The orthorhombic form of 2-hydroxycyclopent-2-enone, C5H6O2, consists of chains of hydrogen-bonded molecules aligned along a twofold screw axis. The monoclinic form contains two independent molecules, which have different orientations of the hydroxyl proton, and which assemble into ribbons along a twofold screw axis.
Supporting information
CCDC references: 152622; 152623
The title compound was prepared by a literature procedure (Acheson, 1956). Crystals of the orthorhombic form of (2) were obtained by low-temperature crystallization (195 K) from a mixture (5:1) of n-hexane and ethyl acetate. Vacuum distillation (351–359 K, 8 m mH g) of (II) furnished crystals of the monoclinic form.
Crystal decay was monitored by the measurement of duplicate reflections. The tautomeric hydroxyl hydrogen atoms were located by difference Fourier calculations and their positions refined. CH H atoms were placed in calculated positions. The absolute configuration of the orthorhombic form could not be determined, as judged by the Flack parameter [−0.4 (18)](Flack, 1983).
For both compounds, data collection: SMART (Siemens 1999); cell refinement: SAINT (Siemens 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXL97; software used to prepare material for publication: SHELXL97.
(3sm1) 3-Hydroxycyclopent-2-enone
top
Crystal data top
C5H6O2 | Dx = 1.363 Mg m−3 |
Mr = 98.10 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, P212121 | Cell parameters from 1694 reflections |
a = 5.370 (5) Å | θ = 3.1–25.0° |
b = 8.971 (8) Å | µ = 0.11 mm−1 |
c = 9.920 (9) Å | T = 163 K |
V = 477.9 (8) Å3 | Plate, colourless |
Z = 4 | 0.68 × 0.18 × 0.01 mm |
F(000) = 208 | |
Data collection top
Siemens SMART CCD diffractometer | 835 independent reflections |
Radiation source: fine-focus sealed tube | 674 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.033 |
Detector resolution: 8.19 pixels mm-1 | θmax = 25.0°, θmin = 3.1° |
Exposures over 0.5° ϕ or ω rotation scans | h = −6→3 |
Absorption correction: multi-scan (SADABS; Siemens, 1999) | k = −10→10 |
Tmin = 0.806, Tmax = 0.968 | l = −11→11 |
5395 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)] = 0.032 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.070 | w = 1/[σ2(Fo2) + (0.0411P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.98 | (Δ/σ)max = 0.001 |
835 reflections | Δρmax = 0.12 e Å−3 |
67 parameters | Δρmin = −0.16 e Å−3 |
0 restraints | Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881 |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: −0.4 (18) |
Crystal data top
C5H6O2 | V = 477.9 (8) Å3 |
Mr = 98.10 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 5.370 (5) Å | µ = 0.11 mm−1 |
b = 8.971 (8) Å | T = 163 K |
c = 9.920 (9) Å | 0.68 × 0.18 × 0.01 mm |
Data collection top
Siemens SMART CCD diffractometer | 835 independent reflections |
Absorption correction: multi-scan (SADABS; Siemens, 1999) | 674 reflections with I > 2σ(I) |
Tmin = 0.806, Tmax = 0.968 | Rint = 0.033 |
5395 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.032 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.070 | Δρmax = 0.12 e Å−3 |
S = 0.98 | Δρmin = −0.16 e Å−3 |
835 reflections | Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881 |
67 parameters | Absolute structure parameter: −0.4 (18) |
0 restraints | |
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 | x | y | z | Uiso*/Ueq | |
O1 | 0.4244 (2) | 0.81562 (13) | 0.55387 (12) | 0.0402 (4) | |
C1 | 0.4856 (3) | 0.92964 (18) | 0.49219 (18) | 0.0328 (5) | |
O2 | 0.1665 (2) | 0.90991 (14) | 0.31264 (12) | 0.0390 (4) | |
H2 | 0.127 (4) | 0.834 (2) | 0.362 (2) | 0.047* | |
C2 | 0.3634 (3) | 0.98241 (19) | 0.36880 (18) | 0.0305 (4) | |
C3 | 0.4726 (3) | 1.10732 (19) | 0.32288 (19) | 0.0347 (5) | |
H3 | 0.4191 | 1.1607 | 0.2454 | 0.042* | |
C4 | 0.6891 (4) | 1.15175 (19) | 0.40908 (18) | 0.0376 (5) | |
H4A | 0.6671 | 1.2542 | 0.4442 | 0.045* | |
H4B | 0.8465 | 1.1471 | 0.3573 | 0.045* | |
C5 | 0.6902 (4) | 1.03691 (18) | 0.52556 (18) | 0.0369 (5) | |
H5A | 0.8526 | 0.9849 | 0.5305 | 0.044* | |
H5B | 0.6580 | 1.0865 | 0.6130 | 0.044* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0421 (9) | 0.0328 (7) | 0.0457 (8) | 0.0019 (6) | 0.0011 (6) | 0.0106 (6) |
C1 | 0.0331 (12) | 0.0292 (9) | 0.0362 (10) | 0.0074 (8) | 0.0038 (9) | −0.0027 (9) |
O2 | 0.0459 (9) | 0.0319 (7) | 0.0392 (7) | −0.0053 (7) | −0.0047 (7) | 0.0056 (6) |
C2 | 0.0322 (11) | 0.0274 (9) | 0.0317 (9) | 0.0046 (8) | 0.0013 (8) | −0.0043 (8) |
C3 | 0.0402 (12) | 0.0291 (10) | 0.0348 (10) | 0.0024 (9) | 0.0034 (9) | 0.0023 (8) |
C4 | 0.0426 (13) | 0.0278 (9) | 0.0423 (11) | 0.0000 (10) | 0.0023 (9) | 0.0027 (7) |
C5 | 0.0377 (12) | 0.0339 (9) | 0.0390 (11) | 0.0009 (9) | 0.0006 (10) | 0.0000 (8) |
Geometric parameters (Å, º) top
O1—C1 | 1.236 (2) | C3—H3 | 0.9500 |
C1—C2 | 1.467 (3) | C4—C5 | 1.548 (3) |
C1—C5 | 1.498 (3) | C4—H4A | 0.9900 |
O2—C2 | 1.361 (2) | C4—H4B | 0.9900 |
O2—H2 | 0.87 (2) | C5—H5A | 0.9900 |
C2—C3 | 1.344 (3) | C5—H5B | 0.9900 |
C3—C4 | 1.497 (3) | | |
| | | |
O1—C1—C2 | 124.13 (17) | C3—C4—H4A | 110.8 |
O1—C1—C5 | 128.10 (17) | C5—C4—H4A | 110.8 |
C2—C1—C5 | 107.77 (15) | C3—C4—H4B | 110.8 |
C2—O2—H2 | 109.6 (13) | C5—C4—H4B | 110.8 |
C3—C2—O2 | 126.77 (19) | H4A—C4—H4B | 108.9 |
C3—C2—C1 | 110.90 (18) | C1—C5—C4 | 105.05 (15) |
