Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270112005495/eg3085sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270112005495/eg3085Isup2.hkl | |
Chemical Markup Language (CML) file https://doi.org/10.1107/S0108270112005495/eg3085Isup3.cml |
CCDC reference: 873889
The treatment of hydrogen atoms for molecule 1 (in the mirror plane): the NH hydrogen atom was refined freely. Methyl H atoms were identified in difference syntheses; the geometry was idealized (C—H 0.98 Å, H—C—H 109.5 °) and the methyl groups refined as rigid groups allowed to rotate but not tip. For all methyl H, U(H) was set to 1.5Ueq(C). For the carbons C2 and C4 one hydrogen lay to a good approximation in the mirror plane; this hydrogen was retained, together with one of the other methyl H atoms, with half and full occupation, respectively, and the group was refined using a riding model. For carbon C3 the H atoms were not in the mirror plane and a disordered model with three half-occupied H atoms was thus used.
The treatment of hydrogen atoms for molecule 2 (in the general position): the NH hydrogen was refined freely. The methyl H atoms were identified and incorporated into rigid groups as above. For carbons C2' and C4', the hydrogen positions were acceptable, but the methyl group at C3' showed indistinct maxima and refined slowly. For this reason a model of six half H atoms was used, corresponding to two equally spaced and half-occupied positions of the methyl H atoms. Even this model converged slowly, and the true disorder may be more serious. In both molecules there is a short intramolecular contact from the NH hydrogen to one of the disordered H atoms at C3 (1.96 Å for molecule 1 and 1.84 Å for molecule 2; the latter leads to an `Alert B' message from CHECKCIF).
In the absence of significant anomalous dispersion, Friedel opposite reflections were merged and the Flack parameter is thus meaningless.
Data collection: CrysAlis PRO (Oxford Diffraction, 2011); cell refinement: CrysAlis PRO (Oxford Diffraction, 2011); data reduction: CrysAlis PRO (Oxford Diffraction, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).
C4H10N2O | Dx = 1.221 Mg m−3 |
Mr = 102.14 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Cmc21 | Cell parameters from 11117 reflections |
a = 20.5281 (15) Å | θ = 2.7–30.7° |
b = 8.1474 (3) Å | µ = 0.09 mm−1 |
c = 9.9637 (4) Å | T = 100 K |
V = 1666.43 (15) Å3 | Block, colourless |
Z = 12 | 0.4 × 0.3 × 0.2 mm |
F(000) = 672 |
Oxford Diffraction Xcalibur Eos diffractometer | 1172 reflections with I > 2σ(I) |
Radiation source: Enhance (Mo) X-ray Source | Rint = 0.027 |
Graphite monochromator | θmax = 29.1°, θmin = 2.7° |
Detector resolution: 16.1419 pixels mm-1 | h = −27→28 |
