5-Fluoro­uracil–di­methyl sulfoxide (1/1)

Hulme, A.T.; Tocher, D.A.

doi:10.1107/S1600536804022275

organic compounds

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ISSN: 2056-9890

Volume 60| Part 10| October 2004| Pages o1786-o1787

https://doi.org/10.1107/S1600536804022275

5-Fluorouracil–dimethyl sulfoxide (1/1)

Ashley T. Hulme ^a ^* and Derek A. Tocher ^a

^aChristopher Ingold Laboratory, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ, England
^*Correspondence e-mail: a.hulme@ucl.ac.uk

(Received 1 September 2004; accepted 8 September 2004; online 18 September 2004)

The title compound, C₄H₃FN₂O₂·C₂H₆OS, crystallizes in the monoclinic space group P2₁/c, with one molecule of 5-fluorouracil and one molecule of dimethyl sulfoxide (DMSO) in the asymmetric unit. The crystal structure contains hydrogen-bonded ribbons of alternating 5-fluorouracil and DMSO molecules which stack, forming non-interacting layers parallel to the (100) planes.

Comment

In the course of a polymorph screen performed on 5-fluorouracil three solvates were discovered; the crystal structure of one of these solvates is reported here. The title compound, (I), crystallizes in the space group P2₁/c with one molecule of 5-fluorouracil and one molecule of dimethyl sulfoxide (DMSO) in the asymmetric unit.

The S atom in the DMSO molecule is disordered over two sites, with a 95:5 occupancy ratio. The minor site (S20′) exhibits the opposite pyrimidisation of the DMSO molecule, compared to the major site (S20). Fig. 1 shows the asymmetric unit, with only the major sulfur position shown.

Two conventional hydrogen bonds, of the type N—H⋯O, occur in the structure. The O atom of the DMSO molecule acts as a hydrogen-bond acceptor for two symmetry-related 5-fluorouracil molecules (Table 1).

The crystal structure contains hydrogen-bonded ribbons of alternating 5-fluorouracil and DMSO molecules (Fig. 2). These ribbons stack, forming form non-interacting layers parallel to the (100) planes.

Figure 1
View (Watkin et al., 1996

) of the asymmetric unit of the title compound, with 50% probability displacement ellipsoids. H atoms are drawn as spheres of arbitrary radii.

Figure 2
Hydrogen-bonded ribbon motif, made up of alternating 5-fluorouracil and DMSO molecules. Hydrogen bonds are shown as dashed lines.

Experimental

5-Fluorouracil was obtained from the Aldrich Chemical Company Inc. The crystals of the title compound were grown by vapour diffusion of diethyl ether into a saturated solution of 5-fluorouracil in DMSO.

Crystal data

C₄H₃FN₂O₂·C₂H₆OS
M_r = 208.21
Monoclinic, P2₁/c
a = 9.8831 (10) Å
b = 10.8128 (11) Å
c = 8.6842 (9) Å
β = 107.397 (2)°
V = 885.58 (16) Å³
Z = 4
D_x = 1.562 Mg m⁻³
Mo Kα radiation
Cell parameters from 3031 reflections
θ = 2.9–28.0°
μ = 0.36 mm⁻¹
T = 150 (2) K
Block, colourless
0.29 × 0.21 × 0.11 mm

Data collection

Bruker SMART APEX diffractometer
Narrow-frame ω scans
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ) T_min = 0.903, T_max = 0.962
7672 measured reflections
2128 independent reflections
1922 reflections with I > 2σ(I)
R_int = 0.022
θ_max = 28.3°
h = −13 → 12
k = −14 → 14
l = −11 → 11

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.036
wR(F²) = 0.090
S = 1.07
2127 reflections
140 parameters
H atoms treated by a mixture of independent and constrained refinement
w = 1/[σ²(F_o²) + (0.0401P)² + 0.5099P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.40 e Å⁻³
Δρ_min = −0.54 e Å⁻³

Table 1
Hydrogen-bonding geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O20	0.79 (2)	2.04 (2)	2.838 (2)	175 (2)
N3—H3⋯O20ⁱ	0.82 (2)	1.97 (2)	2.790 (2)	173 (2)
N1—H1⋯S20′	0.79 (2)	2.56 (2)	3.266 (8)	149 (2)
N3—H3⋯S20ⁱ	0.82 (2)	2.89 (2)	3.666 (1)	157 (2)
Symmetry code: (i) $[1-x,{\script{1\over 2}}+y,{\script{1\over 2}}-z]$ .

The S atom in the DMSO molecule is disordered over two sites and was modelled anisotropically, with site occupancy 95:5. The S—O and S—C distances in the major and minor components were restrained to be equal within $[\pm]$ 0.01 Å. All H atoms on 5-fluorouracil were located in a difference map and were refined isotropically; N—H = 0.79 (2) and 0.82 (2) Å, and C—H = 0.94 (2) Å. The H-atom positions on the methyl group were idealized and refined using a riding model [C—H = 0.96 Å and U_iso(H) = 1.5U_eq(C)].

