ray powder diffraction pattern of both the solvates is also presented along with the chemical analysis. A comparative study of their thermal stability is presented.