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Annealing of the quenched ibuprofen at 258 K yielded a new crystalline form, called phase II. Powder X-ray diffraction patterns of this phase II were recorded with a laboratory diffractometer equipped with an INEL G3000 goniometer and a curved position-sensitive detector CPS120. The starting structural model was found by a Monte-Carlo simulated annealing method. The final structure was obtained through Rietveld refinements with rigid-body constraints for the phenyl group and soft restraints on the other interatomic bond lengths and bond angles. The cell volume is 5% larger than that of the conventional phase I at 258 K. It is also shown that the orientation of the propanoic acid group is drastically changed with respect to phase I, leading to strong modifications of the orientation of the O—H...O hydrogen bonds with respect to the chains of dimers. These structural considerations could explain the metastable character of this phase II.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768109047363/ws5072sup1.cif
Contains datablocks global, ibuprofen

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108768109047363/ws5072ibuprofensup2.rtv
Contains datablock ibuprofen

CCDC reference: 774097

Computing details top

Program(s) used to refine structure: FULLPROF.

(ibuprofen) top
Crystal data top
C13H18O2V = 1272.03 (18) Å3
Mr = 206.28Z = 4
Monoclinic, P21/cDx = 1.077 Mg m3
Hall symbol: -P 2ybcX-ray radiation, λ = 1.540560 Å
a = 12.3794 (9) ŵ = 0.56 mm1
b = 5.8723 (5) ÅT = 258 K
c = 17.5615 (15) Åwhite
β = 94.873 (4)°
Data collection top
Inel CPS120
diffractometer
Data collection mode: transmission
Radiation source: X-ray tubeScan method: Stationary detector
Specimen mounting: 0.7 mm diameter Lindemann capillary2θfixed = 0.2-113.8
Refinement top
Rp = 0.040Profile function: pseudo-Voigt
Rwp = 0.05659 parameters
Rexp = 0.12635 restraints
RBragg = 0.058Background function: linear interpolation between selected points
7579 data points
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.5572 (6)0.6766 (19)0.4158 (4)0.00000*
C20.6059 (6)0.8680 (12)0.3731 (4)0.00000*
C30.6963 (8)0.967 (2)0.4240 (6)0.00000*
C40.6641 (11)0.734 (4)0.3179 (5)0.00000*
C50.7604 (12)0.631 (4)0.3441 (7)0.00000*
C60.8130 (12)0.489 (3)0.2963 (5)0.00000*
C70.7692 (11)0.450 (3)0.2225 (6)0.00000*
C80.6729 (11)0.554 (3)0.1962 (6)0.00000*
C90.6204 (11)0.696 (3)0.2439 (5)0.00000*
C100.8061 (12)0.2511 (11)0.1767 (6)0.00000*
C110.8511 (5)0.3890 (10)0.1113 (4)0.00000*
C120.9146 (10)0.1809 (16)0.0890 (7)0.00000*
C130.9565 (7)0.507 (2)0.1420 (7)0.00000*
O10.6004 (8)0.6812 (17)0.4845 (4)0.00000*
O20.4615 (5)0.6338 (17)0.4159 (5)0.00000*
H10.542520.594600.515770.00000*
H20.542470.952110.345720.00000*
H30.694570.931090.477650.00000*
H40.762450.931090.402580.00000*
H50.685091.143510.422140.00000*
H60.790910.644120.398290.00000*
H70.881850.419050.318020.00000*
H80.642660.525230.143030.00000*
H90.552730.764360.221480.00000*
H100.751860.176340.144430.00000*
H110.853720.146440.210910.00000*
H120.791160.420360.072300.00000*
H130.979500.161310.124760.00000*
H140.946230.207220.040490.00000*
H150.860320.064550.067440.00000*
H160.991600.588680.102120.00000*
H170.989380.397910.186710.00000*
H180.950010.640610.186710.00000*
 

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