O2—C2—C1 | 122.33 (16) | C1—C5—H5A | 110.7 |
C2—C3—C4 | 111.53 (17) | C4—C5—H5A | 110.7 |
C2—C3—H3 | 124.2 | C1—C5—H5B | 110.7 |
C4—C3—H3 | 124.2 | C4—C5—H5B | 110.7 |
C3—C4—C5 | 104.61 (15) | H5A—C5—H5B | 108.8 |
| | | |
O1—C1—C2—C3 | −178.77 (17) | C1—C2—C3—C4 | 1.6 (2) |
C5—C1—C2—C3 | 0.93 (19) | C2—C3—C4—C5 | −3.40 (19) |
O1—C1—C2—O2 | 1.2 (3) | O1—C1—C5—C4 | 176.75 (17) |
C5—C1—C2—O2 | −179.14 (15) | C2—C1—C5—C4 | −2.93 (18) |
O2—C2—C3—C4 | −178.30 (15) | C3—C4—C5—C1 | 3.72 (18) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O1i | 0.87 (2) | 1.92 (2) | 2.745 (2) | 159.5 (18) |
Symmetry code: (i) x−1/2, −y+3/2, −z+1. |
(3sm2) 3-Hydroxycyclopent-2-enone
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Crystal data top
C5H6O2 | F(000) = 416 |
Mr = 98.10 | Dx = 1.371 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 9.100 (7) Å | Cell parameters from 1577 reflections |
b = 10.761 (8) Å | θ = 2.7–25.0° |
c = 10.124 (7) Å | µ = 0.11 mm−1 |
β = 106.491 (11)° | T = 163 K |
V = 950.6 (12) Å3 | Plate, colourless |
Z = 8 | 0.45 × 0.18 × 0.03 mm |
Data collection top
Siemens SMART CCD diffractometer | 1669 independent reflections |
Radiation source: fine-focus sealed tube | 973 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.059 |
Detector resolution: 8.19 pixels mm-1 | θmax = 25.0°, θmin = 2.7° |
Exposures over 0.5° ϕ or ω rotation scans | h = −10→10 |
Absorption correction: multi-scan (SADABS; Siemens, 1999) | k = −8→12 |
Tmin = 0.838, Tmax = 0.968 | l = −12→12 |
10377 measured reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.043 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.115 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.91 | w = 1/[σ2(Fo2) + (0.0639P)2] where P = (Fo2 + 2Fc2)/3 |
1669 reflections | (Δ/σ)max = 0.001 |
133 parameters | Δρmax = 0.20 e Å−3 |
0 restraints | Δρmin = −0.23 e Å−3 |
Crystal data top
C5H6O2 | V = 950.6 (12) Å3 |
Mr = 98.10 | Z = 8 |
Monoclinic, P21/n | Mo Kα radiation |
a = 9.100 (7) Å | µ = 0.11 mm−1 |
b = 10.761 (8) Å | T = 163 K |
c = 10.124 (7) Å | 0.45 × 0.18 × 0.03 mm |
β = 106.491 (11)° | |
Data collection top
Siemens SMART CCD diffractometer | 1669 independent reflections |
Absorption correction: multi-scan (SADABS; Siemens, 1999) | 973 reflections with I > 2σ(I) |
Tmin = 0.838, Tmax = 0.968 | Rint = 0.059 |
10377 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.043 | 0 restraints |
wR(F2) = 0.115 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.91 | Δρmax = 0.20 e Å−3 |
1669 reflections | Δρmin = −0.23 e Å−3 |
133 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 | x | y | z | Uiso*/Ueq | |
O1 | −0.01294 (19) | 0.97162 (14) | 0.31624 (18) | 0.0394 (5) | |
C1 | −0.0384 (3) | 0.8592 (2) | 0.3039 (2) | 0.0279 (6) | |
O2 | −0.30962 (19) | 0.88026 (14) | 0.18963 (17) | 0.0324 (5) | |
H2 | −0.400 (3) | 0.841 (2) | 0.165 (2) | 0.039* | |
C2 | −0.1883 (3) | 0.8033 (2) | 0.2408 (2) | 0.0248 (6) | |
C3 | −0.1780 (3) | 0.6789 (2) | 0.2446 (2) | 0.0288 (6) | |
H3A | −0.2620 | 0.6244 | 0.2087 | 0.035* | |
C4 | −0.0173 (3) | 0.6368 (2) | 0.3125 (3) | 0.0314 (6) | |
H4A | 0.0215 | 0.5851 | 0.2487 | 0.038* | |
H4B | −0.0127 | 0.5876 | 0.3962 | 0.038* | |
C5 | 0.0774 (3) | 0.7567 (2) | 0.3499 (2) | 0.0299 (6) | |
H5A | 0.1273 | 0.7613 | 0.4503 | 0.036* | |
H5B | 0.1571 | 0.7612 | 0.3009 | 0.036* | |
O1' | 0.07451 (18) | 1.24911 (14) | 0.38355 (16) | 0.0346 (5) | |
C1' | 0.2140 (3) | 1.2611 (2) | 0.4336 (2) | 0.0243 (5) | |
O2' | 0.2776 (2) | 1.03840 (14) | 0.44591 (19) | 0.0411 (5) | |
H2' | 0.173 (3) | 1.029 (2) | 0.399 (3) | 0.049* | |
C2' | 0.3226 (3) | 1.1582 (2) | 0.4693 (2) | 0.0285 (6) | |
C3' | 0.4651 (3) | 1.1992 (2) | 0.5248 (2) | 0.0315 (6) | |
H3'A | 0.5520 | 1.1466 | 0.5551 | 0.038* | |
C4' | 0.4717 (3) | 1.3385 (2) | 0.5337 (3) | 0.0320 (6) | |
H4'A | 0.5408 | 1.3725 | 0.4828 | 0.038* | |
H4'B | 0.5077 | 1.3663 | 0.6308 | 0.038* | |
C5' | 0.3046 (3) | 1.3794 (2) | 0.4666 (2) | 0.0288 (6) | |
H5'A | 0.2669 | 1.4311 | 0.5311 | 0.035* | |
H5'B | 0.2966 | 1.4278 | 0.3817 | 0.035* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0394 (11) | 0.0174 (11) | 0.0576 (12) | −0.0065 (8) | 0.0076 (9) | 0.0000 (8) |
C1 | 0.0339 (16) | 0.0253 (15) | 0.0252 (14) | −0.0021 (11) | 0.0098 (12) | 0.0017 (10) |
O2 | 0.0289 (10) | 0.0195 (10) | 0.0452 (11) | −0.0017 (8) | 0.0046 (9) | 0.0020 (8) |
C2 | 0.0273 (14) | 0.0214 (14) | 0.0253 (14) | 0.0002 (11) | 0.0069 (11) | 0.0023 (10) |
C3 | 0.0335 (15) | 0.0214 (15) | 0.0310 (14) | −0.0059 (11) | 0.0083 (12) | −0.0003 (11) |
C4 | 0.0394 (16) | 0.0183 (14) | 0.0382 (15) | 0.0007 (11) | 0.0138 (13) | 0.0034 (11) |
C5 | 0.0289 (14) | 0.0270 (14) | 0.0332 (13) | −0.0005 (11) | 0.0081 (11) | 0.0041 (11) |
O1' | 0.0318 (11) | 0.0238 (10) | 0.0459 (11) | 0.0041 (8) | 0.0072 (8) | −0.0027 (8) |
C1' | 0.0260 (14) | 0.0218 (14) | 0.0255 (13) | 0.0007 (11) | 0.0078 (11) | 0.0000 (11) |
O2' | 0.0313 (11) | 0.0136 (10) | 0.0726 (14) | −0.0014 (8) | 0.0050 (10) | −0.0044 (8) |
C2' | 0.0304 (15) | 0.0195 (14) | 0.0346 (15) | 0.0000 (11) | 0.0078 (12) | −0.0017 (10) |
C3' | 0.0321 (16) | 0.0230 (14) | 0.0395 (16) | 0.0026 (11) | 0.0100 (12) | −0.0012 (11) |
C4' | 0.0386 (16) | 0.0223 (14) | 0.0369 (15) | −0.0070 (11) | 0.0135 (13) | −0.0038 (11) |
C5' | 0.0368 (15) | 0.0179 (13) | 0.0346 (15) | −0.0019 (11) | 0.0146 (12) | −0.0024 (10) |
Geometric parameters (Å, º) top
O1—C1 | 1.231 (3) | O1'—C1' | 1.232 (3) |
C1—C2 | 1.461 (3) | C1'—C2' | 1.460 (3) |
C1—C5 | 1.505 (3) | C1'—C5' | 1.502 (3) |
O2—C2 | 1.360 (3) | O2'—C2' | 1.353 (3) |
O2—H2 | 0.89 (2) | O2'—H2' | 0.94 (3) |
C2—C3 | 1.341 (3) | C2'—C3' | 1.333 (3) |
C3—C4 | 1.499 (3) | C3'—C4' | 1.502 (3) |
C3—H3A | 0.9500 | C3'—H3'A | 0.9500 |
C4—C5 | 1.538 (3) | C4'—C5' | 1.543 (3) |
C4—H4A | 0.9900 | C4'—H4'A | 0.9900 |
C4—H4B | 0.9900 | C4'—H4'B | 0.9900 |
C5—H5A | 0.9900 | C5'—H5'A | 0.9900 |
C5—H5B | 0.9900 | C5'—H5'B | 0.9900 |
| | | |
O1—C1—C2 | 125.1 (2) | O1'—C1'—C2' | 124.6 (2) |
O1—C1—C5 | 126.4 (2) | O1'—C1'—C5' | 128.1 (2) |
C2—C1—C5 | 108.5 (2) | C2'—C1'—C5' | 107.3 (2) |
C2—O2—H2 | 113.9 (15) | C2'—O2'—H2' | 113.5 (15) |
C3—C2—O2 | 131.4 (2) | C3'—C2'—O2' | 126.8 (2) |
C3—C2—C1 | 110.5 (2) | C3'—C2'—C1' | 111.3 (2) |
O2—C2—C1 | 118.1 (2) | O2'—C2'—C1' | 121.9 (2) |
C2—C3—C4 | 111.5 (2) | C2'—C3'—C4' | 111.9 (2) |
C2—C3—H3A | 124.3 | C2'—C3'—H3'A | 124.0 |
C4—C3—H3A | 124.3 | C4'—C3'—H3'A | 124.0 |
C3—C4—C5 | 105.34 (18) | C3'—C4'—C5' | 103.92 (18) |
C3—C4—H4A | 110.7 | C3'—C4'—H4'A | 111.0 |
C5—C4—H4A | 110.7 | C5'—C4'—H4'A | 111.0 |
C3—C4—H4B | 110.7 | C3'—C4'—H4'B | 111.0 |
C5—C4—H4B | 110.7 | C5'—C4'—H4'B | 111.0 |
H4A—C4—H4B | 108.8 | H4'A—C4'—H4'B | 109.0 |
C1—C5—C4 | 104.17 (19) | C1'—C5'—C4' | 105.47 (18) |
C1—C5—H5A | 110.9 | C1'—C5'—H5'A | 110.6 |
C4—C5—H5A | 110.9 | C4'—C5'—H5'A | 110.6 |
C1—C5—H5B | 110.9 | C1'—C5'—H5'B | 110.6 |
C4—C5—H5B | 110.9 | C4'—C5'—H5'B | 110.6 |
H5A—C5—H5B | 108.9 | H5'A—C5'—H5'B | 108.8 |
| | | |
O1—C1—C2—C3 | −179.4 (2) | O1'—C1'—C2'—C3' | −178.4 (2) |
C5—C1—C2—C3 | 0.8 (3) | C5'—C1'—C2'—C3' | 2.7 (3) |
O1—C1—C2—O2 | 1.0 (3) | O1'—C1'—C2'—O2' | 1.9 (4) |
C5—C1—C2—O2 | −178.84 (19) | C5'—C1'—C2'—O2' | −177.0 (2) |
O2—C2—C3—C4 | 179.9 (2) | O2'—C2'—C3'—C4' | 179.5 (2) |
C1—C2—C3—C4 | 0.3 (3) | C1'—C2'—C3'—C4' | −0.2 (3) |
C2—C3—C4—C5 | −1.3 (3) | C2'—C3'—C4'—C5' | −2.4 (3) |
O1—C1—C5—C4 | 178.7 (2) | O1'—C1'—C5'—C4' | 177.2 (2) |
C2—C1—C5—C4 | −1.5 (2) | C2'—C1'—C5'—C4' | −4.0 (2) |
C3—C4—C5—C1 | 1.6 (2) | C3'—C4'—C5'—C1' | 3.8 (2) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O2′—H2′···O1 | 0.94 (3) | 1.77 (3) | 2.694 (3) | 165 (2) |
O2—H2···O1′i | 0.89 (2) | 1.82 (2) | 2.709 (3) | 175 (2) |
Symmetry code: (i) −x−1/2, y−1/2, −z+1/2. |
Experimental details
| (3sm1) | (3sm2) |
Crystal data |
Chemical formula | C5H6O2 | C5H6O2 |
Mr | 98.10 | 98.10 |
Crystal system, space group | Orthorhombic, P212121 | Monoclinic, P21/n |
Temperature (K) | 163 | 163 |
a, b, c (Å) | 5.370 (5), 8.971 (8), 9.920 (9) | 9.100 (7), 10.761 (8), 10.124 (7) |
