Anhydrous 1-methyl­imidazolidin-2-one

The title compound, C₄H₈N₂O, crystallizes from the vapor phase in sheets supported by a one-dimensional hydrogen-bonded network. The mol­ecular unit shows planar ureido -NCH₃ groups, but the slight out-of-plane hydrogen-bond geometry may be indicative of some pyramidalization of the ureido -NH groups.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.070
• wR factor = 0.161
• Data-to-parameter ratio = 13.7

checkCIF/PLATON results

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Alert level C
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         C1

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

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

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S1. Comment

The imidazolidin-2-one functional group is of primary importance in the transfer of carbon dioxide by biotin-dependent enzymes (Carey et al., 2004; Attwood & Wallace, 2002). It is therefore important that the structural characteristics of this unit be well understood. In the course of our work on biomimetic carbon dioxide fixation, we crystallized anhydrous N-methylimidazolidin-2-one, (I), and report here its crystal structure.

The molecular unit in (I) shows the five-membered heterocycle. The ring is only slightly enveloped, with an average internal torsion angle of 4.6° and a mean deviation from planarity of 0.0273 Å. The metrical parameters in the heterocycle are essentially identical to those in unsubstituted imidazolidin-2-one (Kapon & Reisner, 1989), and to those in biotin itself (DeTitta et al., 1976). Methylated atom N2 is planar, indicative of largely sp²-hybrid character. This is consistent with N-silyl-substituted imidazolidin-2-ones (Szalay et al., 2005), as well as with N1'-methoxycarbonylbiotin methyl ester (Stallings et al., 1980), which also exhibit essentially planar ureido N atoms. However, the planar N atoms are at variance with some theoretical work which seems to indicate that the N atoms in urea and related molecules have considerable sp³ character·(Meier & Coussens, 1992). Some insight may be gained from the solid state packing in (I), which is supported by a one-dimensional network of hydrogen bonds (O···N = 2.87 Å). Neighboring hydrogen-bonded chains are packed to form a two-dimensional sheet (Fig. 2). The individual hydrogen-bonding interactions are 19.8° out of the heterocycle plane, and may be indicative of some pyramidalization of the —NH group.

S2. Experimental

The title compopund was purchased from Aldrich. The microcrystalline powder was placed in a flame-sealed ampoule and the apparatus stored in a 363 K oven for one week. This procedure gave colorless blocks suitable for X-ray diffraction.

S3. Refinement

H atoms were added in idealized positions as riding atoms with C—H distances of 0.96 Å for methyl and 0.96 Å for the rest; The N—H distance is 0.86 Å. The isotropic displacement parameters were set at 1.5U_eq of the parent atom for the methyl H atoms and 1.2U_eq for the rest.

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); 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 1997); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. Displacement ellipsoid drawing of (I) (35% probability ellipsoids).
	Fig. 2. Solid-state packing diagram of (I), viewed down the crystallographic a axis.

N-methylimidazolidin-2-one

Crystal data

C4H8N2O	F(000) = 216
Mr = 100.12	Dx = 1.321 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 1593 reflections
a = 7.5746 (11) Å	θ = 3.0–31.6°
b = 9.3984 (13) Å	µ = 0.10 mm^−1
c = 7.9482 (11) Å	T = 298 K
β = 117.139 (2)°	Block, colorless
V = 503.53 (12) Å^3	0.38 × 0.30 × 0.10 mm
Z = 4

Data collection

Bruker SMART APEX diffractometer	888 independent reflections
Radiation source: fine-focus sealed tube	712 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.092
ω scans	θmax = 25.0°, θmin = 3.0°
Absorption correction: ψ scan (Blessing, 1995)	h = −9→9
Tmin = 0.94, Tmax = 0.99	k = −11→11
3853 measured reflections	l = −9→9

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)] = 0.070	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.161	H-atom parameters constrained
S = 1.16	w = 1/[σ^2(Fo^2) + (0.0535P)^2 + 0.1874P] where P = (Fo^2 + 2Fc^2)/3
888 reflections	(Δ/σ)max < 0.001
65 parameters	Δρmax = 0.14 e Å^−3
0 restraints	Δρmin = −0.18 e Å^−3

