Buy article online - an online subscription or single-article purchase is required to access this article.
Download citation
Download citation
link to html
The title compound, C3H6N2O, crystallizes with imposed twofold symmetry in the space group I41/a. The five-membered ring displays a half-chair conformation. N—H...O hydrogen bonds connect the mol­ecules to form R22(8) rings and thence ribbons parallel to the a and b axes. These inter­sect via O2H2 rings involving longer H...O contacts. The crystal was merohedrally twinned. Preliminary indications of the higher symmetry space group I41/amd, which would require the ring to be planar, proved to be incorrect. A previous brief report of the structure in Fdd2 is also probably incorrect.

Supporting information


Crystallographic Information File (CIF)
Contains datablocks I, global


Structure factor file (CIF format)
Contains datablock I


Chemical Markup Language (CML) file
Supplementary material

CCDC reference: 971130

Introduction top

We are inter­ested in the structures of derivatives and solvent adducts of urea (see e.g. Jones et al., 2013; Taouss et al., 2013, and references therein). Initial attempts to obtain adducts of imidazolidin-2-one (ethyl­eneurea) with various solvents yielded only crystals of the uncomplexed starting material. However, to our surprise, the structure of this simple substance, the title compound, (I), has never been reported in detail. Some adducts such as the hemihydrate (Kapon & Reisner, 1989) and the 1:1 urea adduct [Deutsch & Bernstein, 2008; Cambridge Structural Database (CSD; Allen, 2002) refcode HOJLIC] are known, but the structure of imidazolidin-2-one is only mentioned as part of the Supplementary Material to a study of deep eutectic solvents (Zhang et al., 2009), where it is presented solely as a displacement ellipsoid plot. The authors provided the CSD with information concerning the space group (Fdd2) and cell constants (a = 11.140, b = 10.530 and c = 13.270 Å, with standard uncertainties > 0.1 Å), but requests for the atomic coordinates do not seem to have been complied with. The R value is also high (0.14).

Experimental top

Synthesis and crystallization top

The title compound, obtained from Acros and used without further purification, was dissolved in a 1:1 mixture of 1,4-dioxane and methanol (by volume) and overlayered with di­ethyl ether. Colourless blocks formed overnight.

Refinement top

Crystal data, data collection and structure refinement details are summarized in Table 1. N-bound H atoms were refined freely. The treatment of methyl­ene H atoms used a riding model starting from calculated positions, with C—H = 0.99 Å and Uiso(H) = 1.2Ueq(C).

The structure was refined as a merohedral twin; the occupation of the minor component refined to 0.208 (2).

A rigid-body libration correction (Schomaker & Trueblood, 1968) gave an Rlib value of 0.062 and corrected bond lengths (Å) as follows: O1—C1 = 1.240, C1—N2 = 1.371, N2—C3 = 1.461 and C3—C3i = 1.547 Å.

Comment top

In our hands, (I) displayed an I-centred tetra­gonal cell. Initial analysis of the data suggested the space group I41/amd, but this was rejected for three reasons: (i) the Rint value was too high at 0.167; (ii) some reflections corresponding to d-glide absences were present (mean I/σ 2.8, cf. 0.6 for the a-glide absences); and (iii) although the structure could be solved, all atoms lay exactly in the mirror plane at x = 0, which is unexpected for the unsaturated imidazolidine ring system. A refinement of this structure led to poor R values and high U components parallel to the molecular plane. All further calculations were therefore performed in the lower symmetry space group I41/a. We note in passing that the matrix [1 1 0, 1 1 0, 0 0 1] generates a metrically F-centred orthorhombic cell with a = b = 10.779 and c = 13.163 Å, cf. the cell of Zhang et al. (2009). The structure was refined as a merohedral twin; as is well known, such twinning lowers the Rint value in the higher Laue group [see (i) above)].

The molecule of I) is shown in Fig. 1. It displays crystallographic twofold symmetry, with atoms C1 and O1 lying along the twofold axis. Because of the symmetry, standard ring numbering is not used. The molecular dimensions (Table 2) can be regarded as normal, e.g. the N—Csp2 bond length is 1.3652 (11) Å, cf. average 1.366 Å for some 16000 values extracted from the CSD (Version?). However, it should be noted that the librational corrections are significant (e.g. 0.008 Å for the C—C bond). The ring displays a slightly distorted half-chair conformation.

