Thermogravimetric characteristics of barbituric acid and some of its derivatives

Berlin, Alexandre; Taylor, Murray E.; Robinson, Robert J.

doi:10.1016/0003-2670(61)80089-5

Cited by 7 publications

(1 citation statement)

References 5 publications

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“…As previously noted by Berlin et al in a TGA study, the dihydrate form loses the water at 60 uC. 44 We have been able to demonstrate by means of variable temperature XRPD experiments that, upon water release, this form undergoes a phase transformation with formation of Form II of barbituric acid (see Fig. 1).…”

Section: Dehydration Of the Dihydrate Formsupporting

confidence: 80%

Gas–solid reactions between the different polymorphic modifications of barbituric acid and amines

Braga¹,

Cadoni²,

Grepioni³

et al. 2006

CrystEngComm

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The two known crystalline polymorphic forms of barbituric acid (C 4 H 4 N 2 O 3 ) (form I and form II) and the dihydrate form [(C 4 H 4 N 2 O 3 )?2H 2 O] have been reacted with vapours of ammonia, methylamine, and dimethylamine and the crystalline products investigated by means of single crystal and powder X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and infrared spectroscopy. It has been shown that form I, II and the dihydrate form of barbituric acid react with ammonia leading to the same crystalline ammonium barbiturate salt NH 4 (C 4 H 3 N 2 O 3 ) 1a, while the gas-solid reactions of form II with methylamine, and dimethylamine yield the corresponding crystalline salts, CH 3 NH 3 (C 4 H 3 N 2 O 3 ) 1b and (CH 3 ) 2 NH 2 (C 4 H 3 N 2 O 3 ) 1c. Thermal desorption of the bases at ca. 200 uC leads to formation of a new crystal form of barbituric acid, form III, as confirmed by H 1 -NMR spectroscopy and by chemical behaviour. De-hydration of the dihydrate form has also been investigated showing that it releases water to yield exclusively crystals of form II.

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Section: Dehydration Of the Dihydrate Formsupporting

confidence: 80%