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The structure of 4′-hydroxy­aceto­phenone, C8H8O2, (1), has been redetermined at 150 K. There are two mol­ecules in the asymmetric unit and the equivalent bond lengths and angles in each mol­ecule are the same. Pairs of independent O—H...O hydrogen-bonded mol­ecules (H...O 1.87 Å) are linked, in turn, by different O—H...O hydrogen bonds (H...O 1.90 Å), through 21 screw axes, to form chains in the c direction.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802015581/cf6199sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536802015581/cf6199Isup2.hkl
Contains datablock I

CCDC reference: 198331

Key indicators

  • Single-crystal X-ray study
  • T = 150 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.034
  • wR factor = 0.087
  • Data-to-parameter ratio = 7.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes

REFLT_03 From the CIF: _diffrn_reflns_theta_max 25.01 From the CIF: _reflns_number_total 1405 Count of symmetry unique reflns 1438 Completeness (_total/calc) 97.71% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 0 Fraction of Friedel pairs measured 0.000 Are heavy atom types Z>Si present no Please check that the estimate of the number of Friedel pairs is correct. If it is not, please give the correct count in the _publ_section_exptl_refinement section of the submitted CIF.

Comment top

Ionization of 4'-hydroxyacetophenone, (1), as an oxygen acid gives an anion, (2), whose negative charge can be delocalized into its acetyl group (see Scheme). This gives the anion an additional basic site, whose protonation provides the enolic species (3).

Enols are weakly acidic substances with pKa = 10–11 (Keeffe & Kresge, 1990), and pKa = 9 may be estimated for the hydroxyl group of (1) using a σρ relationship that correlates acidity constants of phenols (Perrin et al., 1981). Combination of these two values then gives pK = 9 - (10–11) = -(1–2) for the equilibrium constant relating (1) and (3). This suggests that (3), and not (1), is the structure of 4'-hydroxyacetophenone.

In order to determine whether or not this is so, we carried out the present X-ray diffraction analysis. The results show unequivocally that the correct structure is the phenolic one shown as (1), and not the enolic one shown as (3).

This conclusion is unexpected on the basis of the argument involving pKa's made above. That argument, however, failed to take into account the fact that ionization of (3) converts a cyclohexadiene ring into a ring having some benzenoid character. The ionization therefore benefits from a gain in benzenoid resonance energy, and that makes (3) a substantially stronger acid than the estimate made above.

The crystal structure of (1) was originally determined by Vainshtein et al. (1974), using visually estimated intensities, which were recorded on photographic film. We have redetermined the structure of (1) at low temperature with more accurate data collected using a CCD area detector. In (1), as in the earlier structure, the space group is P212121 and there are two independent molecules in the asymmetric unit, but there is an expected contraction in the volume of the unit cell of about 1%. In our low-temperature structure the eqivalent bond lengths and angles in each independent molecule (A and B) are the same within experimental error. The only minor difference between molecules A and B is the extent of the rotation of the acetyl group about the C1—C7 bond, with respect to the phenyl ring. This is reflected in the torsion angles of 4.8 (3)° for C2A—C1A—C7A—C8A and 9.6 (3)° for C2B—C1B—C7B—C8B.

In (1), pairs of independent molecules (A and B) are are linked through one type of –O—H···OC– hydrogen bond (H···O 1.87 Å) and each hydrogen-bonded pair is linked, in turn, through 21 screw axes to form chains in the a direction via another type of –O—H···OC– hydrogen bond (H···O 1.90 Å) (see Fig. 2 and Table 2). Since there are two distinct O—H···O hydrogen bonds, the primary graph set (N1) is DD and the secondary graph set (N2) is C22(16) (Bernstein et al., 1995).

Experimental top

Please provide some preparation or crystallization information.

