Two tautomers in one crystal structure: ethyl 6(4)-oxo-1,6(1,4)-dihydro­pyrimidine-5-carboxyl­ate

The crystal structure of the title compound, C₇H₈N₂O₃, contains a 1:1 mixture of two tautomers, viz. ethyl 6-oxo-1,6-dihydro­pyrimidine-5-carboxyl­ate and ethyl 4-oxo-1,4-dihydro­pyrimidine-5-carboxyl­ate. The mol­ecules are linked into a three-dimensional network by N—H...O, C—H...O and C—H...N hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 292 K
• Mean [sigma](C-C) = 0.007 Å
• R factor = 0.053
• wR factor = 0.118
• Data-to-parameter ratio = 7.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT089_ALERT_3_C Poor Data / Parameter Ratio (Zmax .LT. 18) .....       6.97
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.69 Ratio
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.18 Ratio
PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          7
PLAT360_ALERT_2_C Short  C(sp3)-C(sp3) Bond  C6     -   C7     ...       1.41 Ang.

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           26.00
           From the CIF: _reflns_number_total               1526
           Count of symmetry unique reflns         1526
           Completeness (_total/calc)            100.00%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2001); software used to prepare material for publication: SHELXTL.

ethyl 6-oxo-1,6-dihydropyrimidine-5-carboxylate–ethyl 4-oxo-1,4-dihydropyrimidine-5-carboxylate (1/1)

Crystal data

C7H8N2O3	F(000) = 704
Mr = 168.15	Dx = 1.441 Mg m^−3
Monoclinic, Cc	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: C -2yc	Cell parameters from 1061 reflections
a = 4.768 (3) Å	θ = 2.3–20.2°
b = 25.590 (16) Å	µ = 0.12 mm^−1
c = 12.821 (8) Å	T = 292 K
β = 97.687 (10)°	Plate, colorless
V = 1550.4 (17) Å^3	0.40 × 0.10 × 0.03 mm
Z = 8

Data collection

Bruker SMART APEX CCD diffractometer	1121 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.053
Graphite monochromator	θmax = 26.0°, θmin = 1.6°
φ and ω scans	h = −5→5
4986 measured reflections	k = −29→31
1526 independent reflections	l = −15→15