The main feature of the molecular packing of I) is a classical N—H···O hydrogen bond (Table 3), which connects the molecules to form ribbons parallel to the a and the b axes. Rings of the well known graph set R22(8) (Etter, 1990) are clearly recognisable (Fig. 2) and are a well known feature in the packing of many urea derivatives, e.g. the closely related structure of the analogous six-membered ring system 3,4,5,6-tetra­hydro­pyrimidin-2(1H)-one (Rizal et al., 2008). The mutual orientation of the ribbons is such that those parallel to a pass through the inter­stices between those parallel to b, and vice versa. However, there are further N—H···O contacts, although they are quite long and have angles of only 118 (1)°, between the two sets of ribbons. At the junctions of the two sets, four-membered O2H2 rings can be recognized (Fig. 3), with transannular O···O distances of 2.775 (2) Å (symmetry operator from atom O1 to its transannular equivalent: -1/4 + y, 5/4 - x, 5/4 - z).

Related literature top

For related literature, see: Allen (2002); Deutsch & Bernstein (2008); Etter (1990); Jones et al. (2013); Kapon & Reisner (1989); Rizal et al. (2008); Schomaker & Trueblood (1968); Taouss et al. (2013); Zhang et al. (2009).

Computing details top

Data collection: CrysAlis PRO (Agilent, 2013); cell refinement: CrysAlis PRO (Agilent, 2013); data reduction: CrysAlis PRO (Agilent, 2013); 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).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I). Displacement ellipsoids are drawn at the 50% probability level and only the asymmetric unit is numbered.
[Figure 2] Fig. 2. A packing diagram for (I), viewed parallel to the a axis, showing three hydrogen-bonded ribbons. Hydrogen bonds are indicated by dashed lines. H atoms not involved in hydrogen bonds have been omitted.
[Figure 3] Fig. 3. The junction point of two ribbons parallel to b (right) and a (left), showing in each case two eight-membered rings. Contacts between perpendicular ribbons are indicated as thin dashed lines and thick dashed lines indicate hydrogen bonds.
Imidazolidin-2-one top
Crystal data top
C3H6N2ODx = 1.496 Mg m3
Mr = 86.10Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I41/aCell parameters from 2735 reflections
a = 7.6219 (3) Åθ = 3.1–29.2°
c = 13.1632 (9) ŵ = 0.12 mm1
V = 764.69 (7) Å3T = 100 K
Z = 8Block, colourless
F(000) = 3680.20 × 0.20 × 0.18 mm
Data collection top
Oxford Xcalibur Eos
546 reflections with I > 2σ(I)
Radiation source: Enhance (Mo) X-ray SourceRint = 0.043
Graphite monochromatorθmax = 30.9°, θmin = 3.1°
Detector resolution: 16.1419 pixels mm-1h = 1011
ω scansk = 1010
10301 measured reflectionsl = 1818
583 independent reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.032Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.079H atoms treated by a mixture of independent and constrained refinement
S = 1.07 w = 1/[σ2(Fo2) + (0.0439P)2 + 0.2482P]
where P = (Fo2 + 2Fc2)/3
583 reflections(Δ/σ)max < 0.001
34 parametersΔρmax = 0.24 e Å3
0 restraintsΔρmin = 0.21 e Å3
Crystal data top
C3H6N2OZ = 8
Mr = 86.10Mo Kα radiation
Tetragonal, I41/aµ = 0.12 mm1
a = 7.6219 (3) ÅT = 100 K
c = 13.1632 (9) Å0.20 × 0.20 × 0.18 mm
V = 764.69 (7) Å3
Data collection top
Oxford Xcalibur Eos
546 reflections with I > 2σ(I)
10301 measured reflectionsRint = 0.043
583 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0320 restraints
wR(F2) = 0.079H atoms treated by a mixture of independent and constrained refinement
S = 1.07Δρmax = 0.24 e Å3
583 reflectionsΔρmin = 0.21 e Å3
34 parameters
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
O10.50000.75000.51960 (7)0.0143 (2)
C10.50000.75000.42554 (9)0.0114 (3)
N20.52887 (11)0.60730 (11)0.36512 (5)0.0136 (2)
H020.5135 (18)0.504 (2)0.3903 (10)0.024 (3)*
C30.49143 (14)0.64940 (12)0.25925 (6)0.0148 (2)
Atomic displacement parameters (Å2) top
O10.0157 (4)0.0181 (5)0.0090 (4)0.0003 (4)0.0000.000
C10.0092 (5)0.0135 (6)0.0115 (5)0.0004 (5)0.0000.000
N20.0199 (5)0.0113 (4)0.0096 (3)0.0009 (3)0.0010 (3)0.0001 (3)
C30.0193 (4)0.0155 (4)0.0096 (4)0.0001 (4)0.0009 (3)0.0007 (3)
Geometric parameters (Å, º) top
O1—C11.2382 (15)C3—C3i1.5391 (18)
C1—N21.3652 (11)N2—H020.859 (16)
C1—N2i1.3652 (11)C3—H3A0.9900
N2—C31.4583 (11)C3—H3B0.9900
O1—C1—N2125.63 (5)C3—N2—H02122.8 (9)
O1—C1—N2i125.63 (5)N2—C3—H3A111.4
N2—C1—N2i108.75 (11)C3i—C3—H3A111.4
C1—N2—C3110.48 (8)N2—C3—H3B111.4
N2—C3—C3i101.69 (5)C3i—C3—H3B111.4
C1—N2—H02118.7 (9)H3A—C3—H3B109.3
O1—C1—N2—C3170.90 (5)C1—N2—C3—C3i21.92 (12)
N2i—C1—N2—C39.10 (5)N2—C3—C3i—N2i25.20 (13)
Symmetry code: (i) x+1, y+3/2, z.
Hydrogen-bond geometry (Å, º) top
N2—H02···O1ii0.859 (16)2.275 (15)3.1253 (10)170.0 (12)
N2—H02···O1iii0.859 (16)2.509 (15)3.0076 (9)117.8 (10)
Symmetry codes: (ii) x+1, y+1, z+1; (iii) y+5/4, x1/4, z1/4.
Selected geometric parameters (Å, º) top
O1—C11.2382 (15)N2—C31.4583 (11)
C1—N21.3652 (11)C3—C3i1.5391 (18)
N2i—C1—N2—C39.10 (5)N2—C3—C3i—N2i25.20 (13)
C1—N2—C3—C3i21.92 (12)
Symmetry code: (i) x+1, y+3/2, z.

