Acta Cryst. (2008). E64, o1562 [ doi:10.1107/S1600536808022381 ]
A new orthorhombic polymorph of terephthalaldehyde, C8H6O2, with a melting point of 372 K, has been obtained by recrystallization from ethanol. At room temperature, the crystals transform into the well known monoclinic form, with a melting point of 389 K. The crystal structure of the monoclinic form involves C-H
O hydrogen bonds, but no such bonds are observed in the orthorhombic form. The molecule is planar.
All H atoms were initially located in a difference Fourier map and then included with constrained bond lengths and isotropic displacement parameters: C—H=0.93Å and Uiso(H)=1.2Ueq(C) for H atoms.
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
![[Figure 1]](./bq2093fig1thm.gif)
| Fig. 1. The molecular structure of (I) with 50% probability displacement ellipsoids (arbitrary spheres for H atoms). |
![[Figure 2]](./bq2093fig2thm.gif)
| Fig. 2. The packing of the molecules, viewed down the b axis. |
| C8H6O2 | F000 = 280 |
| Mr = 134.13 | Dx = 1.334 Mg m−3 |
| Orthorhombic, Pca21 | Mo Kα radiation λ = 0.71073 Å |
| Hall symbol: P 2c -2ac | Cell parameters from 1070 reflections |
| a = 12.8811 (5) Å | θ = 3.1–23.5º |
| b = 3.8933 (3) Å | µ = 0.10 mm−1 |
| c = 13.3202 (9) Å | T = 295 (2) K |
| V = 668.01 (7) Å3 | Block, colorless |
| Z = 4 | 0.20 × 0.10 × 0.10 mm |
| Bruker SMART 4K CCD area-detector diffractometer | 563 reflections with I > 2σ(I) |
| Radiation source: fine-focus sealed tube | Rint = 0.030 |
| Monochromator: graphite | θmax = 25.5º |
| T = 295(2) K | θmin = 3.1º |
| φ and ω scans | h = −15→12 |
| Absorption correction: none | k = −4→4 |
| 3959 measured reflections | l = −16→15 |
| 653 independent reflections |
| 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)] = 0.042 | H-atom parameters constrained |
| wR(F2) = 0.112 | w = 1/[σ2(Fo2) + (0.0755P)2 + 0.0133P] where P = (Fo2 + 2Fc2)/3 |
| S = 1.04 | (Δ/σ)max = 0.014 |
| 653 reflections | Δρmax = 0.16 e Å−3 |
| 91 parameters | Δρmin = −0.10 e Å−3 |
| 1 restraint | Extinction correction: none |
| Primary atom site location: structure-invariant direct methods |
| C8H6O2 | V = 668.01 (7) Å3 |
| Mr = 134.13 | Z = 4 |
| Orthorhombic, Pca21 | Mo Kα |
| a = 12.8811 (5) Å | µ = 0.10 mm−1 |
| b = 3.8933 (3) Å | T = 295 (2) K |
| c = 13.3202 (9) Å | 0.20 × 0.10 × 0.10 mm |
| Bruker SMART 4K CCD area-detector diffractometer | 653 independent reflections |
| Absorption correction: none | 563 reflections with I > 2σ(I) |
| 3959 measured reflections | Rint = 0.030 |
| R[F2 > 2σ(F2)] = 0.042 | H-atom parameters constrained |
| wR(F2) = 0.112 | Δρmax = 0.16 e Å−3 |
| S = 1.04 | Δρmin = −0.10 e Å−3 |
| 653 reflections | Absolute structure: ? |
| 91 parameters | Flack parameter: ? |
| 1 restraint | Rogers parameter: ? |
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. |
| x | y | z | Uiso*/Ueq | ||
| C1 | 0.8164 (2) | 0.3463 (7) | 0.2145 (2) | 0.0509 (7) | |
| C2 | 0.9236 (2) | 0.3850 (7) | 0.2147 (3) | 0.0545 (7) | |
| H2 | 0.9566 | 0.4847 | 0.1599 | 0.065* | |
| C3 | 0.9315 (2) | 0.1279 (7) | 0.3776 (2) | 0.0515 (7) | |
| C4 | 0.8239 (2) | 0.0894 (7) | 0.3770 (3) | 0.0547 (7) | |
| H4 | 0.7907 | −0.0106 | 0.4316 | 0.066* | |
| C5 | 0.7668 (2) | 0.1993 (6) | 0.2955 (3) | 0.0543 (7) | |
| H5 | 0.6950 | 0.1744 | 0.2953 | 0.065* | |
| C6 | 0.9805 (2) | 0.2776 (7) | 0.2951 (3) | 0.0547 (6) | |
| H6 | 1.0523 | 0.3040 | 0.2949 | 0.066* | |
| C7 | 0.7563 (4) | 0.4635 (8) | 0.1269 (4) | 0.0707 (10) | |
| H7 | 0.7934 | 0.5547 | 0.0733 | 0.085* | |
| C8 | 0.9916 (3) | 0.0084 (8) | 0.4657 (4) | 0.0627 (9) | |
