Redetermination and H-atom refinement of (S)-(+)-ibuprofen

Hansen, L.K.; Perlovich, G.L.; Bauer-Brandl, A.

doi:10.1107/S160053680301451X

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Redetermination and H-atom refinement of (S)-(+)-ibuprofen

L. K. Hansen, G. L. Perlovich and A. Bauer-Brandl

The crystal structure of (S)-(+)-ibuprofen, C₁₃H₁₈O₂, has been redetermined. It crystallizes in the monoclinic space group P2₁ with two molecules in the asymmetric unit, giving a cyclic hydrogen-bonded dimer. All the H atoms were located from difference maps and refined isotropically.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S160053680301451X/cf6266sup1.cif Contains datablocks global, I
	Structure factor file (CIF format) https://doi.org/10.1107/S160053680301451X/cf6266Isup2.hkl Contains datablock I

CCDC reference: 222894

checkCIF report

Key indicators

Single-crystal X-ray study
T = 298 K
Mean (C-C) = 0.005 Å
R factor = 0.038
wR factor = 0.105
Data-to-parameter ratio = 7.0

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT390_ALERT_3_B Deviating Methyl C13B    X-C-H Bond Angle ......      98.00 Deg.

Alert level C
PLAT089_ALERT_3_C Poor Data / Parameter Ratio (Zmax .LT. 18) .....       7.00
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.28 Ratio
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.75 Ratio
PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....        C1A
PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....       C11A
PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....        C1B
PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....       C11B
PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          5
PLAT351_ALERT_3_C Long    C-H Bond (0.96A)   C12A   -   H131     =       1.12 Ang.
PLAT351_ALERT_3_C Long    C-H Bond (0.96A)   C3B    -   H3B3     =       1.14 Ang.
PLAT351_ALERT_3_C Long    C-H Bond (0.96A)   C12B   -   H126     =       1.12 Ang.
PLAT355_ALERT_3_C Long    O-H Bond (0.82A)   O1B    -   H1BO     =       1.07 Ang.
PLAT390_ALERT_3_C Deviating Methyl C12B    X-C-H Bond Angle ......     117.00 Deg.
PLAT390_ALERT_3_C Deviating Methyl C12B    X-C-H Bond Angle ......     100.00 Deg.
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          8
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.  #          1
              C13 H18 O2

Alert level G
REFLT03_ALERT_4_G 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.
           From the CIF: _diffrn_reflns_theta_max           26.96
           From the CIF: _reflns_number_total               2910
           Count of symmetry unique reflns         2909
           Completeness (_total/calc)            100.03%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         1
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present           no

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
  17 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   4 ALERT type 2 Indicator that the structure model may be wrong or deficient
  11 ALERT type 3 Indicator that the structure quality may be low
   4 ALERT type 4 Improvement, methodology, query or suggestion

Comment top

The structure of racemic ibuprofen (IBP), (I), has been well described both by X-ray diffraction at 298 K (McConnell, 1974) and single-crystal pulsed neutron diffraction at 100 K (Shankland et al., 1997). The structure of (S)-ibuprofen has also been solved by X-ray diffraction (Freer et al., 1993). However, in contrast to the racemate, the quality and paucity of data did not allow the determination of the positions of the H atoms. It should be noted that the lack of this information is a serious obstacle for a logical classification of the hydrogen-bond topology of the compound, and for the calculation of crystal-lattice energy by methods which are sensitive to the geometry of hydrogen bonding (e.g. Gavezzotti & Filippini, 1997). With this background, the main aim of this work has been to find and refine the positions of the H atoms.

A view of the two crystallographically independent (S)-IBP molecules, with the atomic numbering, is presented in Fig. 1. The parameters of the hydrogen-bond geometry for both the racemic and S-enantiomer IBP are shown in Table 1 (Taylor & Kennard, 1982). As there are two independent molecules in the asymmetric unit, the two hydrogen bonds are not geometrically equivalent; one of them is shorter than the other. Comparison of these data gives the following conclusions: (a) the hydrogen bond in the racemate is more linear than in the S-enantiomer; (b) one of the O···O distances in (S)-IBP is essentially the same as that in the racemate, but the other is longer; (c) the H···O distance in the racemate is an average of the analogous parameters of the S-enantiomer. The conformations of the S-enantiomer molecules are different; the main parameters characterizing these differences are presented in Table 2, together with corresponding ones for the racemate. As can be seen, molecule A in the S-enantiomer structure has approximately the same conformation as the IBP molecule in the racemate.