ω scans | k = −11→11 |
36795 measured reflections | l = −13→13 |
1214 independent reflections |
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)] = 0.031 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.087 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.08 | w = 1/[σ2(Fo2) + (0.0501P)2 + 0.5442P] where P = (Fo2 + 2Fc2)/3 |
1214 reflections | (Δ/σ)max = 0.040 |
117 parameters | Δρmax = 0.28 e Å−3 |
1 restraint | Δρmin = −0.19 e Å−3 |
C4H10N2O | V = 1666.43 (15) Å3 |
Mr = 102.14 | Z = 12 |
Orthorhombic, Cmc21 | Mo Kα radiation |
a = 20.5281 (15) Å | µ = 0.09 mm−1 |
b = 8.1474 (3) Å | T = 100 K |
c = 9.9637 (4) Å | 0.4 × 0.3 × 0.2 mm |
Oxford Diffraction Xcalibur Eos diffractometer | 1172 reflections with I > 2σ(I) |
36795 measured reflections | Rint = 0.027 |
1214 independent reflections |
R[F2 > 2σ(F2)] = 0.031 | 1 restraint |
wR(F2) = 0.087 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.08 | Δρmax = 0.28 e Å−3 |
1214 reflections | Δρmin = −0.19 e Å−3 |
117 parameters |
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. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) 20.5281 (0.0015) x + 0.0000 (0.0000) y + 0.0000 (0.0001) z = 0.0000 (0.0000) * 0.0000 (0.0000) C1 * 0.0000 (0.0000) C2 * 0.0000 (0.0000) C3 * 0.0000 (0.0000) C4 * 0.0000 (0.0000) N1 * 0.0000 (0.0000) N3 * 0.0000 (0.0000) O1 Rms deviation of fitted atoms = 0.0000 20.4297 (0.0018) x + 0.6938 (0.0032) y - 0.4785 (0.0073) z = 7.1982 (0.0022) Angle to previous plane (with approximate e.s.d.) = 5.61 (0.01) * -0.0095 (0.0013) C1' * 0.0496 (0.0011) C2' * -0.0109 (0.0010) C3' * 0.0106 (0.0010) C4' * -0.0418 (0.0014) N1' * 0.0284 (0.0013) N3' * -0.0265 (0.0011) O1' Rms deviation of fitted atoms = 0.0294 |
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. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
C1 | 0.0000 | 0.4081 (2) | 0.8582 (2) | 0.0180 (4) | |
C2 | 0.0000 | 0.1132 (3) | 0.8124 (2) | 0.0241 (4) | |
H2A | 0.0000 | 0.1531 | 0.7218 | 0.036* | |
H2B | 0.0382 | 0.0476 | 0.8273 | 0.036* | |
C3 | 0.0000 | 0.2106 (3) | 1.0478 (3) | 0.0289 (5) | |
H3A | 0.0188 | 0.1013 | 1.0611 | 0.043* | 0.50 |
H3B | −0.0448 | 0.2119 | 1.0817 | 0.043* | 0.50 |
H3C | 0.0260 | 0.2920 | 1.0966 | 0.043* | 0.50 |
C4 | 0.0000 | 0.6993 (2) | 0.9065 (3) | 0.0246 (5) | |
H4A | 0.0000 | 0.7698 | 0.9837 | 0.037* | |
H4B | 0.0382 | 0.7202 | 0.8536 | 0.037* | |
N1 | 0.0000 | 0.2505 (2) | 0.9046 (2) | 0.0253 (4) | |
H01 | 0.0000 | 0.508 (5) | 1.030 (4) | 0.024 (7)* | |
N3 | 0.0000 | 0.5296 (2) | 0.95021 (19) | 0.0239 (4) | |
O1 | 0.0000 | 0.4384 (2) | 0.73592 (17) | 0.0259 (4) | |
C1' | 0.33529 (6) | 0.5919 (2) | 0.15028 (16) | 0.0199 (3) | |
C2' | 0.32948 (8) | 0.8835 (2) | 0.20144 (19) | 0.0272 (3) | |
H2'1 | 0.3288 | 0.8395 | 0.2929 | 0.041* | |
H2'2 | 0.2916 | 0.9548 | 0.1880 | 0.041* | |
H2'3 | 0.3695 | 0.9471 | 0.1879 | 0.041* | |
C3' | 0.32403 (9) | 0.7936 (3) | −0.03531 (18) | 0.0312 (4) | |
H3'1 | 0.3267 | 0.9132 | −0.0440 | 0.047* | 0.50 |
H3'2 | 0.2828 | 0.7549 | −0.0734 | 0.047* | 0.50 |
H3'3 | 0.3604 | 0.7429 | −0.0837 | 0.047* | 0.50 |
H3'4 | 0.3199 | 0.6942 | −0.0900 | 0.047* | 0.50 |
H3'5 | 0.3638 | 0.8524 | −0.0606 | 0.047* | 0.50 |
H3'6 | 0.2862 | 0.8644 | −0.0503 | 0.047* | 0.50 |
C4' | 0.34493 (8) | 0.30117 (18) | 0.09814 (18) | 0.0261 (3) | |
H4'1 | 0.3843 | 0.2878 | 0.1527 | 0.039* | |
H4'2 | 0.3478 | 0.2306 | 0.0187 | 0.039* | |
H4'3 | 0.3067 | 0.2702 | 0.1512 | 0.039* | |
N1' | 0.32734 (7) | 0.74860 (17) | 0.10550 (15) | 0.0249 (3) | |
H01' | 0.3371 (9) | 0.484 (4) | −0.031 (3) | 0.037 (6)* | |
N3' | 0.33904 (7) | 0.47151 (18) | 0.05633 (14) | 0.0239 (3) | |
O1' | 0.33841 (7) | 0.55955 (15) | 0.27212 (11) | 0.0262 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0254 (9) | 0.0143 (9) | 0.0145 (9) | 0.000 | 0.000 | 0.0011 (8) |
C2 | 0.0336 (10) | 0.0168 (9) | 0.0219 (11) | 0.000 | 0.000 | −0.0021 (9) |
C3 | 0.0509 (13) | 0.0180 (10) | 0.0177 (11) | 0.000 | 0.000 | 0.0042 (9) |
C4 | 0.0399 (11) | 0.0159 (9) | 0.0181 (10) | 0.000 | 0.000 | 0.0003 (9) |
N1 | 0.0488 (11) | 0.0143 (8) | 0.0128 (8) | 0.000 | 0.000 | 0.0014 (8) |
N3 | 0.0451 (10) | 0.0160 (9) | 0.0107 (9) | 0.000 | 0.000 | 0.0016 (8) |
O1 | 0.0454 (9) | 0.0208 (9) | 0.0116 (8) | 0.000 | 0.000 | 0.0003 (7) |
C1' | 0.0232 (6) | 0.0194 (7) | 0.0170 (7) | −0.0007 (5) | −0.0007 (5) | 0.0005 (6) |
C2' | 0.0405 (8) | 0.0157 (7) | 0.0254 (8) | 0.0010 (5) | −0.0027 (7) | −0.0024 (7) |
C3' | 0.0493 (9) | 0.0254 (9) | 0.0190 (8) | 0.0056 (6) | 0.0003 (7) | 0.0057 (7) |
C4' | 0.0396 (8) | 0.0169 (7) | 0.0219 (8) | 0.0004 (6) | −0.0003 (6) | −0.0015 (6) |
N1' | 0.0405 (7) | 0.0171 (6) | 0.0171 (6) | 0.0030 (4) | −0.0010 (5) | 0.0003 (6) |
N3' | 0.0390 (7) | 0.0176 (6) | 0.0152 (7) | −0.0014 (5) | 0.0006 (5) | 0.0000 (6) |
O1' | 0.0434 (7) | 0.0202 (5) | 0.0150 (6) | 0.0004 (5) | −0.0012 (5) | 0.0014 (5) |
C1—O1 | 1.243 (3) | C2'—N1' | 1.458 (2) |
C1—N3 | 1.349 (3) | C2'—H2'1 | 0.98 |
C1—N1 | 1.364 (3) | C2'—H2'2 | 0.98 |
C2—N1 | 1.447 (3) | C2'—H2'3 | 0.98 |
C2—H2A | 0.96 | C3'—N1' | 1.452 (2) |
C2—H2B | 0.96 | C3'—H3'1 | 0.98 |
C3—N1 | 1.464 (3) | C3'—H3'2 | 0.98 |
C3—H3A | 0.98 | C3'—H3'3 | 0.98 |
C3—H3B | 0.98 | C3'—H3'4 | 0.98 |
C3—H3C | 0.98 | C3'—H3'5 | 0.98 |
C4—N3 | 1.450 (3) | C3'—H3'6 | 0.98 |
C4—H4A | 0.96 | C4'—N3' | 1.4540 (19) |
C4—H4B | 0.96 | C4'—H4'1 | 0.98 |
N3—H01 | 0.81 (4) | C4'—H4'2 | 0.98 |
C1'—O1' | 1.2438 (19) | C4'—H4'3 | 0.98 |
