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The principal determinants of packing in crystals of the title compound, C12H10O2, which has crystallographically imposed inversion symmetry, are interactions between the alkyne H atoms and the methoxy O atoms [H...O = 2.39 (1) Å].

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103027124/gd1290sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103027124/gd1290Isup2.hkl
Contains datablock I

CCDC reference: 231076

Comment top

Alkyne H atoms are frequently described as exhibiting acid characteristics; recent accurate studies of aromatic alkyne derivatives have demonstrated interactions between such H atoms and other electron-rich entities in crystal lattices that might come under the umbrella of 'hydrogen bonding'. Thus low-temperature structure determinations of 1,4-diethynyl- and 1,3,5-triethynyl-benzenes show that interactions between such H atoms and the triple bonds of adjacent molecules may be considerable determinants of crystal packing, while in ethynylbenzene, in addition, interactions with the aromatic π-system are found (Weiss et al., 1997). In systems containing aromatic nitro groups, the interactions are found to take place with the nitro substituents (Robinson et al., 1999). Having on our shelves a crystalline sample of the title compound, we were interested in ascertaining the nature of any such interactions that might occur therein, in view of the frequent association of the methoxy O atoms with putative positive charges, and so have determined its crystal structure.

At ca 150 K, the crystals diffracted nicely, yielding extensive good quality data, with a concomitantly precise result, enabling definitive location of all H atoms in the X-ray sense. The asymmetric unit contains one-half of the centrosymmetric molecule, in space group P21/c. The aromatic ring is a remarkably regular hexagon; the exocyclic angles at the pendant O atom display the usual asymmetry associated with methoxy substituents, the methoxy C atom being approximately coplanar with the sequence C1–C3 [deviation 0.054 (5) Å] and, as usual, enclosing the larger of the exocyclic angles. The C—H distances fall into three classes, viz. (aliphatic) methyl C—H > aromatic > ethynyl. The essentially planar molecules pack in a staggered herringbone fashion as viewed along a; the closest intermolecular contacts are found between the ethynyl H and the methoxy O atoms (Table 1)

In the course of submission of this paper, we were advised of a parallel contemporary study of this compound, among a broader array of related species, the compound in question being the subject of a room-temperature X-ray powder diffraction study using only 243 reflections, giving R = 0.045 (Khan et al., 2003). While the results of the two studies are harmonious, the present low-temperature single-crystal study provides a degree of precision inaccessible in the powder work.

Experimental top

The title compound was obtained by a conventional route, by coupling 1,4-diiodo-2,5-dimethoxybenzene (Ramos et al., 2001) with HC CSiMe3 in the presence of a Pd(PPh3)4/CuI catalyst (Dirk et al., 2001), followed by proto-desilylation of the resulting 1,4-(SiMe3C C)2-2,5-(MeO)2C6H2 (Pelter & James, 2000), and was identified by comparison of the IR and NMR data with literature values. Crystals suitable for X-ray diffraction were obtained from a CDCl3/methanol mixture.

Refinement top

H atoms were located from difference Fourier maps and placed at idealized positions (C—H = 0.95 Å), and their positional and U values were refined.

Structure description top

Alkyne H atoms are frequently described as exhibiting acid characteristics; recent accurate studies of aromatic alkyne derivatives have demonstrated interactions between such H atoms and other electron-rich entities in crystal lattices that might come under the umbrella of 'hydrogen bonding'. Thus low-temperature structure determinations of 1,4-diethynyl- and 1,3,5-triethynyl-benzenes show that interactions between such H atoms and the triple bonds of adjacent molecules may be considerable determinants of crystal packing, while in ethynylbenzene, in addition, interactions with the aromatic π-system are found (Weiss et al., 1997). In systems containing aromatic nitro groups, the interactions are found to take place with the nitro substituents (Robinson et al., 1999). Having on our shelves a crystalline sample of the title compound, we were interested in ascertaining the nature of any such interactions that might occur therein, in view of the frequent association of the methoxy O atoms with putative positive charges, and so have determined its crystal structure.

At ca 150 K, the crystals diffracted nicely, yielding extensive good quality data, with a concomitantly precise result, enabling definitive location of all H atoms in the X-ray sense. The asymmetric unit contains one-half of the centrosymmetric molecule, in space group P21/c. The aromatic ring is a remarkably regular hexagon; the exocyclic angles at the pendant O atom display the usual asymmetry associated with methoxy substituents, the methoxy C atom being approximately coplanar with the sequence C1–C3 [deviation 0.054 (5) Å] and, as usual, enclosing the larger of the exocyclic angles. The C—H distances fall into three classes, viz. (aliphatic) methyl C—H > aromatic > ethynyl. The essentially planar molecules pack in a staggered herringbone fashion as viewed along a; the closest intermolecular contacts are found between the ethynyl H and the methoxy O atoms (Table 1)

In the course of submission of this paper, we were advised of a parallel contemporary study of this compound, among a broader array of related species, the compound in question being the subject of a room-temperature X-ray powder diffraction study using only 243 reflections, giving R = 0.045 (Khan et al., 2003). While the results of the two studies are harmonious, the present low-temperature single-crystal study provides a degree of precision inaccessible in the powder work.

Computing details top

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Siemens, 1995); data reduction: Xtal3.5 (Hall et al., 1995); program(s) used to solve structure: Xtal3.5; program(s) used to refine structure: CRYLSQ in Xtal3.5; molecular graphics: Xtal3.5; software used to prepare material for publication: BONDLA and CIFIO in Xtal3.5.

Figures top
[Figure 1] Fig. 1. Unit-cell contents of the title compound, projected down b. [Symmetry codes: (i) 1 - x,1/2 + y,1/2 - z, (ii) 1 - x,y - 1/2,1/2 - z.]
[Figure 2] Fig. 2. Unit-cell contents of the title compound, projected down a. [Symmetry codes: (i) 1 - x,1/2 + y,1/2 - z.]
(I) top
Crystal data top
C12H10O2F(000) = 196
Mr = 186.21Dx = 1.257 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -p 2ybcCell parameters from 3004 reflections
a = 9.111 (1) Åθ = 2.8–34.6°
b = 5.9921 (7) ŵ = 0.09 mm1
c = 9.408 (1) ÅT = 150 K
β = 106.710 (2)°Plate, colourless
V = 491.93 (9) Å30.35 × 0.16 × 0.08 mm
Z = 2
Data collection top
Bruker SMART CCD
diffractometer
2574 independent reflections
Radiation source: sealed tube1957 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.025
ω scansθmax = 37.4°, θmin = 2.3°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 1514
Tmin = 0.77, Tmax = 0.93k = 1010
10271 measured reflectionsl = 1616
Refinement top
Refinement on FPrimary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.044Hydrogen site location: difference Fourier map
wR(F2) = 0.05All H-atom parameters refined
S = 1.03 w = 1/[σ2(F) + 0.0003F2]
1957 reflections(Δ/σ)max = 0.005
84 parametersΔρmax = 0.53 e Å3
0 restraintsΔρmin = 0.21 e Å3
0 constraints
Crystal data top
C12H10O2V = 491.93 (9) Å3
Mr = 186.21Z = 2
Monoclinic, P21/cMo Kα radiation
a = 9.111 (1) ŵ = 0.09 mm1
b = 5.9921 (7) ÅT = 150 K
c = 9.408 (1) Å0.35 × 0.16 × 0.08 mm
β = 106.710 (2)°
Data collection top
Bruker SMART CCD
diffractometer
2574 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1957 reflections with I > 2σ(I)
Tmin = 0.77, Tmax = 0.93Rint = 0.025
10271 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0440 restraints
wR(F2) = 0.05All H-atom parameters refined
S = 1.03Δρmax = 0.53 e Å3
1957 reflectionsΔρmin = 0.21 e Å3
84 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.12902 (9)0.11388 (15)0.08619 (9)0.0184 (3)
C110.26167 (10)0.22987 (15)0.17564 (10)0.0206 (3)
C120.37230 (11)0.32442 (18)0.25064 (11)0.0253 (4)
C20.14706 (9)0.07129 (15)0.00091 (9)0.0185 (3)
O20.29445 (7)0.12925 (12)0.01094 (7)0.0232 (3)
C210.31587 (11)0.30991 (18)0.08093 (11)0.0251 (4)
C30.01834 (9)0.18351 (15)0.08506 (9)0.0199 (3)
H120.4603 (18)0.398 (3)0.3090 (17)0.043 (4)*
H21a0.4284 (16)0.323 (2)0.0608 (15)0.032 (3)*
H21b0.2691 (16)0.275 (2)0.1866 (15)0.030 (3)*
H21c0.2737 (14)0.450 (2)0.0564 (14)0.028 (3)*
H30.0288 (14)0.312 (2)0.1451 (14)0.025 (3)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0136 (3)0.0204 (4)0.0185 (3)0.0000 (3)0.0003 (2)0.0007 (3)
C110.0168 (3)0.0220 (4)0.0214 (4)0.0011 (3)0.0028 (3)0.0002 (3)
C120.0189 (4)0.0276 (4)0.0266 (4)0.0024 (3)0.0020 (3)0.0029 (3)
C20.0125 (3)0.0219 (4)0.0190 (3)0.0020 (3)0.0011 (2)0.0000 (3)
O20.0132 (2)0.0290 (3)0.0250 (3)0.0036 (2)0.0019 (2)0.0053 (3)
C210.0214 (4)0.0273 (4)0.0264 (4)0.0056 (3)0.0068 (3)0.0025 (3)
C30.0151 (3)0.0217 (4)0.0205 (3)0.0011 (3)0.0012 (2)0.0034 (3)
Geometric parameters (Å, º) top
C1—C111.4377 (11)C2—C31.3914 (11)
C1—C21.4063 (13)O2—C211.4331 (13)
C1—C3i1.4031 (12)C21—H21a0.991 (15)
C11—C121.1941 (12)C21—H21b0.985 (13)
C12—H120.940 (14)C21—H21c0.979 (14)
C2—O21.3638 (11)C3—H30.974 (14)
C11—C1—C2119.93 (8)O2—C21—H21a104.9 (8)
C11—C1—C3i120.15 (8)O2—C21—H21b110.7 (8)
C2—C1—C3i119.92 (7)O2—C21—H21c112.1 (9)
C1—C11—C12179.39 (11)H21a—C21—H21b109.4 (12)
C11—C12—H12179.1 (11)H21a—C21—H21c110.0 (11)
C1—C2—O2115.83 (7)H21b—C21—H21c109.6 (11)
C1—C2—C3119.71 (8)C2—C3—H3120.8 (7)
O2—C2—C3124.45 (8)C2—C3—C1i120.36 (8)
C2—O2—C21116.92 (7)H3—C3—C1i118.9 (7)
Symmetry code: (i) x, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C12—H12···O2ii0.94 (1)2.39 (1)3.227 (1)148 (1)
Symmetry code: (ii) x+1, y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC12H10O2
Mr186.21
Crystal system, space groupMonoclinic, P21/c
Temperature (K)150
a, b, c (Å)9.111 (1), 5.9921 (7), 9.408 (1)
β (°) 106.710 (2)
V3)491.93 (9)
Z2
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.35 × 0.16 × 0.08
Data collection
DiffractometerBruker SMART CCD
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.77, 0.93
No. of measured, independent and
observed [I > 2σ(I)] reflections
10271, 2574, 1957
Rint0.025
(sin θ/λ)max1)0.855
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.05, 1.03
No. of reflections1957
No. of parameters84
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.53, 0.21

Computer programs: SMART (Siemens, 1995), SAINT (Siemens, 1995), Xtal3.5 (Hall et al., 1995), CRYLSQ in Xtal3.5, BONDLA and CIFIO in Xtal3.5.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C12—H12···O2i0.94 (1)2.39 (1)3.227 (1)148 (1)
Symmetry code: (i) x+1, y+1/2, z+1/2.
 

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