Refinement top

All H atoms were included in calculated positions, with distances of 0.95 and 0.98 Å for C—H and of 0.84 Å for O—H. In the refinement, H atoms were included in a riding-motion approximation, with Uiso = 1.2Ueq (1.5Ueq for methyl H atoms) of the carrier atom. Owing to a lack of significant amomalous scatterers, the absolute stereochemistry could not be determined and Friedel pairs were merged before refinement cycles. Succesive attempts to crystallize the sample gave crystals that were brittle needles and were difficult to cut. The best crystal possible that was finally selected for data collection gave diffuse diffraction spots, indicating the crystal had a large mosciac spread. As a result of this, a few of the diffraction spots were overlapping and the integration of these spots could not be carried out properly by the processing software. A small portion of the reflections collected were therefore rejected on the basis that they were measured incorrectly. Despite this, the title structure was refined using 97.6% of the possible data, which is adequate to give a precise structure.

Computing details top

Data collection: COLLECT (Nonius, 1997-2001); cell refinement: DENZO–SMN (Otwinowski & Minor, 1997); data reduction: DENZO–SMN; program(s) used to solve structure: SHELXTL (Sheldrick, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. View of both independent molecules in (1), with displacement ellipsoids drawn at the 50% probability level.
[Figure 2] Fig. 2. View of the hydrogen bonding in (1) [symmetry cod: (i) 3/2 − x, 1 − y, 1/2 + z].
4'-Hydroxyacetophenone top
Crystal data top
C8H8O2F(000) = 576
Mr = 136.14Dx = 1.314 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 1020 reflections
a = 6.1886 (4) Åθ = 2.6–25.0°
b = 9.0710 (6) ŵ = 0.09 mm1
c = 24.5261 (15) ÅT = 150 K
V = 1376.82 (15) Å3Needle, colourless
Z = 80.40 × 0.30 × 0.25 mm
Data collection top
Nonius KappaCCD
diffractometer
1284 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.032
Graphite monochromatorθmax = 25.0°, θmin = 1.7°
Detector resolution: 9 pixels mm-1h = 77
ϕ scans and ω scans with κ offsetsk = 1010
3693 measured reflectionsl = 2929
1405 independent reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.034H-atom parameters constrained
wR(F2) = 0.087 w = 1/[σ2(Fo2) + (0.0428P)2 + 0.1416P]
where P = (Fo2 + 2Fc2)/3
S = 1.08(Δ/σ)max < 0.001
1405 reflectionsΔρmax = 0.09 e Å3
186 parametersΔρmin = 0.11 e Å3
0 restraintsExtinction correction: SHELXTL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.037 (11)
Crystal data top
C8H8O2V = 1376.82 (15) Å3
Mr = 136.14Z = 8
Orthorhombic, P212121Mo Kα radiation
a = 6.1886 (4) ŵ = 0.09 mm1
b = 9.0710 (6) ÅT = 150 K
c = 24.5261 (15) Å0.40 × 0.30 × 0.25 mm
Data collection top
Nonius KappaCCD
diffractometer