C1'—N3' | 1.358 (2) | N3'—H01' | 0.88 (3) |
C1'—N1' | 1.362 (2) | ||
O1—C1—N3 | 121.3 (2) | N1'—C2'—H2'3 | 109.5 |
O1—C1—N1 | 121.3 (2) | H2'1—C2'—H2'3 | 109.5 |
N3—C1—N1 | 117.4 (2) | H2'2—C2'—H2'3 | 109.5 |
N1—C2—H2A | 109.6 | N1'—C3'—H3'1 | 109.5 |
N1—C2—H2B | 109.4 | N1'—C3'—H3'2 | 109.5 |
H2A—C2—H2B | 109.5 | H3'1—C3'—H3'2 | 109.5 |
N1—C3—H3A | 109.5 | N1'—C3'—H3'3 | 109.5 |
N1—C3—H3B | 109.5 | H3'1—C3'—H3'3 | 109.5 |
H3A—C3—H3B | 109.5 | H3'2—C3'—H3'3 | 109.5 |
N1—C3—H3C | 109.5 | N1'—C3'—H3'4 | 109.5 |
H3A—C3—H3C | 109.5 | N1'—C3'—H3'5 | 109.5 |
H3B—C3—H3C | 109.5 | H3'4—C3'—H3'5 | 109.5 |
N3—C4—H4A | 109.3 | N1'—C3'—H3'6 | 109.5 |
N3—C4—H4B | 109.6 | H3'4—C3'—H3'6 | 109.5 |
H4A—C4—H4B | 109.5 | H3'5—C3'—H3'6 | 109.5 |
C1—N1—C2 | 120.8 (2) | N3'—C4'—H4'1 | 109.5 |
C1—N1—C3 | 122.61 (19) | N3'—C4'—H4'2 | 109.5 |
C2—N1—C3 | 116.55 (19) | H4'1—C4'—H4'2 | 109.5 |
C1—N3—C4 | 119.72 (19) | N3'—C4'—H4'3 | 109.5 |
C1—N3—H01 | 120 (3) | H4'1—C4'—H4'3 | 109.5 |
C4—N3—H01 | 120 (3) | H4'2—C4'—H4'3 | 109.5 |
O1'—C1'—N3' | 121.13 (17) | C1'—N1'—C3' | 123.96 (15) |
O1'—C1'—N1' | 121.61 (15) | C1'—N1'—C2' | 119.25 (15) |
N3'—C1'—N1' | 117.25 (15) | C3'—N1'—C2' | 116.42 (15) |
N1'—C2'—H2'1 | 109.5 | C1'—N3'—C4' | 119.77 (15) |
N1'—C2'—H2'2 | 109.5 | C1'—N3'—H01' | 126 (2) |
H2'1—C2'—H2'2 | 109.5 | C4'—N3'—H01' | 114 (2) |
O1—C1—N1—C2 | 0.000 | O1'—C1'—N1'—C3' | 179.36 (17) |
N3—C1—N1—C2 | 180.0 | N3'—C1'—N1'—C3' | −1.3 (2) |
O1—C1—N1—C3 | 180.0 | O1'—C1'—N1'—C2' | 6.6 (2) |
N3—C1—N1—C3 | 0.000 | N3'—C1'—N1'—C2' | −174.01 (14) |
O1—C1—N3—C4 | 0.000 | O1'—C1'—N3'—C4' | 1.8 (2) |
N1—C1—N3—C4 | 180.0 | N1'—C1'—N3'—C4' | −177.57 (13) |
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H01···O1i | 0.81 (4) | 2.10 (4) | 2.859 (3) | 155 (4) |
N3′—H01′···O1′ii | 0.88 (3) | 2.00 (3) | 2.8431 (19) | 162 (3) |
Symmetry codes: (i) x, −y+1, z+1/2; (ii) x, −y+1, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | C4H10N2O |
Mr | 102.14 |
Crystal system, space group | Orthorhombic, Cmc21 |
Temperature (K) | 100 |
a, b, c (Å) | 20.5281 (15), 8.1474 (3), 9.9637 (4) |
V (Å3) | 1666.43 (15) |
Z | 12 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.4 × 0.3 × 0.2 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur Eos diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 36795, 1214, 1172 |
Rint | 0.027 |
(sin θ/λ)max (Å−1) | 0.685 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.031, 0.087, 1.08 |
No. of reflections | 1214 |
No. of parameters | 117 |
No. of restraints | 1 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.28, −0.19 |
Computer programs: CrysAlis PRO (Oxford Diffraction, 2011), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), XP (Siemens, 1994).