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.053	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.118	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0587P)^2] where P = (Fo^2 + 2Fc^2)/3
1526 reflections	(Δ/σ)max < 0.001
219 parameters	Δρmax = 0.25 e Å^−3
4 restraints	Δρmin = −0.17 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
C1	0.5020 (10)	0.10368 (18)	0.5261 (4)	0.0447 (11)
C2	0.6793 (9)	0.14479 (16)	0.4943 (3)	0.0404 (11)
C3	0.8987 (12)	0.1440 (2)	0.6751 (4)	0.0548 (14)
H3	1.0341	0.1590	0.7252	0.066*
C4	0.5475 (12)	0.0869 (2)	0.6282 (4)	0.0589 (14)
H4	0.4319	0.0601	0.6468	0.071*
C5	0.2728 (11)	0.0773 (2)	0.4559 (5)	0.0589 (14)
C6	0.0149 (16)	0.0703 (3)	0.2828 (6)	0.090 (2)
H6A	−0.1379	0.0596	0.3210	0.108*
H6B	−0.0596	0.0956	0.2298	0.108*
C7	0.1191 (17)	0.0266 (3)	0.2338 (6)	0.108 (3)
H7A	0.2581	0.0377	0.1908	0.162*
H7B	−0.0339	0.0095	0.1906	0.162*
H7C	0.2042	0.0027	0.2865	0.162*
C8	0.6203 (10)	0.29602 (18)	0.6021 (3)	0.0382 (10)
C9	0.4030 (9)	0.25740 (18)	0.6016 (3)	0.0383 (11)
C10	0.5240 (11)	0.2486 (2)	0.7818 (4)	0.0479 (12)
H10	0.4921	0.2336	0.8452	0.057*
C11	0.7818 (10)	0.30764 (18)	0.6961 (3)	0.0429 (11)
H11	0.9249	0.3325	0.6985	0.051*
C12	0.6773 (10)	0.32283 (17)	0.5031 (3)	0.0434 (11)
C13	0.9330 (14)	0.3913 (2)	0.4335 (4)	0.0693 (17)
H13A	0.7644	0.4047	0.3913	0.083*
H13B	1.0290	0.3682	0.3899	0.083*
C14	1.1210 (16)	0.4348 (2)	0.4721 (5)	0.084 (2)
H14A	1.0220	0.4583	0.5128	0.126*
H14B	1.1788	0.4532	0.4133	0.126*
H14C	1.2849	0.4213	0.5153	0.126*
N1	0.8717 (8)	0.16304 (14)	0.5768 (3)	0.0426 (9)
H1	0.9673	0.1895	0.5602	0.051*
N2	0.7456 (11)	0.10560 (18)	0.7047 (3)	0.0646 (12)
N3	0.3623 (9)	0.23451 (16)	0.6977 (3)	0.0497 (11)
N4	0.7330 (8)	0.28318 (16)	0.7841 (3)	0.0474 (10)
H4A	0.8566	0.2903	0.8377	0.057*
O1	0.6751 (6)	0.16546 (13)	0.4074 (2)	0.0520 (9)
O2	0.1230 (10)	0.04496 (17)	0.4861 (4)	0.0884 (14)
O3	0.2429 (9)	0.09459 (17)	0.3562 (3)	0.0785 (13)
O4	0.2451 (7)	0.24239 (13)	0.5226 (2)	0.0558 (10)
O5	0.5775 (9)	0.31038 (14)	0.4162 (2)	0.0647 (10)
O6	0.8548 (8)	0.36256 (14)	0.5243 (2)	0.0561 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.038 (3)	0.051 (3)	0.046 (3)	0.000 (2)	0.008 (2)	−0.001 (2)
C2	0.040 (3)	0.044 (3)	0.035 (2)	0.006 (2)	0.000 (2)	−0.002 (2)
C3	0.058 (3)	0.069 (4)	0.037 (3)	0.005 (3)	0.002 (2)	0.000 (2)
C4	0.062 (4)	0.053 (3)	0.064 (4)	−0.006 (3)	0.017 (3)	0.011 (3)
C5	0.043 (3)	0.061 (3)	0.075 (4)	−0.004 (3)	0.013 (3)	−0.013 (3)
C6	0.089 (5)	0.080 (5)	0.092 (5)	−0.024 (4)	−0.017 (4)	−0.018 (4)
C7	0.121 (7)	0.084 (5)	0.108 (5)	0.010 (5)	−0.022 (5)	−0.028 (4)
C8	0.041 (3)	0.046 (3)	0.027 (2)	0.001 (2)	0.0014 (18)	−0.0050 (18)
C9	0.038 (3)	0.048 (3)	0.026 (2)	0.006 (2)	−0.0062 (19)	0.0002 (19)
C10	0.051 (3)	0.063 (3)	0.030 (2)	0.002 (3)	0.004 (2)	−0.001 (2)
C11	0.041 (3)	0.053 (3)	0.033 (2)	−0.001 (2)	−0.0009 (19)	−0.007 (2)
C12	0.045 (3)	0.048 (3)	0.036 (3)	0.006 (2)	0.001 (2)	0.000 (2)
C13	0.090 (5)	0.066 (4)	0.054 (3)	−0.006 (3)	0.016 (3)	0.012 (3)
C14	0.105 (6)	0.074 (4)	0.074 (4)	−0.026 (4)	0.015 (4)	0.000 (3)
N1	0.047 (3)	0.048 (2)	0.0309 (19)	−0.0016 (19)	−0.0011 (16)	0.0016 (17)
N2	0.071 (3)	0.074 (3)	0.048 (2)	−0.014 (3)	0.007 (2)	0.012 (2)
N3	0.052 (3)	0.067 (3)	0.0296 (19)	−0.006 (2)	0.0030 (18)	0.0010 (17)
N4	0.043 (2)	0.071 (3)	0.0261 (18)	−0.001 (2)	−0.0051 (16)	−0.0038 (18)
O1	0.046 (2)	0.068 (2)	0.0394 (18)	0.0001 (17)	−0.0026 (16)	0.0100 (16)
O2	0.078 (3)	0.092 (3)	0.095 (3)	−0.041 (3)	0.012 (2)	−0.006 (3)
O3	0.069 (3)	0.096 (3)	0.065 (3)	−0.025 (2)	−0.011 (2)	−0.008 (2)
O4	0.062 (2)	0.073 (2)	0.0284 (16)	−0.0162 (18)	−0.0102 (15)	−0.0012 (15)
O5	0.082 (3)	0.084 (2)	0.0270 (17)	−0.023 (2)	0.0030 (16)	0.0005 (17)
O6	0.070 (2)	0.059 (2)	0.0385 (16)	−0.0171 (19)	0.0055 (17)	−0.0006 (16)

Geometric parameters (Å, º)