1284 reflections with I > 2σ(I)
3693 measured reflectionsRint = 0.032
1405 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0340 restraints
wR(F2) = 0.087H-atom parameters constrained
S = 1.08Δρmax = 0.09 e Å3
1405 reflectionsΔρmin = 0.11 e Å3
186 parameters
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
O1A0.9900 (3)0.7943 (2)0.22764 (6)0.0655 (5)
O2A0.2191 (2)0.85197 (17)0.39604 (6)0.0533 (4)
H2A0.24220.77880.41620.080*
C1A0.6839 (4)0.8823 (2)0.27513 (8)0.0444 (5)
C2A0.5085 (4)0.9759 (2)0.27658 (8)0.0507 (6)
H2AA0.49341.04880.24900.061*
C3A0.3544 (4)0.9664 (2)0.31707 (9)0.0517 (6)
H3AA0.23461.03190.31720.062*
C4A0.3756 (3)0.8604 (2)0.35758 (8)0.0440 (5)
C5A0.5527 (4)0.7675 (3)0.35731 (8)0.0522 (6)
H5AA0.56960.69610.38530.063*
C6A0.7045 (4)0.7785 (3)0.31656 (8)0.0532 (6)
H6AA0.82550.71400.31670.064*
C7A0.8452 (4)0.8859 (2)0.23062 (8)0.0496 (6)
C8A0.8244 (5)1.0039 (3)0.18813 (9)0.0643 (7)
H8AA0.93650.99040.16030.096*
H8AB0.84161.10080.20520.096*
H8AC0.68160.99770.17100.096*
O1B0.2677 (3)0.63134 (18)0.46931 (6)0.0557 (4)
O2B0.1669 (3)0.16396 (19)0.65927 (6)0.0660 (5)
H2B0.27160.18580.67950.099*
C1B0.1267 (3)0.4480 (2)0.52756 (7)0.0413 (5)
C2B0.0365 (4)0.3475 (2)0.53879 (8)0.0468 (5)
H2BA0.16120.34460.51620.056*
C3B0.0199 (4)0.2517 (3)0.58234 (9)0.0522 (6)
H3BA0.13120.18210.58930.063*
C4B0.1614 (4)0.2577 (2)0.61606 (8)0.0494 (6)
C5B0.3267 (4)0.3557 (3)0.60486 (8)0.0490 (5)
H5BA0.45150.35820.62740.059*
C6B0.3099 (4)0.4497 (2)0.56082 (8)0.0469 (5)
H6BA0.42430.51630.55300.056*
C7B0.1108 (4)0.5552 (2)0.48232 (8)0.0446 (5)
C8B0.0998 (4)0.5725 (3)0.45297 (8)0.0530 (6)
H8BA0.08880.65380.42680.079*
H8BB0.21440.59390.47940.079*
H8BC0.13400.48110.43350.079*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O1A0.0579 (11)0.0847 (11)0.0540 (9)0.0079 (10)0.0177 (9)0.0033 (9)
O2A0.0437 (8)0.0628 (9)0.0535 (9)0.0044 (9)0.0148 (7)0.0043 (7)
C1A0.0421 (11)0.0538 (11)0.0373 (10)0.0071 (11)0.0021 (9)0.0077 (9)
C2A0.0564 (14)0.0485 (11)0.0473 (11)0.0020 (11)0.0069 (11)0.0024 (10)
C3A0.0481 (13)0.0491 (11)0.0578 (13)0.0064 (11)0.0089 (11)0.0016 (10)
C4A0.0373 (11)0.0547 (11)0.0401 (11)0.0003 (11)0.0045 (9)0.0047 (9)
C5A0.0441 (12)0.0734 (14)0.0392 (11)0.0099 (12)0.0025 (10)0.0074 (10)
C6A0.0405 (12)0.0760 (14)0.0432 (11)0.0154 (13)0.0047 (10)0.0018 (11)
C7A0.0472 (13)0.0595 (12)0.0422 (11)0.0141 (12)0.0061 (10)0.0124 (10)
C8A0.0680 (17)0.0665 (13)0.0584 (14)0.0158 (15)0.0223 (13)0.0018 (11)
O1B0.0473 (9)0.0695 (9)0.0504 (9)0.0048 (9)0.0017 (7)0.0057 (8)
O2B0.0638 (12)0.0788 (11)0.0555 (10)0.0107 (10)0.0226 (8)0.0184 (9)
C1B0.0388 (11)0.0489 (10)0.0363 (10)0.0028 (10)0.0030 (9)0.0083 (9)
C2B0.0415 (12)0.0556 (12)0.0433 (11)0.0025 (11)0.0099 (9)0.0029 (10)
C3B0.0459 (13)0.0603 (13)0.0504 (12)0.0100 (12)0.0122 (11)0.0049 (10)
C4B0.0518 (13)0.0532 (11)0.0432 (11)0.0010 (12)0.0098 (11)0.0004 (10)
C5B0.0416 (11)0.0616 (12)0.0437 (11)0.0013 (12)0.0108 (10)0.0049 (10)
C6B0.0394 (11)0.0553 (11)0.0459 (11)0.0017 (11)0.0037 (10)0.0059 (10)
C7B0.0443 (12)0.0526 (11)0.0370 (10)0.0049 (12)0.0007 (9)0.0071 (9)
C8B0.0496 (13)0.0655 (13)0.0439 (12)0.0006 (12)0.0049 (10)0.0045 (10)
Geometric parameters (Å, º) top
O1A—C7A1.224 (3)O1B—C7B1.234 (3)
O2A—C4A1.354 (2)O2B—C4B1.359 (3)
O2A—H2A0.840O2B—H2B0.840
C1A—C2A1.379 (3)C1B—C2B1.389 (3)
C1A—C6A1.391 (3)C1B—C6B1.397 (3)
C1A—C7A1.479 (3)C1B—C7B1.478 (3)
C2A—C3A1.380 (3)C2B—C3B1.381 (3)
C2A—H2AA0.950C2B—H2BA0.950
C3A—C4A1.389 (3)C3B—C4B1.395 (3)
C3A—H3AA0.950C3B—H3BA0.950
C4A—C5A1.382 (3)C4B—C5B1.383 (3)
C5A—C6A1.375 (3)C5B—C6B1.380 (3)
C5A—H5AA0.950C5B—H5BA0.950
C6A—H6AA0.950C6B—H6BA0.950
C7A—C8A1.499 (3)C7B—C8B1.497 (3)
C8A—H8AA0.980C8B—H8BA0.980
C8A—H8AB0.980C8B—H8BB0.980
C8A—H8AC0.980C8B—H8BC0.980
C4A—O2A—H2A109.5C4B—O2B—H2B109.5
C2A—C1A—C6A118.05 (19)C2B—C1B—C6B118.78 (19)
C2A—C1A—C7A122.4 (2)C2B—C1B—C7B122.16 (19)
C6A—C1A—C7A119.5 (2)C6B—C1B—C7B119.04 (19)
C1A—C2A—C3A121.6 (2)C3B—C2B—C1B120.84 (19)
C1A—C2A—H2AA119.2C3B—C2B—H2BA119.6
C3A—C2A—H2AA119.2C1B—C2B—H2BA119.6
C2A—C3A—C4A119.5 (2)C2B—C3B—C4B119.6 (2)
C2A—C3A—H3AA120.2C2B—C3B—H3BA120.2
C4A—C3A—H3AA120.2C4B—C3B—H3BA120.2
O2A—C4A—C5A122.43 (19)O2B—C4B—C5B122.6 (2)
O2A—C4A—C3A118.00 (18)O2B—C4B—C3B117.3 (2)
C5A—C4A—C3A119.57 (19)C5B—C4B—C3B120.16 (19)
C6A—C5A—C4A120.1 (2)C6B—C5B—C4B119.8 (2)
C6A—C5A—H5AA120.0C6B—C5B—H5BA120.1
C4A—C5A—H5AA120.0C4B—C5B—H5BA120.1
C5A—C6A—C1A121.1 (2)C5B—C6B—C1B120.8 (2)
C5A—C6A—H6AA119.4C5B—C6B—H6BA119.6
C1A—C6A—H6AA119.4C1B—C6B—H6BA119.6
O1A—C7A—C1A121.5 (2)O1B—C7B—C1B120.64 (19)
O1A—C7A—C8A120.4 (2)O1B—C7B—C8B120.15 (19)
C1A—C7A—C8A118.1 (2)C1B—C7B—C8B119.2 (2)
C7A—C8A—H8AA109.5C7B—C8B—H8BA109.5
C7A—C8A—H8AB109.5C7B—C8B—H8BB109.5
H8AA—C8A—H8AB109.5H8BA—C8B—H8BB109.5
C7A—C8A—H8AC109.5C7B—C8B—H8BC109.5
H8AA—C8A—H8AC109.5H8BA—C8B—H8BC109.5
H8AB—C8A—H8AC109.5H8BB—C8B—H8BC109.5
C6A—C1A—C2A—C3A1.2 (3)C6B—C1B—C2B—C3B0.7 (3)
C7A—C1A—C2A—C3A177.0 (2)C7B—C1B—C2B—C3B178.03 (19)
C1A—C2A—C3A—C4A0.1 (3)C1B—C2B—C3B—C4B1.1 (3)
C2A—C3A—C4A—O2A178.6 (2)C2B—C3B—C4B—O2B178.2 (2)
C2A—C3A—C4A—C5A1.1 (3)C2B—C3B—C4B—C5B2.2 (3)
O2A—C4A—C5A—C6A178.5 (2)O2B—C4B—C5B—C6B179.0 (2)
C3A—C4A—C5A—C6A1.3 (3)C3B—C4B—C5B—C6B1.3 (3)
C4A—C5A—C6A—C1A0.1 (4)C4B—C5B—C6B—C1B0.5 (3)
C2A—C1A—C6A—C5A1.1 (3)C2B—C1B—C6B—C5B1.5 (3)
C7A—C1A—C6A—C5A177.2 (2)C7B—C1B—C6B—C5B177.23 (19)
C2A—C1A—C7A—O1A174.0 (2)C2B—C1B—C7B—O1B171.5 (2)
C6A—C1A—C7A—O1A4.1 (3)C6B—C1B—C7B—O1B9.7 (3)
C2A—C1A—C7A—C8A4.8 (3)C2B—C1B—C7B—C8B9.6 (3)
C6A—C1A—C7A—C8A177.0 (2)C6B—C1B—C7B—C8B169.11 (19)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2A—H2A···O1B0.841.872.707 (2)171
O2B—H2B···O1Ai0.841.902.732 (2)172
Symmetry code: (i) x+3/2, y+1, z+1/2.