Experimental top

(S)-IBP single crystals were grown by slow evaporation from an n-heptanol solution.

Computing details top

Data collection: CAD-4-PC Software (Enraf–Nonius, 1992); cell refinement: CELDIM in CAD-4-PC Software; data reduction: XCAD4 (McArdle & Higgins, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEX (McArdle, 1995); software used to prepare material for publication: OSCAIL (Version 9; McArdle, 1993).

Figures top

Fig. 1. A view of the (S)-(+)-ibuprofen dimer with the atomic numbering scheme. Displacement ellipsoids are drawn at the 20% probability level.

(I) top

Crystal data top

C₁₃H₁₈O₂	F(000) = 448
M_r = 206.27	D_x = 1.098 Mg m⁻³
Monoclinic, P2₁	Mo Kα radiation, λ = 0.71069 Å
a = 12.456 (4) Å	Cell parameters from 25 reflections
b = 8.0362 (11) Å	θ = 14–20°
c = 13.533 (3) Å	µ = 0.07 mm⁻¹
β = 112.86 (2)°	T = 298 K
V = 1248.2 (5) Å³	Block, colourless
Z = 4	0.40 × 0.40 × 0.30 mm

Data collection top

Enraf-Nonius CAD-4 diffractometer	R_int = 0.019
Radiation source: fine-focus sealed tube	θ_max = 27.0°, θ_min = 1.6°
Graphite monochromator	h = 0→15
ω–2θ scans	k = −1→10
3086 measured reflections	l = −17→15
2910 independent reflections	3 standard reflections every 120 min
1683 reflections with I > 2σ(I)	intensity decay: 2%

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)] = 0.039	All H-atom parameters refined
wR(F²) = 0.105	w = 1/[σ²(F_o²) + (0.0583P)²] where P = (F_o² + 2F_c²)/3
S = 0.98	(Δ/σ)_max = 0.002
2910 reflections	Δρ_max = 0.12 e Å⁻³
416 parameters	Δρ_min = −0.11 e Å⁻³
1 restraint	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.016 (3)

Crystal data top

C₁₃H₁₈O₂	V = 1248.2 (5) Å³
M_r = 206.27	Z = 4
Monoclinic, P2₁	Mo Kα radiation
a = 12.456 (4) Å	µ = 0.07 mm⁻¹
b = 8.0362 (11) Å	T = 298 K
c = 13.533 (3) Å	0.40 × 0.40 × 0.30 mm
β = 112.86 (2)°

Data collection top

Enraf-Nonius CAD-4 diffractometer	R_int = 0.019
3086 measured reflections	3 standard reflections every 120 min
2910 independent reflections	intensity decay: 2%
1683 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.039	1 restraint
wR(F²) = 0.105	All H-atom parameters refined
S = 0.98	Δρ_max = 0.12 e Å⁻³
2910 reflections	Δρ_min = −0.11 e Å⁻³
416 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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

10.1787 (0.0112) x + 4.6284 (0.0096) y − 4.5783 (0.0166) z = 3.3305 (0.0116)

* −0.0072 (0.0022) C4A * 0.0049 (0.0026) C5A * 0.0010 (0.0026) C6A * −0.0047 (0.0023) C7A * 0.0024 (0.0024) C8A * 0.0036 (0.0023) C9A 1.4672 (0.0056) C1A 0.0366 (0.0051) C2A −0.7949 (0.0064) C3A 2.1128 (0.0059) O1A 2.0110 (0.0057) O2A −0.0771 (0.0056) C10A −1.4843 (0.0060) C11A −1.4790 (0.0092) C12A −2.2935 (0.0070) C13A

Rms deviation of fitted atoms = 0.0044

9.9282 (0.0098) x + 4.8474 (0.0078) y − 4.5545 (0.0147) z = 9.7391 (0.0062)

Angle to previous plane (with approximate e.s.d.) = 1.98 (0.18)

