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A low-temperature redetermination of met­aldehyde

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aChristopher Ingold Laboratory, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, England
*Correspondence e-mail: a.hulme@ucl.ac.uk

(Received 23 February 2005; accepted 28 February 2005; online 4 March 2005)

A low-temperature redetermination of met­aldehyde (systematic name: 2,4,6,8-tetra­methyl-1,3,5,7-tetroxocane), (CH3–CHO)4 or C8H16O4, is reported, 69 years after the original determination [Pauling & Carpenter (1936[Pauling, L. & Carpenter, D. C. (1936). J. Am. Chem. Soc. 58, 1274-1278.]). J. Am. Chem. Soc. 58, 1274–1278]. Met­aldehyde crystallizes in the space group I4. The asymmetric unit contains one quarter of a mol­ecule and the complete mol­ecule is generated by the fourfold rotation axis.

Comment

The structure of met­aldehyde, or 2,4,6,8-tetra­methyl-1,3,5,7-tetroxocane, (I[link]), was first reported by Pauling & Carpenter (1936[Pauling, L. & Carpenter, D. C. (1936). J. Am. Chem. Soc. 58, 1274-1278.]), using photographic methods. In the intervening 69 years, no further single-crystal determination of this compound has been deposited with the Cambridge Structural Database (Version of February 2005; Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]). We now report a low-temperature redetermination of this structure using a modern area-detector-equipped diffractometer, with all H-atom positions determined from the electron-density map.[link]

[Scheme 1]

Crystals of met­aldehyde were grown by chance while attempting a recrystallization of 5-fluoro­cytosine from acet­aldehyde. Under the conditions of the recrystallization experiment, four acet­aldehyde mol­ecules cyclized to form met­aldehyde and this subsequently crystallized from solution.

The crystals grew as long needles. Attempts to cut a crystal perpendicular to the axis of the needle led to the shattering of the entire crystal. Therefore, a large complete needle was mounted, with no attempt made to reduce its size. This crystal measured approximately 1.25 mm in the direction of the long axis of the needle.

Met­aldehyde (Fig. 1[link]) comprises a tetramer of CH3CHO units, with only one unit present in the asymmetric unit. The fourfold rotation axis generates the complete mol­ecule and two mol­ecules are present in the unit cell. There are no conventional strong hydrogen bonds in the structure, due to the lack of a hydrogen-bond donor. One weak C2—H2⋯O1iv hydrogen-bond interaction is present within the accepted range for C—H⋯O bonds (Desiraju, 1996[Desiraju, G. R. (1996). Acc. Chem. Res. 29, 441-449.]) [C2⋯O1 = 3.631 (2) Å and C2—H2⋯O1iv = 164 (2)°; symmetry code: (iv) [{3 \over 2}] − y, [{1 \over 2}] + x, z − [{1 \over 2}] ].

The mol­ecule in the body-centred position of the unit cell forms four C—H⋯O bonds, one to each of the four mol­ecules located at the unit-cell vertices with z = 0. It also forms four O⋯H—C bonds, one to each of the four mol­ecules at the vertices of the unit cell with z = 1 (Fig. 2[link]). The overall motif is a three-dimensional hydrogen-bonded network (Fig. 3[link]). The mol­ecules stack directly upon one another to form columns, parallel to the c axis. As described in the original paper (Pauling & Carpenter, 1936[Pauling, L. & Carpenter, D. C. (1936). J. Am. Chem. Soc. 58, 1274-1278.]), there may be electrostatic interactions between the adjacent members of the column, as each mol­ecule has a partially negatively charged face (comprising the four O atoms in the ring), and a partially positively charged face (comprising the four H atoms bonded to the C atoms in the ring). The distance between the plane of the four O1 atoms in one mol­ecule and the plane of the four C1 atoms in the adjacent mol­ecule in the column is 3.51 Å.

The largest geometrical difference between this redetermination and the original structure is in the bond angles about C1. In the original determination, the angles about C1 were constrained to the tetrahedral bond angle, whereas in the structure reported here, these angles deviate by up to 2.5° from the tetrahedral angle [C2—C1—O1 = 106.9 (1)°, C2—C1—O1iii = 106.7 (1)° and O1—C1—O1iii = 112.0 (1)°; symmetry code: (iii) y − 1, 1 − x, z]. These deviations may be due to changes in the molecular conformation with temperature, rather than the use of constraints in the original report.

[Figure 1]
Figure 1
A single mol­ecule of the title compound. Displacement ellipsoids are drawn at the 50% probability level. H atoms are drawn as spheres of arbitrary radii. [Symmetry codes: (i) 1 − y, 1 + x, z; (ii) −x, 2 − y, z; (iii) y − 1, 1 − x, z.]
[Figure 2]
Figure 2
A view inclined to the c axis, showing the C—H⋯O hydrogen bonding as dotted lines. The grey mol­ecules are one unit cell lower than the coloured mol­ecules. The central mol­ecule bonds to the four mol­ecules in the upper plane and the four in the lower plane.
[Figure 3]
Figure 3
View along the a axis, showing the C—H⋯O hydrogen-bonded network. Hydro­gen bonds are shown as dotted lines.

Experimental

Met­aldehyde crystals were produced from an attempt to recrystallize 5-fluoro­cytosine from acet­aldehyde by solvent evaporation at 278 K.

