Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803006536/lh6052sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536803006536/lh6052Ibsup2.hkl |
CCDC reference: 209995
Key indicators
- Single-crystal X-ray study
- T = 173 K
- Mean (C-C) = 0.002 Å
- R factor = 0.038
- wR factor = 0.113
- Data-to-parameter ratio = 23.8
checkCIF results
No syntax errors found ADDSYM reports no extra symmetry
(Z)-α-Chloromethyl-3,3',4,4'-tetramethoxystilbene, (Ib), was prepared according to Li et al. (1997).
H atoms were refined isotropically (?) and were constrained to the ideal geometry using an appropriate riding model. For methyl groups, the C—H distances (0.98 Å) and C—C—H angles (109.5°) were kept fixed, while the torsion angles were allowed to refine with the starting position based on the threefold averaged circular Fourier synthesis.
Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Siemens, 1995); data reduction: SAINT and SADABS (Sheldrick, 2002); program(s) used to solve structure: SHELXTL (Bruker, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2000); software used to prepare material for publication: SHELXTL.
C19H21ClO4 | Z = 2 |
Mr = 348.81 | F(000) = 368 |
Triclinic, P1 | Dx = 1.318 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 9.2561 (1) Å | Cell parameters from 5499 reflections |
b = 10.0669 (2) Å | θ = 2.4–31.5° |
c = 11.5351 (2) Å | µ = 0.24 mm−1 |
α = 104.620 (1)° | T = 173 K |
β = 108.441 (1)° | Prism, colourless |
γ = 109.692 (1)° | 0.52 × 0.40 × 0.18 mm |
V = 879.06 (3) Å3 |
Siemens SMART CCD area-detector diffractometer | 5768 independent reflections |
Radiation source: fine-focus sealed tube | 4859 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.022 |
ω scans | θmax = 31.5°, θmin = 2.4° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2002) | h = −13→13 |
Tmin = 0.887, Tmax = 0.959 | k = −14→14 |
14932 measured reflections | l = −16→16 |
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)] = 0.038 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.113 | H-atom parameters constrained |
S = 1.02 | w = 1/[σ2(Fo2) + (0.0623P)2 + 0.1791P] where P = (Fo2 + 2Fc2)/3 |
5768 reflections | (Δ/σ)max = 0.001 |
242 parameters | Δρmax = 0.43 e Å−3 |
0 restraints | Δρmin = −0.38 e Å−3 |
C19H21ClO4 | γ = 109.692 (1)° |
Mr = 348.81 | V = 879.06 (3) Å3 |
Triclinic, P1 | Z = 2 |
a = 9.2561 (1) Å | Mo Kα radiation |
b = 10.0669 (2) Å | µ = 0.24 mm−1 |
c = 11.5351 (2) Å | T = 173 K |
α = 104.620 (1)° | 0.52 × 0.40 × 0.18 mm |
β = 108.441 (1)° |
Siemens SMART CCD area-detector diffractometer | 5768 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2002) | 4859 reflections with I > 2σ(I) |
Tmin = 0.887, Tmax = 0.959 | Rint = 0.022 |