Experimental details

Crystal data
Chemical formulaC3H6N2O
Crystal system, space groupTetragonal, I41/a
Temperature (K)100
a, c (Å)7.6219 (3), 13.1632 (9)
V3)764.69 (7)
Radiation typeMo Kα
µ (mm1)0.12
Crystal size (mm)0.20 × 0.20 × 0.18
Data collection
DiffractometerOxford Xcalibur Eos
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
10301, 583, 546
(sin θ/λ)max1)0.723
R[F2 > 2σ(F2)], wR(F2), S 0.032, 0.079, 1.07
No. of reflections583
No. of parameters34
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.24, 0.21

Computer programs: CrysAlis PRO (Agilent, 2013), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), XP (Siemens, 1994).

Hydrogen-bond geometry (Å, º) top
N2—H02···O1ii0.859 (16)2.275 (15)3.1253 (10)170.0 (12)
N2—H02···O1iii0.859 (16)2.509 (15)3.0076 (9)117.8 (10)
Symmetry codes: (ii) x+1, y+1, z+1; (iii) y+5/4, x1/4, z1/4.

Subscribe to Acta Crystallographica Section C: Structural Chemistry

The full text of this article is available to subscribers to the journal.

If you have already registered and are using a computer listed in your registration details, please email for assistance.

Buy online

You may purchase this article in PDF and/or HTML formats. For purchasers in the European Community who do not have a VAT number, VAT will be added at the local rate. Payments to the IUCr are handled by WorldPay, who will accept payment by credit card in several currencies. To purchase the article, please complete the form below (fields marked * are required), and then click on `Continue'.
E-mail address* 
Repeat e-mail address* 
(for error checking) 

Format*   PDF (US $40)
   HTML (US $40)
   PDF+HTML (US $50)
In order for VAT to be shown for your country javascript needs to be enabled.

VAT number 
(non-UK EC countries only) 

Terms and conditions of use
Contact us

Follow Acta Cryst. C
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds