5,5-Di­hydroxy­barbituric acid monohydrate (alloxan dihydrate)

Lewis, T.C.; Tocher, D.A.

doi:10.1107/S1600536804021555

organic compounds

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Volume 60| Part 10| October 2004| Pages o1689-o1690

https://doi.org/10.1107/S1600536804021555

5,5-Dihydroxybarbituric acid monohydrate (alloxan dihydrate)

Thomas C. Lewis ^a and Derek A. Tocher ^a ^*

^aDepartment of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, England
^*Correspondence e-mail: d.a.tocher@ucl.ac.uk

(Received 25 August 2004; accepted 1 September 2004; online 11 September 2004)

The title compound, C₄H₄N₂O₅·H₂O, was crystallized from both tetrahydrofuran and 1,4-dioxane solutions of alloxan as part of an experimental polymorph screen on alloxan.

Comment

It has previously been reported that alloxan has two hydrates, viz. 5,5-dihydroxybarbituric acid (Singh, 1965 ; Harrowfield et al., 1989 ) and 5,5-dihydroxybarbituric acid trihydrate (Mootz & Jeffrey, 1965 ). The crystal structure of a new hydrate of alloxan, namely 5,5-dihydroxybarbituric acid monohydrate, (I), has one organic molecule and one water molecule in the asymmetric unit (Fig. 1). The heterocyclic ring has an envelope conformation with the flap at C5, with the angle between the mean C4/N3/C2/N1/C6 and C4/C5/C6 planes being 20.1 (2)°. The C—N bond lengths are in the range 1.360 (2)–1.378 (2) Å, with the bond lengths associated with the sp³-hybridized carbon being 1.536 (2) and 1.527 (2) Å for C4—C5 and C5—C6, respectively.

The crystal packing (Fig. 2) consists of a series of ribbon motifs arranged in an overall sheet structure. Water molecules lie in the sheets and between the ribbons. Each water molecule acts as a hydrogen-bond donor to a carbonyl group in the same sheet and to a hydroxyl group on a molecule in the adjacent sheet. Each water molecule also acts as a hydrogen-bond acceptor for a hydroxyl group on a molecule in the same sheet. The axial hydroxyl group on each molecule acts as a hydrogen-bond donor to the unique carbonyl of a molecule in an adjacent sheet. The D⋯A distances within the sheets are in the range 2.6380 (19)–2.9516 (19) Å, whilst the distances between the sheets are 2.6958 (17) and 2.9973 (19) Å. All potential hydrogen-bond acceptors and donors participate in the hydrogen bonding.

Figure 1
The asymmetric unit of (I

), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The crystal packing of (I

), showing the N—H⋯O and O—H⋯O hydrogen-bonding interactions as dashed lines; the view is approximately on to the (01 $[\overline 1]$ ) plane.

Experimental

5,5-Dihydroxybarbituric acid monohydrate was crystallized over a number of weeks by slow evaporation of tetrahydrofuran and 1,4-dioxane solutions of alloxan (0.002–0.03 mol dm⁻³) at room temperature, forming colourless plate crystals.

Crystal data

C₄H₄N₂O₅·H₂O
M_r = 178.11
Triclinic, $[P\overline 1]$
a = 6.6730 (11) Å
b = 7.5834 (13) Å
c = 7.6157 (13) Å
α = 105.401 (3)°
β = 93.134 (3)°
γ = 115.089 (2)°
V = 330.26 (10) Å³
Z = 2
D_x = 1.791 Mg m⁻³
Mo Kα radiation
Cell parameters from 712 reflections
θ = 2.8–25.0°
μ = 0.17 mm⁻¹
T = 150 (2) K
Plate, colourless
0.23 × 0.11 × 0.07 mm

Data collection

Bruker SMART APEX diffractometer
Narrow-frame ω scans
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ) T_min = 0.962, T_max = 0.988
2972 measured reflections
1536 independent reflections
1274 reflections with I > 2σ(I)
R_int = 0.021
θ_max = 28.3°
h = −8 → 8
k = −9 → 9
l = −10 → 10

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.043
wR(F²) = 0.102
S = 1.07
1536 reflections
133 parameters
All H-atom parameters refined
w = 1/[σ²(F_o²) + (0.0502P)² + 0.0119P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.24 e Å⁻³

Table 1
Hydrogen-bonding geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O6ⁱ	0.89 (2)	1.95 (2)	2.8366 (18)	170.7 (19)
N3—H3⋯O4ⁱⁱ	0.81 (2)	2.11 (2)	2.8736 (18)	157 (2)
O7—H7⋯O2ⁱⁱⁱ	0.87 (2)	1.83 (3)	2.6958 (17)	173 (2)
O8—H8⋯O1Wⁱⁱⁱ	0.80 (2)	1.87 (2)	2.6380 (19)	161 (2)
O1W—H1W⋯O6^iv	0.92 (3)	2.04 (3)	2.9516 (19)	173 (2)
O1W—H2W⋯O7ⁱⁱ	0.82 (3)	2.28 (3)	2.9973 (19)	147 (3)
Symmetry codes: (i) 1-x,-y,2-z; (ii) 1-x,1-y,1-z; (iii) 1+x,y,z; (iv) 1-x,-y,1-z.