14932 measured reflections |
R[F2 > 2σ(F2)] = 0.038 | 0 restraints |
wR(F2) = 0.113 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.43 e Å−3 |
5768 reflections | Δρmin = −0.38 e Å−3 |
242 parameters |
Experimental. Data were collected at low temperature using a Siemens SMART CCD diffractometer equiped with a LT-2 device. A full sphere of reciprocal space was scanned by 0.3° steps in ω with a crystal–to–detector distance of 3.97 cm, 15 s per frame. Preliminary orientation matrix was obtained from the first 100 frames using SMART (Siemens, 1995). The collected frames were integrated using the preliminary orientation matrix which was updated every 100 frames. Final cell parameters were obtained by refinement on the position of 5499 reflections with I>10σ(I) after integration of all the frames data using SAINT (Siemens, 1995). |
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 | ||
Cl1 | 0.92631 (4) | 0.58547 (3) | 0.29928 (3) | 0.03820 (9) | |
O1 | 0.38829 (10) | 0.13893 (9) | −0.07825 (7) | 0.02986 (16) | |
O2 | 0.25151 (10) | 0.05992 (9) | −0.33347 (7) | 0.03185 (17) | |
O3 | 1.14109 (11) | 1.24560 (9) | 0.28478 (9) | 0.03629 (19) | |
O4 | 1.46113 (10) | 1.31097 (9) | 0.38519 (9) | 0.03753 (19) | |
C1 | 0.66936 (13) | 0.49354 (11) | −0.09105 (10) | 0.02477 (18) | |
C2 | 0.60024 (12) | 0.39023 (11) | −0.03790 (9) | 0.02422 (18) | |
H2 | 0.6498 | 0.4187 | 0.0558 | 0.031 (3)* | |
C3 | 0.46082 (12) | 0.24764 (11) | −0.12089 (9) | 0.02293 (17) | |
C4 | 0.38404 (12) | 0.20478 (11) | −0.26015 (9) | 0.02408 (18) | |
C5 | 0.44691 (13) | 0.30871 (12) | −0.31246 (10) | 0.02774 (19) | |
H5 | 0.3937 | 0.2821 | −0.4057 | 0.042 (4)* | |
C6 | 0.58815 (13) | 0.45226 (12) | −0.22848 (10) | 0.02774 (19) | |
H6 | 0.6295 | 0.5227 | −0.2653 | 0.039 (4)* | |
C7 | 0.82139 (13) | 0.64411 (11) | −0.00837 (10) | 0.02652 (19) | |
H7 | 0.8220 | 0.7234 | −0.0390 | 0.031 (3)* | |
C8 | 0.96001 (13) | 0.68578 (11) | 0.10461 (10) | 0.02549 (18) | |
C9 | 0.47107 (17) | 0.17140 (14) | 0.06002 (11) | 0.0368 (2) | |
H9A | 0.5899 | 0.1904 | 0.0848 | 0.052 (5)* | |
H9B | 0.4115 | 0.0833 | 0.0773 | 0.050 (4)* | |
H9C | 0.4687 | 0.2629 | 0.1130 | 0.038 (4)* | |
C10 | 0.1916 (2) | 0.00466 (16) | −0.47466 (12) | 0.0501 (4) | |
H10A | 0.1447 | 0.0688 | −0.5079 | 0.066 (6)* | |
H10B | 0.1022 | −0.1022 | −0.5165 | 0.072 (6)* | |
H10C | 0.2867 | 0.0094 | −0.4967 | 0.055 (5)* | |
C11 | 1.09651 (12) | 0.84807 (11) | 0.17693 (10) | 0.02483 (18) | |
C12 | 1.05068 (12) | 0.96931 (11) | 0.19178 (10) | 0.02496 (18) | |
H12 | 0.9334 | 0.9465 | 0.1541 | 0.027 (3)* | |
C13 | 1.17530 (13) | 1.12196 (11) | 0.26097 (10) | 0.02643 (19) | |
C14 | 1.34966 (13) | 1.15711 (12) | 0.31643 (10) | 0.0282 (2) | |
C15 | 1.39521 (13) | 1.03838 (13) | 0.30004 (11) | 0.0308 (2) | |
H15 | 1.5126 | 1.0614 | 0.3354 | 0.048 (4)* | |
C16 | 1.26938 (13) | 0.88464 (12) | 0.23169 (11) | 0.0298 (2) | |
H16 | 1.3023 | 0.8043 | 0.2226 | 0.034 (4)* | |
C17 | 0.96556 (17) | 1.21325 (14) | 0.22613 (16) | 0.0440 (3) | |
H17A | 0.9188 | 1.1659 | 0.1287 | 0.058 (5)* | |
H17B | 0.9563 | 1.3094 | 0.2528 | 0.065 (5)* | |
H17C | 0.9012 | 1.1424 | 0.2566 | 0.046 (4)* | |
C18 | 1.63877 (16) | 1.35314 (16) | 0.44955 (14) | 0.0472 (3) | |
H18A | 1.6577 | 1.3022 | 0.5110 | 0.048 (4)* | |
H18B | 1.7033 | 1.4651 | 0.4996 | 0.075 (6)* | |
H18C | 1.6774 | 1.3210 | 0.3823 | 0.062 (5)* | |
C19 | 0.98628 (14) | 0.57325 (12) | 0.16213 (11) | 0.0295 (2) | |
H19A | 1.1079 | 0.5950 | 0.1949 | 0.043 (4)* | |
H19B | 0.9164 | 0.4675 | 0.0916 | 0.036 (4)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl1 | 0.05197 (18) | 0.02781 (13) | 0.03007 (14) | 0.01506 (12) | 0.01622 (12) | 0.01111 (10) |
O1 | 0.0320 (4) | 0.0281 (3) | 0.0241 (3) | 0.0063 (3) | 0.0128 (3) | 0.0120 (3) |
O2 | 0.0305 (4) | 0.0270 (4) | 0.0221 (3) | 0.0016 (3) | 0.0087 (3) | 0.0056 (3) |
O3 | 0.0330 (4) | 0.0193 (3) | 0.0481 (5) | 0.0079 (3) | 0.0128 (4) | 0.0130 (3) |
O4 | 0.0278 (4) | 0.0269 (4) | 0.0378 (4) | −0.0009 (3) | 0.0055 (3) | 0.0131 (3) |
C1 | 0.0254 (4) | 0.0208 (4) | 0.0267 (4) | 0.0096 (3) | 0.0121 (4) | 0.0077 (3) |
C2 | 0.0251 (4) | 0.0231 (4) | 0.0215 (4) | 0.0091 (3) | 0.0107 (3) | 0.0064 (3) |
C3 | 0.0238 (4) | 0.0226 (4) | 0.0230 (4) | 0.0096 (3) | 0.0122 (3) | 0.0089 (3) |
C4 | 0.0229 (4) | 0.0229 (4) | 0.0227 (4) | 0.0081 (3) | 0.0096 (3) | 0.0074 (3) |
C5 | 0.0278 (4) | 0.0295 (5) | 0.0236 (4) | 0.0107 (4) | 0.0101 (4) | 0.0118 (4) |
C6 | 0.0290 (5) | 0.0256 (4) | 0.0288 (5) | 0.0110 (4) | 0.0126 (4) | 0.0135 (4) |
C7 | 0.0279 (4) | 0.0208 (4) | 0.0291 (5) | 0.0093 (3) | 0.0135 (4) | 0.0086 (3) |
C8 | 0.0266 (4) | 0.0205 (4) | 0.0287 (4) | 0.0104 (3) | 0.0138 (4) | 0.0074 (3) |
C9 | 0.0465 (6) | 0.0367 (6) | 0.0250 (5) | 0.0145 (5) | 0.0155 (5) | 0.0156 (4) |
C10 | 0.0513 (8) | 0.0411 (7) | 0.0227 (5) | −0.0034 (6) | 0.0091 (5) | 0.0032 (5) |
C11 | 0.0240 (4) | 0.0223 (4) | 0.0260 (4) | 0.0085 (3) | 0.0120 (3) | 0.0081 (3) |
C12 | 0.0229 (4) | 0.0209 (4) | 0.0273 (4) | 0.0069 (3) | 0.0101 (3) | 0.0096 (3) |
C13 | 0.0272 (4) | 0.0211 (4) | 0.0277 (4) | 0.0069 (3) | 0.0113 (4) | 0.0115 (3) |
C14 | 0.0255 (4) | 0.0256 (4) | 0.0253 (4) | 0.0031 (4) | 0.0096 (4) | 0.0116 (4) |
C15 | 0.0223 (4) | 0.0347 (5) | 0.0312 (5) | 0.0082 (4) | 0.0119 (4) | 0.0135 (4) |
C16 | 0.0261 (5) | 0.0296 (5) | 0.0332 (5) | 0.0123 (4) | 0.0142 (4) | 0.0111 (4) |
C17 | 0.0375 (6) | 0.0260 (5) | 0.0690 (9) | 0.0155 (5) | 0.0212 (6) | 0.0212 (6) |
C18 | 0.0262 (5) | 0.0436 (7) | 0.0430 (7) | −0.0028 (5) | 0.0071 (5) | 0.0105 (6) |
C19 | 0.0303 (5) | 0.0230 (4) | 0.0345 (5) | 0.0138 (4) | 0.0133 (4) | 0.0095 (4) |
Cl1—C19 | 1.8246 (12) | C9—H9A | 0.9800 |
O1—C3 | 1.3696 (11) | C9—H9B | 0.9800 |
O1—C9 | 1.4257 (13) | C9—H9C | 0.9800 |
O2—C4 | 1.3646 (11) | C10—H10A | 0.9800 |
O2—C10 | 1.4257 (14) | C10—H10B | 0.9800 |
O3—C13 | 1.3686 (13) | C10—H10C | 0.9800 |
O3—C17 | 1.4284 (15) | C11—C16 | 1.3932 (14) |
O4—C14 | 1.3703 (12) | C11—C12 | 1.4102 (14) |
O4—C18 | 1.4259 (16) | C12—C13 | 1.3903 (13) |
C1—C6 | 1.3978 (14) | C12—H12 | 0.9500 |
C1—C2 | 1.4102 (13) | C13—C14 | 1.4096 (15) |
C1—C7 | 1.4735 (13) | C14—C15 | 1.3850 (16) |
C2—C3 | 1.3851 (13) | C15—C16 | 1.4006 (15) |
C2—H2 | 0.9500 | C15—H15 | 0.9500 |
C3—C4 | 1.4118 (13) | C16—H16 | 0.9500 |
C4—C5 | 1.3884 (14) | C17—H17A | 0.9800 |
C5—C6 | 1.3982 (14) | C17—H17B | 0.9800 |
C5—H5 | 0.9500 | C17—H17C | 0.9800 |
C6—H6 | 0.9500 | C18—H18A | 0.9800 |
C7—C8 | 1.3507 (14) | C18—H18B | 0.9800 |
C7—H7 | 0.9500 | C18—H18C | 0.9800 |
C8—C11 | 1.4885 (13) | C19—H19A | 0.9900 |
C8—C19 | 1.4985 (14) | C19—H19B | 0.9900 |
C3—O1—C9 | 117.06 (8) | H10A—C10—H10C | 109.5 |
C4—O2—C10 | 116.49 (9) | H10B—C10—H10C | 109.5 |
C13—O3—C17 | 116.71 (8) | C16—C11—C12 | 118.56 (9) |
C14—O4—C18 | 117.65 (10) | C16—C11—C8 | 122.03 (9) |
C6—C1—C2 | 118.44 (9) | C12—C11—C8 | 119.41 (9) |
C6—C1—C7 | 118.40 (9) | C13—C12—C11 | 120.69 (9) |
C2—C1—C7 | 123.15 (9) | C13—C12—H12 | 119.7 |
C3—C2—C1 | 120.70 (9) | C11—C12—H12 | 119.7 |
C3—C2—H2 | 119.6 | O3—C13—C12 | 124.19 (9) |
C1—C2—H2 | 119.6 | O3—C13—C14 | 115.67 (9) |
O1—C3—C2 | 124.59 (8) | C12—C13—C14 | 120.09 (9) |
O1—C3—C4 | 115.14 (8) | O4—C14—C15 | 125.49 (10) |
C2—C3—C4 | 120.27 (8) | O4—C14—C13 | 115.14 (10) |
O2—C4—C5 | 125.05 (9) | C15—C14—C13 | 119.37 (9) |
O2—C4—C3 | 115.69 (8) | C14—C15—C16 | 120.43 (9) |
C5—C4—C3 | 119.26 (9) | C14—C15—H15 | 119.8 |
C4—C5—C6 | 120.30 (9) | C16—C15—H15 | 119.8 |
C4—C5—H5 | 119.8 | C11—C16—C15 | 120.85 (10) |
C6—C5—H5 | 119.8 | C11—C16—H16 | 119.6 |
C5—C6—C1 | 120.91 (9) | C15—C16—H16 | 119.6 |
C5—C6—H6 | 119.5 | O3—C17—H17A | 109.5 |
C1—C6—H6 | 119.5 | O3—C17—H17B | 109.5 |
C8—C7—C1 | 129.40 (9) | H17A—C17—H17B | 109.5 |
C8—C7—H7 | 115.3 | O3—C17—H17C | 109.5 |
C1—C7—H7 | 115.3 | H17A—C17—H17C | 109.5 |
C7—C8—C11 | 120.60 (9) | H17B—C17—H17C | 109.5 |
C7—C8—C19 | 122.58 (9) | O4—C18—H18A | 109.5 |
C11—C8—C19 | 116.81 (9) | O4—C18—H18B | 109.5 |
O1—C9—H9A | 109.5 | H18A—C18—H18B | 109.5 |
O1—C9—H9B | 109.5 | O4—C18—H18C | 109.5 |
H9A—C9—H9B | 109.5 | H18A—C18—H18C | 109.5 |
O1—C9—H9C | 109.5 | H18B—C18—H18C | 109.5 |
H9A—C9—H9C | 109.5 | C8—C19—Cl1 | 111.00 (7) |
H9B—C9—H9C | 109.5 | C8—C19—H19A | 109.4 |
O2—C10—H10A | 109.5 | Cl1—C19—H19A | 109.4 |
O2—C10—H10B | 109.5 | C8—C19—H19B | 109.4 |
H10A—C10—H10B | 109.5 | Cl1—C19—H19B | 109.4 |
O2—C10—H10C | 109.5 | H19A—C19—H19B | 108.0 |
C6—C1—C2—C3 | 3.52 (14) | C19—C8—C11—C16 | 40.25 (14) |
C7—C1—C2—C3 | −177.57 (9) | C7—C8—C11—C12 | 41.63 (14) |
C9—O1—C3—C2 | −4.98 (15) | C19—C8—C11—C12 | −139.31 (10) |
C9—O1—C3—C4 | 174.42 (9) | C16—C11—C12—C13 | −0.77 (15) |
C1—C2—C3—O1 | 178.30 (9) | C8—C11—C12—C13 | 178.80 (9) |
C1—C2—C3—C4 | −1.07 (14) | C17—O3—C13—C12 | −4.36 (16) |
C10—O2—C4—C5 | 9.86 (16) | C17—O3—C13—C14 | 178.12 (10) |
C10—O2—C4—C3 | −169.56 (11) | C11—C12—C13—O3 | −176.96 (10) |
O1—C3—C4—O2 | −1.71 (13) | C11—C12—C13—C14 | 0.45 (15) |
C2—C3—C4—O2 | 177.72 (9) | C18—O4—C14—C15 | −2.36 (16) |
O1—C3—C4—C5 | 178.83 (9) | C18—O4—C14—C13 | 176.73 (10) |
C2—C3—C4—C5 | −1.74 (14) | O3—C13—C14—O4 | −0.86 (13) |
O2—C4—C5—C6 | −177.37 (10) | C12—C13—C14—O4 | −178.48 (9) |
C3—C4—C5—C6 | 2.03 (15) | O3—C13—C14—C15 | 178.29 (9) |
C4—C5—C6—C1 | 0.48 (16) | C12—C13—C14—C15 | 0.67 (15) |
C2—C1—C6—C5 | −3.23 (15) | O4—C14—C15—C16 | 177.60 (10) |
C7—C1—C6—C5 | 177.80 (9) | C13—C14—C15—C16 | −1.45 (15) |
C6—C1—C7—C8 | −148.25 (11) | C12—C11—C16—C15 | −0.01 (15) |
C2—C1—C7—C8 | 32.84 (16) | C8—C11—C16—C15 | −179.57 (10) |
C1—C7—C8—C11 | −176.75 (9) | C14—C15—C16—C11 | 1.13 (16) |
C1—C7—C8—C19 | 4.24 (17) | C7—C8—C19—Cl1 | −99.79 (10) |
C7—C8—C11—C16 | −138.81 (11) | C11—C8—C19—Cl1 | 81.17 (10) |
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2···Cl1 | 0.95 | 2.73 | 3.5800 (10) | 150 |
C12—H12···O1i | 0.95 | 2.57 | 3.5130 (13) | 170 |
C17—H17B···Cl1ii | 0.98 | 2.82 | 3.7947 (12) | 173 |
C17—H17C···O2i | 0.98 | 2.59 | 3.5640 (16) | 174 |
Symmetry codes: (i) −x+1, −y+1, −z; (ii) x, y+1, z. |
Experimental details
Crystal data | |
Chemical formula | C19H21ClO4 |
Mr | 348.81 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 173 |
a, b, c (Å) | 9.2561 (1), 10.0669 (2), 11.5351 (2) |
α, β, γ (°) | 104.620 (1), 108.441 (1), 109.692 (1) |
V (Å3) | 879.06 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.24 |
Crystal size (mm) | 0.52 × 0.40 × 0.18 |
Data collection | |
Diffractometer | Siemens SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2002) |
Tmin, Tmax | 0.887, 0.959 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 14932, 5768, 4859 |
Rint | 0.022 |
(sin θ/λ)max (Å−1) | 0.736 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.113, 1.02 |
No. of reflections | 5768 |
No. of parameters | 242 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.43, −0.38 |
Computer programs: SMART (Siemens, 1995), SAINT (Siemens, 1995), SAINT and SADABS (Sheldrick, 2002), SHELXTL (Bruker, 1997), SHELXTL, DIAMOND (Brandenburg, 2000).
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2···Cl1 | 0.95 | 2.73 | 3.5800 (10) | 150 |
C12—H12···O1i | 0.95 | 2.57 | 3.5130 (13) | 170 |
C17—H17B···Cl1ii | 0.98 | 2.82 | 3.7947 (12) | 173 |
C17—H17C···O2i | 0.98 | 2.59 | 3.5640 (16) | 174 |
Symmetry codes: (i) −x+1, −y+1, −z; (ii) x, y+1, z. |
Stereoisomers of α-chloromethyl-3,3',4,4'-tetramethoxystilbene, (I), are present in reaction mixtures obtained on refluxing of the lignin model 1,2-bis(3,4-dimethoxyphenyl)-1,3-propanediol with 0.2 M hydrogen chloride in dioxane–water 9:1 (Li et al., 1997). The identification of the compounds was based on comparisons with synthetic samples (Li et al., 1997). The synthetic method applied gave a mixture of stereoisomers from which the Z isomer, (Ib), could be isolated in crystalline form (Li et al., 1997). The crystalline form of the E isomer, (Ia), has been described earlier (Russel & Hunziker, 1969). To verify the steric assignments of the E, (Ia), and Z, (Ib), isomers of (I), we have determined the crystal structure of (Ib).
A perspective drawing of (Ib) and the atom-numbering scheme is shown in Fig. 1. In the crystal structure, (Ib) adopts a non-planar conformation. The torsion angles C2—C1—C7—C8 and C7—C8—C11—C12 are 32.84 (16) and 41.63 (14)°, respectively. The angle between the aromatic ring planes is 75.74 (6)°. The ethylene group and the atoms attached to it (C1, C11 and C19) are nearly coplanar [maximum deviation 0.028 (1) Å]. The angles between the least-squares plane and the aromatic ring planes C1–C6 and C11–C16 are 35.29 (6) and 40.60 (6)°, respectively. The conformations of the α-substituted stilbenes (Z)-2,3-bis(3,4-dimethoxyphenyl)-2-propen-1-ol (Stomberg et al., 1995) and methyl (E)-p-[2-(2,3-dihydro-3,3-dimethyl-5-benzofuranyl)-1-propenyl]benzoate (Gale et al., 1990) exhibit similarities to that of (Ib). Stilbenes with trans-orientated aryl groups lacking an α-substituent, such as (E)-4,4'-dimethoxystilbene (Theocharis et al., 1984), are planar or nearly planar.
There are weak C—H···O and C—H···Cl hydrogen bonds present in the crystal structure of (Ib) (Table 1). There are two C–H···O hydrogen bonds formed by dimers of molecules related by an inversion center (Fig. 2). On the first-level graph-set, following Bernstein et al. (1995) and Grell et al. (1999), the hydrogen bond C12–H12···O1i [symmetry code: (i) 1 − x, 1 − y,-z] forms an R22(18) ring, and the hydrogen bond C17–H17C···O2i forms an R22(26) ring. The intramolecular hydrogen bond C2–H2···Cl1 forms an S(7) string, while the intermolecular hydrogen bond C17–H17B···Cl1ii [symmetry code: (ii) x, 1 + y, z] forms a C(9) chain, connecting the molecules in the b direction (Fig. 3). On the second-level graph-set, rings R22(10), R22(22), R44(24), R44(28), R44(36) and R44(44) were recognized. The assignment of graph-set descriptors were performed using PLUTO, as described by Motherwell et al. (1999).
The methylene group signal is located at δ 4.44 in the 1H NMR spectrum of the E isomer, (Ia), and at δ 4.65 in the 1H NMR spectrum of Z isomer, (Ib) (Li et al. 1997). The methylene group signal of the E isomer, (IIa) (δ 4.89), is also located at higher field than that of the Z isomer, (IIb) (δ 5.16) (Li et al. 1997). Stereoisomers of (III) have been described by Gellerstedt et al. (1976) but steric assignments were not reported. Based on 1H NMR spectral comparisons with (I) and (II) it is possible to conclude that the isomer denoted `1. Form' by Gellerstedt et al. (1976) is (IIIb) (the methylene group signal is located at δ 4.46) and that the isomer denoted `2. Form' by these authors is (IIIa) (the methylene group signal is located at δ 4.16).