| H8 | 0.9550 | −0.0874 | 0.5190 | 0.075* | |
| O1 | 0.6637 (2) | 0.4514 (7) | 0.1187 (3) | 0.0930 (10) | |
| O2 | 1.0834 (2) | 0.0266 (7) | 0.4731 (4) | 0.0876 (9) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| C1 | 0.0535 (16) | 0.0494 (14) | 0.0498 (17) | 0.0041 (11) | 0.0057 (14) | −0.0068 (13) |
| C2 | 0.0564 (18) | 0.0551 (15) | 0.0520 (17) | 0.0022 (13) | 0.0123 (15) | 0.0015 (15) |
| C3 | 0.0547 (16) | 0.0509 (14) | 0.0490 (17) | −0.0008 (12) | 0.0064 (15) | −0.0078 (13) |
| C4 | 0.0593 (19) | 0.0573 (14) | 0.0476 (17) | −0.0067 (14) | 0.0140 (16) | 0.0002 (14) |
| C5 | 0.0463 (13) | 0.0570 (14) | 0.0595 (15) | −0.0016 (12) | 0.0102 (17) | −0.0083 (14) |
| C6 | 0.0448 (13) | 0.0582 (14) | 0.0610 (15) | −0.0003 (12) | 0.0043 (18) | −0.0008 (14) |
| C7 | 0.071 (2) | 0.077 (2) | 0.063 (3) | 0.0121 (16) | −0.006 (2) | −0.0016 (18) |
| C8 | 0.067 (2) | 0.0704 (19) | 0.0508 (19) | 0.0030 (13) | 0.009 (2) | 0.0003 (14) |
| O1 | 0.075 (2) | 0.129 (2) | 0.075 (2) | 0.0162 (14) | −0.0158 (19) | −0.0026 (18) |
| O2 | 0.0617 (17) | 0.125 (2) | 0.0761 (19) | 0.0064 (12) | −0.0077 (16) | 0.0074 (15) |
| C1—C5 | 1.378 (4) | C4—C5 | 1.379 (5) |
| C1—C2 | 1.389 (4) | C4—H4 | 0.9300 |
| C1—C7 | 1.473 (6) | C5—H5 | 0.9300 |
| C2—C6 | 1.363 (5) | C6—H6 | 0.9300 |
| C2—H2 | 0.9300 | C7—O1 | 1.199 (5) |
| C3—C4 | 1.393 (4) | C7—H7 | 0.9300 |
| C3—C6 | 1.395 (4) | C8—O2 | 1.188 (4) |
| C3—C8 | 1.482 (6) | C8—H8 | 0.9300 |
| C5—C1—C2 | 120.2 (3) | C1—C5—C4 | 119.9 (3) |
| C5—C1—C7 | 120.4 (3) | C1—C5—H5 | 120.1 |
| C2—C1—C7 | 119.4 (3) | C4—C5—H5 | 120.1 |
| C6—C2—C1 | 120.2 (3) | C2—C6—C3 | 120.2 (2) |
| C6—C2—H2 | 119.9 | C2—C6—H6 | 119.9 |
| C1—C2—H2 | 119.9 | C3—C6—H6 | 119.9 |
| C4—C3—C6 | 119.4 (3) | O1—C7—C1 | 125.6 (5) |
| C4—C3—C8 | 119.4 (3) | O1—C7—H7 | 117.2 |
| C6—C3—C8 | 121.2 (3) | C1—C7—H7 | 117.2 |
| C5—C4—C3 | 120.1 (3) | O2—C8—C3 | 124.5 (4) |
| C5—C4—H4 | 120.0 | O2—C8—H8 | 117.7 |
| C3—C4—H4 | 120.0 | C3—C8—H8 | 117.7 |
| C5—C1—C2—C6 | 0.1 (4) | C1—C2—C6—C3 | 0.0 (4) |
| C7—C1—C2—C6 | −179.9 (3) | C4—C3—C6—C2 | 0.0 (4) |
| C6—C3—C4—C5 | −0.2 (4) | C8—C3—C6—C2 | 179.9 (3) |
| C8—C3—C4—C5 | 180.0 (3) | C5—C1—C7—O1 | 1.8 (5) |
| C2—C1—C5—C4 | −0.2 (4) | C2—C1—C7—O1 | −178.2 (3) |
| C7—C1—C5—C4 | 179.7 (3) | C4—C3—C8—O2 | 179.2 (3) |
| C3—C4—C5—C1 | 0.2 (4) | C6—C3—C8—O2 | −0.6 (5) |
Britton, D. (1998). J. Chem. Crystallogr. 28, 601–604.
Bruker (2001). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.
Terephthalaldehyde, (I), is a simple aromatic compound used in organic synthesis. It is known as a white substance, slightly soluble in water, with a melting point of 389 K. To the best of our knowledge, the only packing information of (I) in the solid state comes from the work of Britton (Britton, 1998), who investigated the intermolecular C—H···O arrangement in the structure of terephthalaldehyde and the crystals suitable for diffraction were obtained by recrystallization from an acetone/ethyl ether mixture.
A new polymorphic form of (I) has been obtained serendipitously during cocrystallization of pyridine and terephthalaldehyde from ethanol (Fig. 1). Flat needles which precipitated first from the solution had a melting point of 372 K and were identified as a new polymorphic form of (I) by X-ray crystallography. At room temperature, the crystals transform into the well known monoclinic form, with a melting point of 389 K. The crystal structure of the monoclinic form involves C—H···O hydrogen bonds but no such bonds are observed in the orthorhombic form (Fig. 2).