Crystal data
  • C8H16O4

  • Mr = 176.21

  • Tetragonal, I4

  • a = 10.4974 (10) Å

  • c = 4.0967 (7) Å

  • V = 451.44 (10) Å3

  • Z = 2

  • Dx = 1.296 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 1875 reflections

  • θ = 2.7–28.3°

  • μ = 0.10 mm−1

  • T = 150 (2) K

  • Needle, colourless

  • 1.24 × 0.39 × 0.22 mm

Data collection
  • Bruker SMART APEX diffractometer

  • ω rotation with narrow-frame scans

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.883, Tmax = 0.978

  • 1953 measured reflections

  • 314 independent reflections

  • 312 reflections with I > 2σ(I)

  • Rint = 0.017

  • θmax = 28.3°

  • h = −13 → 13

  • k = −13 → 13

  • l = −5 → 5

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.029

  • wR(F2) = 0.073

  • S = 1.08

  • 314 reflections

  • 45 parameters

  • All H-atom parameters refined

  • w = 1/[σ2(Fo2) + (0.0515P)2 + 0.1168P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 0.17 e Å−3

  • Δρmin = −0.18 e Å−3

  • Extinction correction: SHELXL97

  • Extinction coefficient: 0.103 (18)

The quoted transmission factors result from correction for incomplete irradiation of the long needle crystal as well as absorption effects. All H atoms were located in a difference map and were refined isotropically; the range of C—H bond lengths is 0.94 (2)–1.00 (3) Å. Friedel pairs were merged as no significant anomalous scattering effects were observed.

Data collection: SMART (Bruker, 1998[Bruker (1998). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 1998[Bruker (1998). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); molecular graphics: CAMERON (Watkin et al., 1996[Watkin, D. J., Prout, C. K. & Pearce, L. J. (1996). CAMERON. Chemical Crystallography Laboratory, Oxford, England.]); software used to prepare material for publication: SHELXL97.

Supporting information


Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: SHELXL97.

2,4,6,8-tetramethyl-1,3,5,7-tetroxocane top
Crystal data top
C8H16O4Dx = 1.296 Mg m3
Mr = 176.21Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I4Cell parameters from 1875 reflections
Hall symbol: I 4θ = 2.7–28.3°
a = 10.4974 (10) ŵ = 0.10 mm1
c = 4.0967 (7) ÅT = 150 K
V = 451.44 (10) Å3Needle, colourless
Z = 21.24 × 0.39 × 0.22 mm
F(000) = 192
Data collection top
Bruker SMART APEX
diffractometer
314 independent reflections
Radiation source: fine-focus sealed tube312 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.017
ω rotation with narrow frames scansθmax = 28.3°, θmin = 2.7°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 1313
Tmin = 0.883, Tmax = 0.978k = 1313
1953 measured reflectionsl = 55
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.029All H-atom parameters refined
wR(F2) = 0.073 w = 1/[σ2(Fo2) + (0.0515P)2 + 0.1168P]
where P = (Fo2 + 2Fc2)/3
S = 1.08(Δ/σ)max < 0.001
314 reflectionsΔρmax = 0.17 e Å3
45 parametersΔρmin = 0.18 e Å3
1 restraintExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.103 (18)
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
xyzUiso*/Ueq
O10.13979 (8)1.07448 (8)1.0388 (2)0.0199 (3)
C10.15579 (11)0.95252 (11)0.8957 (4)0.0187 (3)
H10.1373 (19)0.9582 (17)0.672 (6)0.019 (4)*
C20.29095 (11)0.91096 (13)0.9674 (5)0.0247 (4)
H20.310 (2)0.831 (2)0.861 (6)0.035 (5)*
H30.352 (2)0.974 (2)0.885 (8)0.041 (6)*
H40.298 (2)0.903 (2)1.211 (7)0.036 (6)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0201 (4)0.0173 (5)0.0222 (5)0.0022 (3)0.0029 (4)0.0015 (4)
C10.0182 (6)0.0177 (5)0.0201 (6)0.0005 (4)0.0019 (5)0.0009 (5)
C20.0184 (6)0.0225 (6)0.0333 (8)0.0021 (4)0.0016 (6)0.0010 (6)
Geometric parameters (Å, º) top
O1—C11.4181 (15)C1—H10.94 (2)
O1—C1i1.4181 (15)C2—H20.96 (2)
C1—O1ii1.4181 (15)C2—H30.98 (2)
C1—C21.5132 (17)C2—H41.00 (3)
C1—O1—C1i116.97 (13)C1—C2—H2111.1 (13)
O1—C1—O1ii112.01 (12)C1—C2—H3110.9 (14)
O1—C1—C2106.92 (10)H2—C2—H3107 (2)
O1ii—C1—C2106.68 (10)C1—C2—H4106.4 (13)
O1—C1—H1108.8 (12)H2—C2—H4111 (2)
O1ii—C1—H1108.8 (11)H3—C2—H4111 (2)
C2—C1—H1113.7 (13)
C1i—O1—C1—O1ii90.06 (16)C1i—O1—C1—C2153.41 (10)
Symmetry codes: (i) y+1, x+1, z; (ii) y1, x+1, z.
 

Acknowledgements

The authors acknowledge the Research Councils UK Basic Technology Programme for supporting `Control and Prediction of the Organic Solid State'. For further information, please visit www.cposs.org.uk.

References

First citationAllen, F. H. (2002). Acta Cryst. B58, 380–388.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
First citationBruker (1998). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationDesiraju, G. R. (1996). Acc. Chem. Res. 29, 441–449.  CrossRef CAS PubMed Web of Science Google Scholar
First citationPauling, L. & Carpenter, D. C. (1936). J. Am. Chem. Soc. 58, 1274–1278.  CAS Google Scholar
First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.  Google Scholar
First citationWatkin, D. J., Prout, C. K. & Pearce, L. J. (1996). CAMERON. Chemical Crystallography Laboratory, Oxford, England.  Google Scholar

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