Data collection: SMART (Bruker, 1998 ); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin et al., 1996 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, str0220. DOI: https://doi.org/10.1107/S1600536804022275/ci6442sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536804022275/ci6442Isup2.hkl

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: SHELXL97.

5-Fluorouracil Dimethylsulfoxide (1/1) top

Crystal data top

C₂H₆OS·C₄H₃FN₂O₂	F(000) = 432
M_r = 208.21	D_x = 1.562 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3031 reflections
a = 9.8831 (10) Å	θ = 2.9–28.0°
b = 10.8128 (11) Å	µ = 0.36 mm⁻¹
c = 8.6842 (9) Å	T = 150 K
β = 107.397 (2)°	Block, colourless
V = 885.58 (16) Å³	0.29 × 0.21 × 0.11 mm
Z = 4

Data collection top

Bruker SMART APEX diffractometer	2128 independent reflections
Radiation source: sealed tube	1922 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.022
ω rotation with narrow frames scans	θ_max = 28.3°, θ_min = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −13→12
T_min = 0.903, T_max = 0.962	k = −14→14
7672 measured reflections	l = −11→11

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: found from delta F
R[F² > 2σ(F²)] = 0.036	Hydrogen site location: found from delta F
wR(F²) = 0.090	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ²(F_o²) + (0.0401P)² + 0.5099P] where P = (F_o² + 2F_c²)/3
2127 reflections	(Δ/σ)_max < 0.001
140 parameters	Δρ_max = 0.40 e Å⁻³
7 restraints	Δρ_min = −0.54 e Å⁻³

Special details top

Experimental. The sulfur atom in the DMSO molecule is disordered and is modelled anisotropically, with site occupancy 95:5.

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	Occ. (<1)
S20	0.15779 (4)	0.27388 (4)	−0.05029 (5)	0.01947 (14)	0.9452 (19)
S20'	0.1956 (8)	0.3387 (7)	0.0775 (10)	0.047 (3)	0.0548 (19)
O20	0.27984 (12)	0.22286 (10)	0.08812 (14)	0.0242 (3)
C20	0.02017 (18)	0.30934 (19)	0.0348 (2)	0.0310 (4)
H20A	−0.0187	0.2340	0.0621	0.047*	0.9452 (19)
H20B	−0.0530	0.3549	−0.0420	0.047*	0.9452 (19)
H20C	0.0576	0.3583	0.1303	0.047*	0.9452 (19)
H20D	0.0033	0.2592	0.1184	0.047*	0.0548 (19)
H20E	−0.0138	0.2671	−0.0667	0.047*	0.0548 (19)
H20F	−0.0289	0.3867	0.0289	0.047*	0.0548 (19)
C21	0.20530 (19)	0.42683 (17)	−0.0857 (2)	0.0296 (4)
H21A	0.2812	0.4246	−0.1335	0.044*	0.9452 (19)
H21B	0.2356	0.4710	0.0147	0.044*	0.9452 (19)
H21C	0.1249	0.4678	−0.1576	0.044*	0.9452 (19)
H21D	0.3041	0.4445	−0.0672	0.044*	0.0548 (19)
H21E	0.1541	0.5029	−0.0904	0.044*	0.0548 (19)
H21F	0.1691	0.3833	−0.1860	0.044*	0.0548 (19)
C6	0.57652 (17)	0.24074 (15)	0.4738 (2)	0.0203 (3)
F9	0.76106 (11)	0.21144 (9)	0.71240 (12)	0.0274 (2)
O7	0.48751 (13)	0.49901 (12)	0.21670 (14)	0.0288 (3)
O8	0.84328 (13)	0.45295 (12)	0.68615 (15)	0.0300 (3)
N1	0.50578 (15)	0.31511 (13)	0.34764 (17)	0.0202 (3)
N3	0.66006 (14)	0.47552 (13)	0.45536 (16)	0.0195 (3)
C2	0.54651 (16)	0.43374 (15)	0.33165 (18)	0.0194 (3)
C4	0.73994 (16)	0.40891 (15)	0.58632 (19)	0.0197 (3)
C5	0.68843 (17)	0.28387 (14)	0.58802 (19)	0.0199 (3)
H1	0.439 (2)	0.2926 (18)	0.276 (2)	0.019 (5)*
H3	0.685 (2)	0.548 (2)	0.448 (2)	0.027 (5)*
H6	0.5414 (19)	0.1598 (18)	0.474 (2)	0.020 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S20	0.0212 (2)	0.0176 (2)	0.0164 (2)	0.00214 (15)	0.00069 (16)	−0.00209 (14)
S20'	0.066 (7)	0.043 (6)	0.032 (5)	0.012 (5)	0.014 (5)	−0.003 (4)
O20	0.0213 (6)	0.0183 (6)	0.0276 (6)	0.0039 (4)	−0.0006 (5)	−0.0006 (4)
C20	0.0207 (8)	0.0428 (11)	0.0277 (9)	0.0050 (7)	0.0044 (7)	0.0087 (8)
C21	0.0272 (9)	0.0267 (9)	0.0331 (10)	0.0027 (7)	0.0064 (7)	0.0094 (7)
C6	0.0245 (8)	0.0151 (7)	0.0226 (8)	−0.0018 (6)	0.0091 (7)	−0.0008 (6)
F9	0.0293 (5)	0.0233 (5)	0.0253 (5)	0.0022 (4)	0.0017 (4)	0.0084 (4)
O7	0.0295 (6)	0.0268 (6)	0.0237 (6)	−0.0024 (5)	−0.0019 (5)	0.0068 (5)
O8	0.0273 (6)	0.0261 (6)	0.0280 (7)	−0.0053 (5)	−0.0048 (5)	0.0013 (5)
N1	0.0190 (7)	0.0211 (7)	0.0173 (7)	−0.0046 (5)	0.0007 (5)	−0.0029 (5)
N3	0.0211 (7)	0.0140 (6)	0.0212 (7)	−0.0032 (5)	0.0029 (5)	−0.0001 (5)
C2	0.0195 (7)	0.0206 (7)	0.0176 (7)	−0.0001 (6)	0.0050 (6)	−0.0008 (6)
C4	0.0194 (7)	0.0199 (7)	0.0190 (7)	−0.0005 (6)	0.0043 (6)	−0.0004 (6)
C5	0.0223 (7)	0.0180 (7)	0.0188 (7)	0.0020 (6)	0.0050 (6)	0.0033 (6)