Experimental details

Crystal data
Chemical formulaC8H8O2
Mr136.14
Crystal system, space groupOrthorhombic, P212121
Temperature (K)150
a, b, c (Å)6.1886 (4), 9.0710 (6), 24.5261 (15)
V3)1376.82 (15)
Z8
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.40 × 0.30 × 0.25
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
3693, 1405, 1284
Rint0.032
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.034, 0.087, 1.08
No. of reflections1405
No. of parameters186
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.09, 0.11

Computer programs: COLLECT (Nonius, 1997-2001), DENZO–SMN (Otwinowski & Minor, 1997), DENZO–SMN, SHELXTL (Sheldrick, 2001), SHELXTL.

Selected geometric parameters (Å, º) top
O1A—C7A1.224 (3)O1B—C7B1.234 (3)
O2A—C4A1.354 (2)O2B—C4B1.359 (3)
C1A—C7A1.479 (3)C1B—C7B1.478 (3)
C7A—C8A1.499 (3)C7B—C8B1.497 (3)
O1A—C7A—C1A121.5 (2)O1B—C7B—C1B120.64 (19)
O1A—C7A—C8A120.4 (2)O1B—C7B—C8B120.15 (19)
C1A—C7A—C8A118.1 (2)C1B—C7B—C8B119.2 (2)
C2A—C1A—C7A—O1A174.0 (2)C2B—C1B—C7B—O1B171.5 (2)
C2A—C1A—C7A—C8A4.8 (3)C2B—C1B—C7B—C8B9.6 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2A—H2A···O1B0.841.872.707 (2)171
O2B—H2B···O1Ai0.841.902.732 (2)172
Symmetry code: (i) x+3/2, y+1, z+1/2.
 

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