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H01···O1i | 0.81 (4) | 2.10 (4) | 2.859 (3) | 155 (4) |
N3'—H01'···O1'ii | 0.88 (3) | 2.00 (3) | 2.8431 (19) | 162 (3) |
Symmetry codes: (i) x, −y+1, z+1/2; (ii) x, −y+1, z−1/2. |
In the course of our studies of adducts of di(organosulfonyl)amines with various N-methyl-substituted ureas [methylurea (Henschel et al., 2002; Wölper et al., 2010), 1,1-dimethylurea (Henschel et al., 2002; Wölper et al., 2010), 1,3-dimethylurea (Wijaya et al., 1997; Hamann, Henschel et al., 2002), tetramethylurea (Hamann, Wijaya et al., 2002; Zerbe et al., 2008) and trimethylurea (Wölper et al., 2011; Döring et al., 2012)], we recently noted to our surprise that the structure of trimethylurea itself has never been published. The structures of the other N-methylureas have been determined as follows: methylurea, space group P212121, Huiszoon & Tiemessen (1976); 1,1-dimethylurea, P21/n, Pathirana et al. (1994), and as a footnote/supplementary material also by Fairlie et al. (1994); 1,3-dimethylurea, space group corrected from Cc to Fdd2 by Marsh (2004), Pérez-Folch et al. (1997); tetramethylurea, a liquid at room temperature, C2/c, Frampton & Parkes (1996). The latter two structures both display imposed twofold symmetry.
We report here the hitherto `missing' structure of trimethylurea, (I). The compound as purchased proved to contain single crystals and one of these was used to determine the structure. The suppliers Alfa Aesar were unfortunately unable to provide details of crystallization conditions; recrystallization experiments in our hands have so far failed to provide evidence of any other crystalline forms. The same crystal form was obtained from e.g. tetrahydrofuran/n-heptane by liquid diffusion.
The title compound crystallizes in the space group Cmc21 with Z = 12 (Z' = 1.5). The first independent molecule (unprimed atoms) lies in the mirror plane at x = 0, whereas the second molecule (primed atoms) occupies a general position in the plane at x ≈ 1/3 (Fig. 1). Molecule 2 has an r.m.s. deviation from planarity of only 0.03 Å; a least-squares fit of both molecules also gives an r.m.s. deviation of 0.03 Å. In both molecules, the NH hydrogen is trans to the C═O group, as is observed for all the methylated ureas for which this configuration is possible; one may speculate that this facilitates the formation of hydrogen-bonded chains of molecules.
Molecular dimensions, such as the C═O bond lengths of 1.244 (2) and 1.243 (3) Å and the N—C—N angles of 117.25 (15) and 117.4 (2)°, may be considered normal.
The packing involves classical N—H···O═C hydrogen-bond systems (Table 1), linking adjacent molecules via the c-glide operator and thus leading to chains of molecules with the simple and common graph-set C(4), parallel to the polar c axis (Fig. 2). The chains involve exclusively either molecule 1 or molecule 2, and, as defined by the general direction of the H···O vector, are, respectively, parallel or antiparallel to the c axis. The chain pattern as seen along the b axis (Fig. 3) is thus AABAAB at intervals of ca a/6; in other words, there are twice as many chains antiparallel to the c axis as parallel to the c axis, which is an unusual packing feature. The pattern of chains then extends itself by b-axis translation to form the layers perpendicular to the a axis as noted above for the individual molecules.
For 1,3-dimethylurea, which also forms hydrogen-bonded chains in a polar space group but has only one independent molecule, all chains are necessarily parallel to the polar c axis (Pérez-Folch et al., 1997). We have recently reinvestigated the 1,3-dimethylurea system and have established the presence of a new polymorph, upon which we shall report.