Buy article online - an online subscription or single-article purchase is required to access this article.
Acetic anhydride (ethanoic anhydride), (CH3CO)2O, is a widely used acetylation reagent in organic synthesis. The crystal and molecular structure, as determined by single-crystal X-ray analysis at 100 K, is reported for the first time. A crystal of the title compound (m.p. 200 K) suitable for X-ray diffraction was grown from the melt at low temperature. The title compound crystallizes in the orthorhombic space group Pbcn, with Z = 4. In the crystal, the molecule adopts an exact C2-symmetric conformation about a crystallographic twofold axis. The molecules are densely packed. Two of the methyl H atoms form short intermolecular contacts to a neighbouring carbonyl O atom, which can be viewed as weak hydrogen bonds.
Supporting information
CCDC reference: 1505908
Data collection: APEX2 (Bruker, 2013); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 2014); software used to prepare material for publication: enCIFer (Allen et al., 2004).
Crystal data top
C4H6O3 | Dx = 1.346 Mg m−3 |
Mr = 102.09 | Cu Kα radiation, λ = 1.54178 Å |
Orthorhombic, Pbcn | Cell parameters from 1147 reflections |
a = 8.0707 (14) Å | θ = 5.5–41.1° |
b = 7.8733 (13) Å | µ = 1.01 mm−1 |
c = 7.9305 (13) Å | T = 100 K |
V = 503.93 (15) Å3 | Cylinder, colourless |
Z = 4 | 1.32 × 0.50 × 0.50 mm |
F(000) = 216 | |
Data collection top
Bruker AXS X8 Proteum diffractometer | 452 independent reflections |
Radiation source: 0.2 x 2 mm focus rotating anode | 445 reflections with I > 2σ(I) |
MONTEL graded multilayer optic monochromator | Rint = 0.051 |
Detector resolution: 16.67 pixels mm-1 | θmax = 67.4°, θmin = 7.9° |
φ– and ω–scans | h = −9→9 |
Absorption correction: gaussian (SADABS; Bruker, 2012) | k = −9→9 |
Tmin = 0.472, Tmax = 0.669 | l = −7→8 |
19642 measured reflections | |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.025 | H-atom parameters constrained |
wR(F2) = 0.064 | w = 1/[σ2(Fo2) + (0.0276P)2 + 0.1605P] where P = (Fo2 + 2Fc2)/3 |
S = 1.09 | (Δ/σ)max < 0.001 |
452 reflections | Δρmax = 0.16 e Å−3 |
35 parameters | Δρmin = −0.14 e Å−3 |
0 restraints | Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.012 (2) |
Special details top
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 0.14484 (9) | 0.04403 (9) | 0.34929 (9) | 0.0280 (3) | |
O2 | 0.0000 | 0.26741 (12) | 0.2500 | 0.0253 (3) | |
C1 | 0.08205 (11) | 0.17820 (12) | 0.37607 (12) | 0.0204 (3) | |
C2 | 0.08774 (13) | 0.27697 (12) | 0.53580 (13) | 0.0245 (3) | |
H2A | 0.1315 | 0.2051 | 0.6263 | 0.037* | |
H2B | −0.0243 | 0.3148 | 0.5652 | 0.037* | |
H2C | 0.1597 | 0.3761 | 0.5211 | 0.037* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0304 (5) | 0.0292 (5) | 0.0246 (5) | 0.0064 (3) | −0.0029 (3) | −0.0002 (3) |
O2 | 0.0345 (6) | 0.0211 (5) | 0.0203 (6) | 0.000 | −0.0097 (4) | 0.000 |
C1 | 0.0187 (5) | 0.0230 (5) | 0.0195 (6) | −0.0035 (4) | −0.0005 (4) | 0.0041 (4) |
C2 | 0.0303 (6) | 0.0247 (6) | 0.0186 (6) | −0.0046 (4) | −0.0021 (4) | 0.0011 (4) |
Geometric parameters (Å, º) top
O1—C1 | 1.1907 (12) | C2—H2A | 0.9800 |
O2—C1i | 1.3897 (11) | C2—H2B | 0.9800 |
O2—C1 | 1.3897 (11) | C2—H2C | 0.9800 |
C1—C2 | 1.4871 (14) | | |
| | | |
C1i—O2—C1 | 119.29 (10) | C1—C2—H2B | 109.5 |
O1—C1—O2 | 121.52 (9) | H2A—C2—H2B | 109.5 |
O1—C1—C2 | 127.06 (9) | C1—C2—H2C | 109.5 |
O2—C1—C2 | 111.30 (8) | H2A—C2—H2C | 109.5 |
C1—C2—H2A | 109.5 | H2B—C2—H2C | 109.5 |
| | | |
C1i—O2—C1—O1 | 32.13 (7) | C1i—O2—C1—C2 | −151.49 (8) |
Symmetry code: (i) −x, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2A···O1ii | 0.98 | 2.64 | 3.5750 (13) | 159 |
C2—H2C···O1iii | 0.98 | 2.47 | 3.3567 (13) | 151 |
Symmetry codes: (ii) x, −y, z+1/2; (iii) −x+1/2, y+1/2, z. |
Selected bond lengths (Å) and angles (°) for (I) in the crystal (X-ray) and
for the [sp,ssp] conformor the gas phase, as determined by
electron diffraction (ED) analysis and B3LYP/cc-pVTZ calculations. top | X-ray | ED | B3LYP/cc-pVTZ |
O1—C1 | 1.1907 (12) | 1.182 (3) | 1.191 |
O2—C1i | 1.3897 (11) | 1.370 (15) | 1.395 |
O2—C1 | 1.3897 (11) | 1.370 (15) | 1.395 |
C1—C2 | 1.4871 (14) | 1.489 (2) | 1.500 |
C1i—O2—C1 | 119.29 (10) | 116.5 (20) | 120.98 |
O1—C1—O2 | 121.52 (9) | 124.8 (20) | 123.04 |
O1—C1—C2 | 127.06 (9) | - | 126.94 |
O2—C1—C2 | 111.30 (8) | 114.6 (23) | 109.97 |
Geometric parameters derived from ED analysis B3LYP/cc-pVTZ calculations were
taken from Wu et al. (2000).
Symmetry code: (i) -x, y, -z+1/2. |
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
support@iucr.org for assistance.