On the polymorphism of barbituric acid derivatives

Caillet, J.; Claverie, P.

doi:10.1107/s0567740880009594

Cited by 19 publications

(8 citation statements)

References 9 publications

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“…Many derivatives of barbituric acid also crystallize in various polymorphic forms. For example, barbital (5,5diethylbarbituric acid) was reported to form four polymorphs with crystal structures determined for three of them (Craven et al, 1969;Caillet & Claverie, 1980), whereas for violuric acid, a 5-substituted derivative of barbituric acid [pyrimidine-2,4,5,6-(1H,3H)-tetrone monohydrate], two polymorphic modifications were found: an orthorhombic one (Craven & Mascarenhas, 1964;Craven & Takei, 1964;Nichol & Clegg, 2005b) and a monoclinic one (Guille et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Polymorphism of urea–barbituric acid co-crystals

Gryl

Krawczuk

Stadnicka

2008

Acta Crystallogr Sect B

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The crystal structures of three polymorphs found for the addition complex of urea and barbituric acid are described and compared. Two polymorphs are monoclinic, space groups P2(1)/c and Cc, whereas the third is triclinic, P1. The displacement of electron density towards the mesomeric forms, corresponding to the tautomeric forms of higher stability, of the barbituric acid molecule seem to influence the type of hydrogen bonds formed, which in turn determines the different packing topology in the polymorphs. While the polymorphic forms can be easily differentiated at the first-level graph-set analysis of their hydrogen-bonding patterns, a higher-level analysis enables important features of the mutual spatial arrangement of the structural components to be revealed.

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Section: Introductionmentioning

confidence: 99%

Polymorphism of urea–barbituric acid co-crystals

Gryl

Krawczuk

Stadnicka

2008

Acta Crystallogr Sect B

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“…Polymorphism within the barbiturate family is widespread and well studied also in view of pharmaceutical interest. [35][36][37][38] The three crystal forms are easily prepared separately and could thus be used independently in the reaction with gases. A similar experiment has been carried out before by Stowell, Griesser, Byrn et al 39 in the course of the investigation of the reactivity of indomethacine amorphous and crystal forms with ammonia.…”

Section: Introductionmentioning

confidence: 99%

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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“…Barbituric acid is the parent molecule of the barbiturate family of drugs, which are of crystallographic interest not least for their propensity to form polymorphs. The 5,5-dialkyl derivatives are those which are pharmacologically active and which have been most extensively characterized by X-ray crystallography (Caillet & Claverie, 1980;Cleverley & Williams, 1959;Craven et al, , 1982, 1971McMullan et al, 1978;Nichol & Clegg, 2005a,b;Platteau et al, 2005;Sambyal et al, 1995;Williams, 1973Williams, , 1974. Contemporary research continues to focus on barbituric acid polymorphism as a model system for developing computational polymorph prediction techniques, something that is of major importance to the pharmaceutical industry (Lewis et al, 2004(Lewis et al, , 2005.…”

Section: Introductionmentioning

confidence: 99%

A variable-temperature study of a phase transition in barbituric acid dihydrate

Nichol

Clegg

2005

Acta Crystallogr Sect B

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The crystal structure of barbituric acid dihydrate (C4H4N2O3*2H2O) has twice been reported as orthorhombic, space group Pnma, with all atoms (except for CH(2) H atoms) lying on the mirror plane [Al-Karaghouli et al. (1977). Acta Cryst. B33, 1655-1660; Jeffrey et al. (1961). Acta Cryst. 14, 881-887]. The present study has found that at low temperatures, below 200 K, the crystal structure is no longer orthorhombic but is non-merohedrally twinned monoclinic, space group P2(1)/n. This phase is stable down to 100 K. Above 220 K the crystal structure is orthorhombic, and between 200 and 220 K the structure undergoes a phase change, with the monoclinic-to-orthorhombic phase transition itself taking place at around 216-217 K. The size of the beta angle in the monoclinic structure is temperature dependent; at 100 K beta is around 94 degrees and it decreases in magnitude towards 90 degrees as the temperature increases. Although the hydrogen-bonding motifs are the same for both crystal systems, there are significant differences in the crystal packing, in particular the out-of-plane displacement of the two water molecules and the sp3-hybridized C atom of barbituric acid.

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On the polymorphism of barbituric acid derivatives

Cited by 19 publications

References 9 publications

Polymorphism of urea–barbituric acid co-crystals

Polymorphism of urea–barbituric acid co-crystals

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

A variable-temperature study of a phase transition in barbituric acid dihydrate

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