1-(1H-Imidazol-1-yl)ethanone

The title compound, C₅H₆N₂O, was obtained as a side product during the synthesis of diimidazo[1,5-a;1′,5′-d]pyrazine-5,10-dione. The mol­ecule is almost planar with the acetyl group inclined to the mean plane of the imidazole ring by 1.52 (12)°. In the crystal structure, mol­ecules are linked by C—H...O and C—H...N hydrogen bonds, forming a sheet-like structure.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C)= 0.001 Å
• R factor = 0.037
• wR factor = 0.099
• Data-to-parameter ratio = 14.2

checkCIF/PLATON results

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Computing details

Data collection: X-AREA (Stoe & Cie, 2005); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.

1-(1H-Imidazol-1-yl)ethanone

Crystal data

C5H6N2O	F(000) = 232
Mr = 110.12	Dx = 1.434 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 6792 reflections
a = 7.5263 (8) Å	θ = 2.7–29.6°
b = 7.5835 (10) Å	µ = 0.10 mm^−1
c = 9.0853 (10) Å	T = 173 K
β = 100.361 (8)°	Rod, colourless
V = 510.09 (10) Å^3	0.50 × 0.34 × 0.23 mm
Z = 4

Data collection

Stoe IPDS-2 diffractometer	1208 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.064
Graphite monochromator	θmax = 29.2°, θmin = 3.2°
ω and φ scans	h = −9→10
6541 measured reflections	k = −10→10
1380 independent reflections	l = −11→12

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)] = 0.037	Hydrogen site location: difference Fourier map
wR(F^2) = 0.099	All H-atom parameters refined
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0443P)^2 + 0.1063P] where P = (Fo^2 + 2Fc^2)/3
1380 reflections	(Δ/σ)max = 0.002
97 parameters	Δρmax = 0.31 e Å^−3
0 restraints	Δρmin = −0.18 e Å^−3

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

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	0.54967 (10)	0.09548 (9)	0.27123 (8)	0.0273 (2)
N1	0.73130 (10)	0.00829 (10)	0.48493 (9)	0.0193 (2)
N2	0.90493 (12)	−0.11678 (11)	0.68045 (10)	0.0265 (2)
C1	0.84817 (13)	0.03262 (13)	0.61753 (11)	0.0230 (3)
C2	0.82040 (14)	−0.24598 (13)	0.58337 (12)	0.0242 (3)
C3	0.71450 (13)	−0.17296 (12)	0.46345 (11)	0.0212 (2)
C4	0.64752 (12)	0.13917 (12)	0.38522 (11)	0.0202 (2)
C5	0.69090 (14)	0.32584 (13)	0.43316 (12)	0.0255 (3)
H1	0.8815 (19)	0.1487 (19)	0.6561 (17)	0.033 (4)*
H2	0.8378 (19)	−0.3686 (18)	0.6071 (17)	0.031 (3)*
H3	0.6391 (18)	−0.2203 (18)	0.3790 (17)	0.028 (3)*
H4	0.818 (2)	0.351 (2)	0.4395 (18)	0.041 (4)*
H5	0.626 (2)	0.404 (2)	0.363 (2)	0.041 (4)*
H6	0.668 (2)	0.348 (2)	0.5363 (19)	0.042 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0317 (4)	0.0253 (4)	0.0222 (4)	0.0004 (3)	−0.0022 (3)	−0.0007 (3)
N1	0.0211 (4)	0.0173 (4)	0.0191 (4)	−0.0016 (3)	0.0023 (3)	−0.0011 (3)
N2	0.0295 (4)	0.0224 (4)	0.0248 (4)	0.0001 (3)	−0.0027 (3)	0.0010 (3)
C1	0.0249 (4)	0.0207 (4)	0.0214 (5)	−0.0013 (3)	−0.0011 (4)	−0.0012 (3)
C2	0.0271 (5)	0.0183 (4)	0.0267 (5)	−0.0002 (3)	0.0034 (4)	0.0006 (3)
C3	0.0231 (4)	0.0181 (4)	0.0226 (4)	−0.0025 (3)	0.0046 (3)	−0.0029 (3)
C4	0.0209 (4)	0.0200 (4)	0.0199 (4)	0.0002 (3)	0.0040 (3)	0.0008 (3)
C5	0.0283 (5)	0.0178 (4)	0.0288 (5)	−0.0005 (3)	0.0007 (4)	0.0010 (4)

Geometric parameters (Å, º)

O1—C4	1.2043 (12)	C4—C5	1.4997 (14)
N1—C1	1.3704 (13)	C1—H1	0.964 (15)
N1—C3	1.3909 (12)	C2—H2	0.958 (14)
N1—C4	1.4135 (12)	C3—H3	0.940 (15)
N2—C1	1.3058 (13)	C5—H4	0.967 (15)
N2—C2	1.3931 (14)	C5—H5	0.940 (16)
C2—C3	1.3478 (14)	C5—H6	0.997 (17)
C1—N1—C3	106.51 (8)	N2—C1—H1	126.2 (9)
C1—N1—C4	127.64 (8)	N2—C2—H2	120.8 (9)
C3—N1—C4	125.82 (8)	C3—C2—H2	128.1 (9)
C1—N2—C2	104.88 (9)	N1—C3—H3	121.2 (9)
N1—C1—N2	112.07 (9)	C2—C3—H3	133.3 (9)
N2—C2—C3	111.05 (9)	C4—C5—H4	111.4 (9)
N1—C3—C2	105.49 (8)	C4—C5—H5	109.8 (10)
O1—C4—N1	119.42 (8)	C4—C5—H6	111.5 (9)
O1—C4—C5	125.24 (9)	H4—C5—H5	107.7 (13)
N1—C4—C5	115.34 (8)	H4—C5—H6	104.3 (13)
N1—C1—H1	121.8 (9)	H5—C5—H6	112.0 (14)
C3—N1—C1—N2	−0.20 (11)	C3—N1—C4—O1	1.18 (14)
C4—N1—C1—N2	−178.22 (9)	C3—N1—C4—C5	−178.70 (9)
C1—N1—C3—C2	0.27 (11)	C2—N2—C1—N1	0.04 (11)
C4—N1—C3—C2	178.34 (9)	C1—N2—C2—C3	0.15 (12)
C1—N1—C4—O1	178.83 (9)	N2—C2—C3—N1	−0.26 (12)
C1—N1—C4—C5	−1.05 (14)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···O1^i	0.964 (15)	2.446 (15)	3.3826 (13)	163.9 (12)
C3—H3···N2^ii	0.940 (15)	2.597 (15)	3.5252 (14)	169.7 (12)

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