α, β, γ (°) | 90, 90, 90 | 90, 106.491 (11), 90 |
V (Å3) | 477.9 (8) | 950.6 (12) |
Z | 4 | 8 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.11 | 0.11 |
Crystal size (mm) | 0.68 × 0.18 × 0.01 | 0.45 × 0.18 × 0.03 |
|
Data collection |
Diffractometer | Siemens SMART CCD diffractometer | Siemens SMART CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Siemens, 1999) | Multi-scan (SADABS; Siemens, 1999) |
Tmin, Tmax | 0.806, 0.968 | 0.838, 0.968 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5395, 835, 674 | 10377, 1669, 973 |
Rint | 0.033 | 0.059 |
(sin θ/λ)max (Å−1) | 0.594 | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.032, 0.070, 0.98 | 0.043, 0.115, 0.91 |
No. of reflections | 835 | 1669 |
No. of parameters | 67 | 133 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.12, −0.16 | 0.20, −0.23 |
Absolute structure | Flack H D (1983), Acta Cryst. A39, 876-881 | ? |
Absolute structure parameter | −0.4 (18) | ? |
Selected geometric parameters (Å, º) for (3sm1) topO1—C1 | 1.236 (2) | O2—H2 | 0.87 (2) |
C1—C2 | 1.467 (3) | C2—C3 | 1.344 (3) |
C1—C5 | 1.498 (3) | C3—C4 | 1.497 (3) |
O2—C2 | 1.361 (2) | C4—C5 | 1.548 (3) |
| | | |
O1—C1—C2 | 124.13 (17) | C3—C2—C1 | 110.90 (18) |
O1—C1—C5 | 128.10 (17) | O2—C2—C1 | 122.33 (16) |
C2—C1—C5 | 107.77 (15) | C2—C3—C4 | 111.53 (17) |
C2—O2—H2 | 109.6 (13) | C3—C4—C5 | 104.61 (15) |
C3—C2—O2 | 126.77 (19) | C1—C5—C4 | 105.05 (15) |
Hydrogen-bond geometry (Å, º) for (3sm1) top
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H2···O1i | 0.87 (2) | 1.92 (2) | 2.745 (2) | 159.5 (18) |
Symmetry code: (i) x−1/2, −y+3/2, −z+1. |
Selected geometric parameters (Å, º) for (3sm2) topO1—C1 | 1.231 (3) | O1'—C1' | 1.232 (3) |
C1—C2 | 1.461 (3) | C1'—C2' | 1.460 (3) |
C1—C5 | 1.505 (3) | C1'—C5' | 1.502 (3) |
O2—C2 | 1.360 (3) | O2'—C2' | 1.353 (3) |
O2—H2 | 0.89 (2) | O2'—H2' | 0.94 (3) |
C2—C3 | 1.341 (3) | C2'—C3' | 1.333 (3) |
C3—C4 | 1.499 (3) | C3'—C4' | 1.502 (3) |
C4—C5 | 1.538 (3) | C4'—C5' | 1.543 (3) |
| | | |
O1—C1—C2 | 125.1 (2) | O1'—C1'—C2' | 124.6 (2) |
O1—C1—C5 | 126.4 (2) | O1'—C1'—C5' | 128.1 (2) |
C2—C1—C5 | 108.5 (2) | C2'—C1'—C5' | 107.3 (2) |
C2—O2—H2 | 113.9 (15) | C2'—O2'—H2' | 113.5 (15) |
C3—C2—O2 | 131.4 (2) | C3'—C2'—O2' | 126.8 (2) |
C3—C2—C1 | 110.5 (2) | C3'—C2'—C1' | 111.3 (2) |
O2—C2—C1 | 118.1 (2) | O2'—C2'—C1' | 121.9 (2) |
C2—C3—C4 | 111.5 (2) | C2'—C3'—C4' | 111.9 (2) |
C3—C4—C5 | 105.34 (18) | C3'—C4'—C5' | 103.92 (18) |
C1—C5—C4 | 104.17 (19) | C1'—C5'—C4' | 105.47 (18) |
Hydrogen-bond geometry (Å, º) for (3sm2) top
D—H···A | D—H | H···A | D···A | D—H···A |
O2'—H2'···O1 | 0.94 (3) | 1.77 (3) | 2.694 (3) | 165 (2) |