H atoms were refined freely with an isotropic model.

Data collection: SMART (Bruker, 2000 ); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997 ); molecular graphics: SHELXTL (Bruker, 2000; Bruno et al., 2002 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536804021555/bt6506sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536804021555/bt6506Isup2.hkl

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: SAINT; data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000); software used to prepare material for publication: SHELXL97.

5,5-dihydroxybarbituric acid monohydrate top

Crystal data top

C₄H₄N₂O₅·H₂O	Z = 2
M_r = 178.11	F(000) = 184
Triclinic, P1	D_x = 1.791 Mg m⁻³
a = 6.6730 (11) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.5834 (13) Å	Cell parameters from 712 reflections
c = 7.6157 (13) Å	θ = 2.8–25.0°
α = 105.401 (3)°	µ = 0.17 mm⁻¹
β = 93.134 (3)°	T = 150 K
γ = 115.089 (2)°	Plate, colourless
V = 330.26 (10) Å³	0.23 × 0.11 × 0.07 mm

Data collection top

Bruker SMART APEX diffractometer	1536 independent reflections
Radiation source: fine-focus sealed tube	1274 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.021
ω rotation scans with narrow frames	θ_max = 28.3°, θ_min = 2.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −8→8
T_min = 0.962, T_max = 0.988	k = −9→9
2972 measured reflections	l = −10→10

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.102	All H-atom parameters refined
S = 1.07	w = 1/[σ²(F_o²) + (0.0502P)² + 0.0119P] where P = (F_o² + 2F_c²)/3
1536 reflections	(Δ/σ)_max < 0.001
133 parameters	Δρ_max = 0.34 e Å⁻³
0 restraints	Δρ_min = −0.24 e Å⁻³

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
O2	0.2526 (2)	0.32902 (18)	0.90727 (17)	0.0200 (3)
O4	0.6356 (2)	0.34785 (19)	0.43384 (16)	0.0214 (3)
O6	0.7119 (2)	0.02976 (19)	0.86645 (17)	0.0207 (3)
O7	0.9445 (2)	0.42247 (18)	0.76705 (17)	0.0194 (3)
O8	0.7906 (2)	0.09757 (19)	0.54162 (17)	0.0204 (3)
O1W	0.0411 (3)	0.1981 (2)	0.2940 (2)	0.0339 (4)
N1	0.4853 (2)	0.1829 (2)	0.8839 (2)	0.0160 (3)
N3	0.4626 (2)	0.3615 (2)	0.6818 (2)	0.0171 (3)
C2	0.3919 (3)	0.2946 (2)	0.8279 (2)	0.0156 (4)
C4	0.6073 (3)	0.3162 (2)	0.5801 (2)	0.0160 (4)
C5	0.7514 (3)	0.2387 (2)	0.6700 (2)	0.0155 (4)
C6	0.6456 (3)	0.1366 (2)	0.8121 (2)	0.0154 (3)
H1	0.421 (4)	0.128 (3)	0.969 (3)	0.033 (6)*
H3	0.398 (4)	0.416 (3)	0.641 (3)	0.035 (6)*
H7	1.035 (4)	0.383 (4)	0.813 (3)	0.046 (7)*
H8	0.859 (4)	0.149 (3)	0.472 (3)	0.034 (6)*
H1W	0.107 (5)	0.117 (4)	0.244 (4)	0.059 (8)*
H2W	0.030 (5)	0.268 (4)	0.232 (4)	0.072 (10)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O2	0.0185 (6)	0.0251 (7)	0.0231 (7)	0.0143 (5)	0.0074 (5)	0.0101 (5)
O4	0.0264 (7)	0.0273 (7)	0.0190 (7)	0.0157 (6)	0.0081 (5)	0.0136 (5)
O6	0.0236 (7)	0.0270 (7)	0.0256 (7)	0.0179 (6)	0.0120 (5)	0.0175 (5)
O7	0.0158 (6)	0.0205 (7)	0.0262 (7)	0.0093 (5)	0.0038 (5)	0.0121 (5)
O8	0.0292 (7)	0.0213 (7)	0.0204 (7)	0.0161 (6)	0.0143 (5)	0.0116 (5)
O1W	0.0465 (9)	0.0343 (8)	0.0412 (9)	0.0277 (8)	0.0276 (8)	0.0235 (7)
N1	0.0171 (7)	0.0204 (7)	0.0173 (7)	0.0110 (6)	0.0068 (6)	0.0116 (6)
N3	0.0198 (7)	0.0201 (7)	0.0191 (7)	0.0133 (6)	0.0049 (6)	0.0106 (6)
C2	0.0155 (8)	0.0151 (8)	0.0173 (8)	0.0079 (7)	0.0019 (6)	0.0056 (7)
C4	0.0171 (8)	0.0128 (8)	0.0192 (8)	0.0068 (7)	0.0033 (6)	0.0068 (6)
C5	0.0162 (8)	0.0170 (8)	0.0172 (8)	0.0090 (7)	0.0054 (6)	0.0084 (7)
C6	0.0144 (8)	0.0155 (8)	0.0186 (9)	0.0075 (7)	0.0038 (6)	0.0077 (7)