C1—C4	1.366 (7)	C8—C9	1.431 (6)
C1—C2	1.442 (6)	C8—C12	1.500 (6)
C1—C5	1.483 (7)	C9—O4	1.239 (5)
C2—O1	1.230 (5)	C9—N3	1.402 (6)
C2—N1	1.385 (5)	C10—N3	1.290 (6)
C3—N2	1.310 (7)	C10—N4	1.329 (6)
C3—N1	1.341 (6)	C10—H10	0.9300
C3—H3	0.9300	C11—N4	1.338 (6)
C4—N2	1.355 (7)	C11—H11	0.9300
C4—H4	0.9300	C12—O5	1.195 (5)
C5—O2	1.190 (6)	C12—O6	1.328 (6)
C5—O3	1.343 (7)	C13—O6	1.467 (6)
C6—C7	1.406 (9)	C13—C14	1.473 (8)
C6—O3	1.476 (7)	C13—H13A	0.9700
C6—H6A	0.9700	C13—H13B	0.9700
C6—H6B	0.9700	C14—H14A	0.9600
C7—H7A	0.9600	C14—H14B	0.9600
C7—H7B	0.9600	C14—H14C	0.9600
C7—H7C	0.9600	N1—H1	0.8595
C8—C11	1.373 (6)	N4—H4A	0.8626
C4—C1—C2	118.5 (4)	N3—C9—C8	118.0 (4)
C4—C1—C5	116.6 (5)	N3—C10—N4	124.6 (4)
C2—C1—C5	124.9 (4)	N3—C10—H10	117.7
O1—C2—N1	118.3 (4)	N4—C10—H10	117.7
O1—C2—C1	129.1 (4)	N4—C11—C8	119.9 (5)
N1—C2—C1	112.5 (4)	N4—C11—H11	120.0
N2—C3—N1	123.8 (5)	C8—C11—H11	120.0
N2—C3—H3	118.1	O5—C12—O6	124.0 (4)
N1—C3—H3	118.1	O5—C12—C8	125.0 (4)
N2—C4—C1	126.0 (5)	O6—C12—C8	111.0 (4)
N2—C4—H4	117.0	O6—C13—C14	108.7 (5)
C1—C4—H4	117.0	O6—C13—H13A	110.0
O2—C5—O3	123.2 (5)	C14—C13—H13A	110.0
O2—C5—C1	123.0 (5)	O6—C13—H13B	110.0
O3—C5—C1	113.8 (5)	C14—C13—H13B	110.0
C7—C6—O3	110.2 (6)	H13A—C13—H13B	108.3
C7—C6—H6A	109.6	C13—C14—H14A	109.5
O3—C6—H6A	109.6	C13—C14—H14B	109.5
C7—C6—H6B	109.6	H14A—C14—H14B	109.5
O3—C6—H6B	109.6	C13—C14—H14C	109.5
H6A—C6—H6B	108.1	H14A—C14—H14C	109.5
C6—C7—H7A	109.5	H14B—C14—H14C	109.5
C6—C7—H7B	109.5	C3—N1—C2	124.5 (4)
H7A—C7—H7B	109.5	C3—N1—H1	122.1
C6—C7—H7C	109.5	C2—N1—H1	113.3
H7A—C7—H7C	109.5	C3—N2—C4	114.7 (4)
H7B—C7—H7C	109.5	C10—N3—C9	118.7 (4)
C11—C8—C9	118.3 (4)	C10—N4—C11	120.4 (4)
C11—C8—C12	120.0 (4)	C10—N4—H4A	126.1
C9—C8—C12	121.6 (4)	C11—N4—H4A	113.3
O4—C9—N3	116.7 (4)	C5—O3—C6	116.3 (5)
O4—C9—C8	125.3 (4)	C12—O6—C13	116.3 (4)
C4—C1—C2—O1	179.9 (5)	C11—C8—C12—O6	−11.1 (6)
C5—C1—C2—O1	0.7 (7)	C9—C8—C12—O6	170.1 (4)
C4—C1—C2—N1	−2.1 (6)	N2—C3—N1—C2	0.2 (7)
C5—C1—C2—N1	178.7 (4)	O1—C2—N1—C3	−179.9 (5)
C2—C1—C4—N2	0.6 (8)	C1—C2—N1—C3	1.9 (6)
C5—C1—C4—N2	179.8 (5)	N1—C3—N2—C4	−1.9 (8)
C4—C1—C5—O2	4.0 (7)	C1—C4—N2—C3	1.5 (8)
C2—C1—C5—O2	−176.8 (5)	N4—C10—N3—C9	−1.2 (8)
C4—C1—C5—O3	−178.5 (5)	O4—C9—N3—C10	179.3 (4)
C2—C1—C5—O3	0.7 (7)	C8—C9—N3—C10	−0.9 (6)
C11—C8—C9—O4	−178.7 (5)	N3—C10—N4—C11	2.6 (8)
C12—C8—C9—O4	0.2 (7)	C8—C11—N4—C10	−1.8 (7)
C11—C8—C9—N3	1.6 (6)	O2—C5—O3—C6	−1.6 (8)
C12—C8—C9—N3	−179.5 (4)	C1—C5—O3—C6	−179.1 (5)
C9—C8—C11—N4	−0.3 (7)	C7—C6—O3—C5	−90.7 (8)
C12—C8—C11—N4	−179.1 (4)	O5—C12—O6—C13	−1.4 (7)
C11—C8—C12—O5	168.8 (5)	C8—C12—O6—C13	178.6 (4)
C9—C8—C12—O5	−10.0 (7)	C14—C13—O6—C12	177.9 (5)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O4^i	0.86	2.00	2.847 (5)	170
C3—H3···N3^i	0.93	2.54	3.188 (7)	127
N4—H4A···O1^ii	0.86	2.01	2.789 (5)	151
C3—H3···O5^ii	0.93	2.55	3.307 (6)	139
C10—H10···O4^ii	0.93	2.50	3.135 (6)	125
C10—H10···O5^iii	0.93	2.55	3.281 (7)	136

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