Conformations of barbiturates related to pentobarbitone. I. Crystal structure oftrans-5-ethyl-5-but-1?-enyl barbituric acid

1981 ◽  
Vol 11 (5-6) ◽  
pp. 125-133 ◽  
Author(s):  
G. P. Jones ◽  
P. R. Andrews
Keyword(s):  
Crystal Structure ◽  
Barbituric Acid

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

2005 ◽  
Vol 61 (4) ◽  
pp. 464-472 ◽  
Author(s):  
Gary S. Nichol ◽  
William Clegg
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Barbituric Acid ◽  
Crystal Packing ◽  
Variable Temperature ◽  
Mirror Plane ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Acta Cryst ◽  
Space Group

The crystal structure of barbituric acid dihydrate (C4H4N2O3·2H2O) has twice been reported as orthorhombic, space group Pnma, with all atoms (except for CH2 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 P21/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 β angle in the monoclinic structure is temperature dependent; at 100 K β is around 94° and it decreases in magnitude towards 90° 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 sp 3-hybridized C atom of barbituric acid.

scholarly journals The crystal structure of barbituric acid dihydrate

1961 ◽  
Vol 14 (8) ◽  
pp. 881-887 ◽  
Author(s):  
G. A. Jeffrey ◽  
S. Ghose ◽  
J. O. Warwicker
Keyword(s):  
Crystal Structure ◽  
Barbituric Acid

Crystal structure of barbituric acid (1,4)-dioxane solvate at -173°C

2004 ◽  
Vol 34 (1) ◽  
pp. 61-65 ◽  
Author(s):  
Sadad Al-Saqqar ◽  
Larry R. Falvello ◽  
Tatiana Soler
Keyword(s):  
Crystal Structure ◽  
Barbituric Acid
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