Special details

Experimental. Add this here

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
O1	0.7224 (3)	1.23376 (17)	−0.0327 (3)	0.0607 (7)
C1	0.7478 (4)	1.1137 (3)	0.0358 (4)	0.0422 (7)
N2	0.7386 (4)	0.9918 (2)	−0.0542 (3)	0.0570 (8)
C2	0.6997 (5)	0.9812 (3)	−0.2483 (4)	0.0610 (9)
H2A	0.6795	1.0746	−0.3028	0.092*
H2B	0.5829	0.9247	−0.3170	0.092*
H2C	0.8107	0.9371	−0.2550	0.092*
C3	0.7750 (4)	0.8699 (3)	0.0645 (4)	0.0565 (8)
H3A	0.8956	0.8215	0.0827	0.068*
H3B	0.6650	0.8035	0.0114	0.068*
C4	0.7961 (4)	0.9324 (3)	0.2486 (4)	0.0556 (8)
H4A	0.6873	0.9032	0.2734	0.067*
H4B	0.9206	0.9043	0.3541	0.067*
N5	0.7908 (4)	1.0826 (2)	0.2151 (3)	0.0601 (8)
H5A	0.8129	1.1459	0.3007	0.072*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.1007 (18)	0.0342 (11)	0.0614 (13)	0.0035 (10)	0.0492 (13)	0.0068 (9)
C1	0.0468 (16)	0.0392 (14)	0.0435 (15)	−0.0003 (11)	0.0232 (13)	−0.0008 (11)
N2	0.090 (2)	0.0353 (12)	0.0456 (14)	0.0022 (11)	0.0304 (14)	−0.0031 (9)
C2	0.079 (2)	0.0567 (19)	0.0485 (18)	−0.0074 (15)	0.0303 (17)	−0.0119 (13)
C3	0.067 (2)	0.0361 (15)	0.067 (2)	0.0078 (13)	0.0305 (17)	0.0036 (12)
C4	0.065 (2)	0.0481 (16)	0.0527 (17)	0.0075 (14)	0.0256 (15)	0.0124 (13)
N5	0.101 (2)	0.0390 (13)	0.0485 (14)	0.0025 (12)	0.0414 (14)	−0.0005 (10)

Geometric parameters (Å, º)

O1—C1	1.229 (3)	C3—C4	1.516 (4)
C1—N2	1.336 (3)	C3—H3A	0.9700
C1—N5	1.341 (3)	C3—H3B	0.9700
N2—C3	1.429 (3)	C4—N5	1.434 (4)
N2—C2	1.436 (3)	C4—H4A	0.9700
C2—H2A	0.9600	C4—H4B	0.9700
C2—H2B	0.9600	N5—H5A	0.8600
C2—H2C	0.9600
O1—C1—N2	126.2 (2)	C4—C3—H3A	111.1
O1—C1—N5	125.7 (2)	N2—C3—H3B	111.1
N2—C1—N5	108.1 (2)	C4—C3—H3B	111.1
C1—N2—C3	112.7 (2)	H3A—C3—H3B	109.1
C1—N2—C2	124.8 (2)	N5—C4—C3	102.7 (2)
C3—N2—C2	122.5 (2)	N5—C4—H4A	111.2
N2—C2—H2A	109.5	C3—C4—H4A	111.2
N2—C2—H2B	109.5	N5—C4—H4B	111.2
H2A—C2—H2B	109.5	C3—C4—H4B	111.2
N2—C2—H2C	109.5	H4A—C4—H4B	109.1
H2A—C2—H2C	109.5	C1—N5—C4	112.6 (2)
H2B—C2—H2C	109.5	C1—N5—H5A	123.7
N2—C3—C4	103.3 (2)	C4—N5—H5A	123.7
N2—C3—H3A	111.1
C1—N2—C3—C4	3.9 (4)	C4—N5—C1—N2	−5.0 (4)
N2—C3—C4—N5	−6.2 (3)	N5—C1—N2—C3	0.4 (4)
C3—C4—N5—C1	7.1 (4)