Geometric parameters (Å, º) top

O2—C2	1.2171 (19)	N1—C6	1.360 (2)
O4—C4	1.209 (2)	N1—C2	1.378 (2)
O6—C6	1.2188 (19)	N1—H1	0.89 (2)
O7—C5	1.405 (2)	N3—C4	1.368 (2)
O7—H7	0.87 (2)	N3—C2	1.368 (2)
O8—C5	1.3706 (19)	N3—H3	0.81 (2)
O8—H8	0.80 (2)	C4—C5	1.536 (2)
O1W—H1W	0.92 (3)	C5—C6	1.527 (2)
O1W—H2W	0.82 (3)

C5—O7—H7	104.6 (16)	O4—C4—N3	123.23 (15)
C5—O8—H8	109.7 (16)	O4—C4—C5	120.38 (15)
H1W—O1W—H2W	115 (3)	N3—C4—C5	116.18 (14)
C6—N1—C2	126.62 (15)	O8—C5—O7	115.10 (14)
C6—N1—H1	119.2 (13)	O8—C5—C6	106.53 (13)
C2—N1—H1	113.9 (13)	O7—C5—C6	107.51 (13)
C4—N3—C2	125.45 (14)	O8—C5—C4	112.19 (14)
C4—N3—H3	116.6 (15)	O7—C5—C4	102.10 (12)
C2—N3—H3	117.1 (16)	C6—C5—C4	113.50 (13)
O2—C2—N3	123.04 (15)	O6—C6—N1	121.83 (15)
O2—C2—N1	119.95 (15)	O6—C6—C5	121.52 (14)
N3—C2—N1	117.00 (15)	N1—C6—C5	116.49 (14)

C4—N3—C2—O2	−175.55 (16)	O4—C4—C5—C6	−159.76 (15)
C4—N3—C2—N1	4.2 (2)	N3—C4—C5—C6	25.3 (2)
C6—N1—C2—O2	−178.33 (16)	C2—N1—C6—O6	−177.16 (16)
C6—N1—C2—N3	1.9 (2)	C2—N1—C6—C5	7.3 (2)
C2—N3—C4—O4	166.85 (16)	O8—C5—C6—O6	40.3 (2)
C2—N3—C4—C5	−18.4 (2)	O7—C5—C6—O6	−83.59 (19)
O4—C4—C5—O8	−38.9 (2)	C4—C5—C6—O6	164.28 (15)
N3—C4—C5—O8	146.15 (14)	O8—C5—C6—N1	−144.19 (14)
O4—C4—C5—O7	84.86 (18)	O7—C5—C6—N1	91.92 (17)
N3—C4—C5—O7	−90.07 (16)	C4—C5—C6—N1	−20.2 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O6ⁱ	0.89 (2)	1.95 (2)	2.8366 (18)	170.7 (19)
N3—H3···O4ⁱⁱ	0.81 (2)	2.11 (2)	2.8736 (18)	157 (2)
O7—H7···O2ⁱⁱⁱ	0.87 (2)	1.83 (3)	2.6958 (17)	173 (2)
O8—H8···O1Wⁱⁱⁱ	0.80 (2)	1.87 (2)	2.6380 (19)	161 (2)
O1W—H1W···O6^iv	0.92 (3)	2.04 (3)	2.9516 (19)	173 (2)
O1W—H2W···O7ⁱⁱ	0.82 (3)	2.28 (3)	2.9973 (19)	147 (3)

Symmetry codes: (i) −x+1, −y, −z+2; (ii) −x+1, −y+1, −z+1; (iii) x+1, y, z; (iv) −x+1, −y, −z+1.

Acknowledgements

This research was supported by the EPSRC in funding a studentship for TCL. The authors acknowledge the Research Councils UK Basic Technology Programme for supporting `Control and Prediction of the Organic Solid State'. For more information on this work, please visit https://www.chem.ucl.ac.uk/basictechorg/.

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