Decanedioic Acid (C10H18O4)/Dodecanedioic Acid (C12H22O4) System: Polymorphism of the Components and Experimental Phase Diagram

✍ Scribed by Lourdes Ventolà; Laura Bayés; Raül Benages; Francisco Javier Novegil-Anleo; Miquel Ángel Cuevas-Diarte; Teresa Calvet; Denise Mondieig

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: German
• Weight: 312 KB
• Volume: 91
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200890140

✦ Synopsis

The experimental temperature/composition phase diagram of the binary system decanedioic acid (C 10 H 18 O 4 )/dodecanedioic acid (C 12 H 22 O 4 ) was established by combining X-ray powder diffraction (XRD), differential-scanning calorimetry (DSC), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermo-optical microscopy (TOM). Both compounds crystallize in the same ordered form, C (P2 1 /c), which is the phase that melts in both cases. The C form melts in C 12 H 22 O 4 earlier than in C 10 H 18 O 4 , in contrast to other unbranched-chain compounds (alkanes, alkanols, and alkanoic acids) in which the melting temperatures increase as the C-atom number rises. Contrary to what might be expected, total solid-state miscibility is not observed. The C 10 H 18 O 4 /C 12 H 22 O 4 binary system shows a complex phase diagram. At low temperatures, a new monoclinic form, C i (P2 1 /c), stabilizes as a result of the disorder of composition in the mixed samples; two [C þ C i ] domains appear. Upon heating, four solid -solid and seven solid -liquid domains appear related by eutectic and peritectic invariants. All the crystallographic forms observed are isostructural.