O2—H2···O1'i | 0.89 (2) | 1.82 (2) | 2.709 (3) | 175 (2) |
Symmetry code: (i) −x−1/2, y−1/2, −z+1/2. |
As part of a study of the Maillard chemistry of dehydroascorbic acid and its decomposition products (Fayle et al., 2000), we have reported the ability of the food-additive cyclotene (I) to act as a cross-linking reagent for model proteins (Fayle et al., 1999). Recently (Fayle et al., 1998), we reported the X-ray crystal structure of the crystalline hydrate of cyclotene, which exists as the hydroxyenone tautomer, (Ib). In a similar context, we are presently investigating the chemistry of the parent diketone (II), which NMR solution studies clearly show exists as the enol tautomer, (IIb). However, this compound displays chemistry that can be attributed to both the diketo tautomer, (IIa), and the enol tautomer, (IIb). During the course of this work, we managed to isolate two crystalline modifications of (II), which raised the intriguing possibility that these might be different stable tautomers of the same compound [a rare phenomenom sometimes called desmotropy (Guard & Steel, 1994; Desiraju, 1983)]. We now report the structures of these two crystalline forms. \sch
The molecular structure in the orthorhombic form is shown in Fig. 1. The successful location and refinement of the potentially tautomeric hydroxyl H atom, along with the bonding geometry (Table 1), unambiguously establish that, in this form, the title compound exists as the hydroxyenone tautomer, (IIb). The cyclopentenone ring is essentially planar [maximum deviation from the mean plane = 0.022 (2) Å for C4]. The bonding geometry is very similar to that in cyclotene, (Ib) (Fayle et al., 1998) and other crystallographically characterized cyclopentenones (Ley et al., 1993; Tsuboi et al., 1983). As shown in Fig. 2, the molecules connect into chains by means of intermolecular hydrogen bonds (Table 2).
The molecule in the monoclinic form exists as the same tautomer (IIb) and has two independent molecules in the asymmetric unit (Fig. 3), which differ in the orientation of the hydroxyl H atom. One molecule has the OH group in a s-cis conformation, as in the orthorhombic form, while the other molecule has an S-trans conformation of the OH group, as was found for cyclotene, (Ib) (Fayle et al., 1998). Apart from this difference, the two independent molecules have very similar geometries to one another (Table 3) and to the orthorhombic form. The two unique molecules are connected by a linear hydrogen bond (Table 4). These pairs of molecules further assemble into a puckered ribbon array (Fig. 4) by means of additional hydrogen bonds.