A kinetic study on the isothermal transition of polymorphic forms of tolbutamide and mefenamic acid in the solid state at high temperatures.

Polymorphic properties of micronized mefenamic acid, nabumetone, paracetamol and tolbutamide produced by rapid expansion of supercritical solutions (RESS)

“…As specified in Table 5 the DSC scan of the unprocessed material shows a transition peak at T trs = 432.9 K and a melting peak at T m = 503.6 K which is in good agreement with literature data ranging from 500 to 506 K [11,20,21,22,82,83]. On the other hand, data given in literature for the transformation of form I into form II (443-463 K) and of form I to III (448 to 451 K [11,20,21,22,82,83] are significant higher than the result of this investigation.…”

“…On the other hand, data given in literature for the transformation of form I into form II (443-463 K) and of form I to III (448 to 451 K [11,20,21,22,82,83] are significant higher than the result of this investigation.…”

“…The observed melting temperature at T m = 401 K and an enthalpy of fusion of h m = 91.5 J g −1 correspond to the data of form I H [33,40] published in literature. Depending on the particular reference and therewith often the heating rate, melting occurs at temperatures between T m = 398.6 K and 403.6 K with an enthalpy of fusion ranging from h m = 88.0 to 100.6 J g −1 [33,34,40,46,83,88,[91][92][93]. Thus, DSC analysis of the unprocessed material indicates the existence of mainly form I L .…”

Investigations on Solid–Solid Phase Transformation of 5-Methyl-2-[(4-Methyl-2-Nitrophenyl)Amino]-3- Thiophenecarbonitrile

“…Thorough characterization of the kinetics can enhance the fundamental understanding of the underlying processes, assist in the rational design and development of materials and processes, and address uncertainties regarding the stability of the particular phases. In the 1980's, Ohnishi et al [13][14][15] performed extensive kinetic studies on the isothermal transitions of some drug molecules at high temperatures; transformation rates were obtained by fitting the data (time vs. percent transformed) to several kinetic models from which the Arrhenius activation energies were calculated. Sheridan and Anwar 16 used time-resolved energy-dispersive X-ray diffraction to study the solid-state phase transformation of sulfanilamide from the b-form to the g-form.…”

Additive-Induced Metastable Single Crystal of Mefenamic Acid

“…Resonance interaction and an intra hydrogen bonding between the bridging imino and carboxyl groups stabilize the coplanar structure (11). In addition, a number of other materials properties of fenamates have been studied including solubility and dissolution rate, (12,13), manufacturability and tableting properties (14,15) and polymorphic transformation (16,17), respectively. This makes this an ideal system for analysis of the effect of structurally similar impurities on crystallization.…”