ISSN:
1573-904X
Keywords:
oxonicotinic acids
;
polymorphism
;
phase transition
;
polymorphic quantitation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Two polymorphs of l,2-dihydro-6-neopentyl-2-oxonicotinic acid have been characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), differential scanning calorimetry (DSC), and thermal (hot-stage) microscopy (HSM). In batch-scale preparation, form I was crystallized in ethanol–water (3:1), while form II was obtained by recrystallization from acetone–water (2:1). The melting points for forms I and II are 193 and 196°C, respectively. Thermal studies (DSC and HSM) showed that form II melts at 196°C, while form I melts at 193°C, immediately followed by a resolidification and remelt at 196°C. The conversion of form II to form I was accomplished by recrystallization from ethanol or methanol, and the form I-to-form II transition was obtained by controlled heating of form I around 194°C. Quantitative XRD was used to determine the polymorphic composition, with a detection limit of less than 1% of the minor form and a linearity of 0–10% form I in form II (correlation coefficient of 0.999).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1016498731952
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