Geometric parameters (Å, º) top

S20—O20	1.5288 (12)	C21—H21D	0.96
S20—C21	1.7710 (18)	C21—H21E	0.96
S20—C20	1.7729 (18)	C21—H21F	0.96
S20'—O20	1.492 (7)	C6—C5	1.330 (2)
S20'—C20	1.691 (7)	C6—N1	1.371 (2)
S20'—C21	1.734 (7)	C6—H6	0.94 (2)
C20—H20A	0.96	F9—C5	1.3534 (18)
C20—H20B	0.96	O7—C2	1.2192 (19)
C20—H20C	0.96	O8—C4	1.2215 (19)
C20—H20D	0.96	N1—C2	1.364 (2)
C20—H20E	0.96	N1—H1	0.79 (2)
C20—H20F	0.96	N3—C2	1.377 (2)
C21—H21A	0.96	N3—C4	1.378 (2)
C21—H21B	0.96	N3—H3	0.82 (2)
C21—H21C	0.96	C4—C5	1.446 (2)

O20—S20—C21	106.60 (8)	C2—N1—C6	122.53 (14)
O20—S20—C20	105.89 (8)	C2—N1—H1	114.2 (14)
C21—S20—C20	98.44 (9)	C6—N1—H1	123.3 (14)
O20—S20—H20E	126.7	C2—N3—C4	127.20 (14)
C21—S20—H20E	110.1	C2—N3—H3	116.1 (14)
O20—S20—H21F	126.7	C4—N3—H3	116.6 (14)
C20—S20—H21F	110.9	O7—C2—N1	122.98 (15)
H20E—S20—H21F	104.4	O7—C2—N3	121.84 (15)
O20—S20'—C20	111.9 (5)	N1—C2—N3	115.18 (14)
O20—S20'—C21	110.2 (4)	O8—C4—N3	122.22 (15)
C20—S20'—C21	103.2 (4)	O8—C4—C5	125.40 (15)
S20'—C20—H20C	66.5	N3—C4—C5	112.37 (13)
C5—C6—N1	120.15 (15)	C6—C5—F9	121.11 (14)
C5—C6—H6	123.3 (12)	C6—C5—C4	122.48 (14)
N1—C6—H6	116.6 (12)	F9—C5—C4	116.41 (14)

C5—C6—N1—C2	0.9 (2)	N1—C6—C5—F9	−179.01 (14)
C6—N1—C2—O7	177.16 (15)	N1—C6—C5—C4	0.5 (2)
C6—N1—C2—N3	−2.8 (2)	O8—C4—C5—C6	−178.74 (17)
C4—N3—C2—O7	−176.16 (16)	N3—C4—C5—C6	0.2 (2)
C4—N3—C2—N1	3.8 (2)	O8—C4—C5—F9	0.8 (2)
C2—N3—C4—O8	176.46 (16)	N3—C4—C5—F9	179.76 (13)
C2—N3—C4—C5	−2.5 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O20	0.79 (2)	2.04 (2)	2.838 (2)	175 (2)
N3—H3···O20ⁱ	0.82 (2)	1.97 (2)	2.790 (2)	173 (2)
N1—H1···S20′	0.79 (2)	2.56 (2)	3.266 (8)	149 (2)
N3—H3···S20ⁱ	0.82 (2)	2.89 (2)	3.666 (1)	157 (2)

Symmetry code: (i) −x+1, y+1/2, −z+1/2.

Acknowledgements

The authors acknowledge the Research Councils UK Basic Technology Programme for supporting `Control and Prediction of the Organic Solid State'.

References

Bruker (1998). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany. Google Scholar
Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany. Google Scholar
Watkin, D. J., Prout, C. K. & Pearce, L. J. (1996). CAMERON. Chemical Crystallography Laboratory, Oxford, England. Google Scholar

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