* 0.0096 (0.0019) C4B * −0.0063 (0.0021) C5B * −0.0037 (0.0021) C6B * 0.0105 (0.0019) C7B * −0.0073 (0.0020) C8B * −0.0027 (0.0020) C9B −1.4004 (0.0051) C1B 0.0314 (0.0046) C2B 0.7091 (0.0063) C3B −2.0812 (0.0050) O1B −1.8909 (0.0052) O2B 0.0649 (0.0047) C10B 1.4528 (0.0055) C11B 2.4265 (0.0067) C12B 1.3582 (0.0088) C13B

Rms deviation of fitted atoms = 0.0073

Hydrogen bonds with H.·A < r(A) + 2.000 Angstroms and <DHA > 110 °.

D—H d(D—H) d(H.·A) <DHA d(D.·A) A

O1B—H1BO 1.070 1.579 167.64 2.634 O2A

O1A—H1AO 0.937 1.726 168.97 2.651 O2B

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	U_iso*/U_eq
C4B	0.8401 (2)	0.3199 (3)	0.0314 (2)	0.0497 (7)
O2A	0.58499 (19)	−0.2352 (3)	−0.10390 (18)	0.0757 (6)
O1A	0.4640 (2)	−0.0661 (4)	−0.2241 (2)	0.0890 (8)
O1B	0.7685 (2)	−0.0391 (3)	−0.04780 (18)	0.0710 (6)
O2B	0.6486 (2)	0.1313 (3)	−0.16958 (17)	0.0840 (7)
C7B	0.8336 (2)	0.4998 (3)	0.2083 (2)	0.0493 (7)
C9B	0.7668 (2)	0.4546 (4)	0.0175 (2)	0.0547 (7)
C6B	0.9054 (3)	0.3626 (4)	0.2220 (2)	0.0604 (8)
C8B	0.7632 (2)	0.5422 (4)	0.1041 (2)	0.0548 (7)
C2B	0.8429 (3)	0.2278 (4)	−0.0655 (2)	0.0590 (8)
C5B	0.9085 (3)	0.2746 (4)	0.1358 (2)	0.0599 (8)
C10B	0.8355 (3)	0.5965 (4)	0.3034 (2)	0.0614 (8)
C11B	0.9402 (3)	0.7128 (5)	0.3508 (2)	0.0688 (9)
C1B	0.7446 (3)	0.1014 (4)	−0.0998 (2)	0.0547 (7)
C12B	0.9347 (5)	0.8545 (7)	0.2759 (4)	0.1068 (17)
C3B	0.9591 (3)	0.1463 (6)	−0.0477 (4)	0.0835 (11)
C13B	0.9486 (6)	0.7781 (7)	0.4595 (4)	0.1045 (15)
H3B3	0.990 (3)	0.047 (6)	0.017 (3)	0.117 (14)*
H133	0.170 (5)	−0.953 (8)	−0.765 (4)	0.16 (2)*
H123	0.363 (5)	−1.006 (10)	−0.537 (4)	0.19 (3)*
H1BO	0.688 (4)	−0.106 (6)	−0.077 (3)	0.113 (13)*
H132	0.225 (4)	−0.765 (7)	−0.783 (4)	0.129 (18)*
H131	0.328 (4)	−0.925 (7)	−0.732 (4)	0.16 (2)*
H126	0.865 (6)	0.933 (12)	0.286 (6)	0.24 (4)*
H3B2	0.949 (2)	0.094 (4)	−0.118 (2)	0.072 (9)*
H2B	0.821 (2)	0.309 (4)	−0.128 (2)	0.064 (8)*
H3B1	1.020 (4)	0.236 (8)	−0.031 (4)	0.144 (18)*
H125	0.913 (4)	0.826 (6)	0.200 (4)	0.114 (14)*
H124	1.015 (5)	0.917 (9)	0.310 (4)	0.16 (2)*
H103	0.840 (2)	0.513 (4)	0.360 (2)	0.068 (9)*
H104	0.761 (3)	0.665 (4)	0.279 (2)	0.065 (9)*
H6B	0.957 (3)	0.326 (4)	0.298 (3)	0.075 (10)*
H136	0.883 (4)	0.850 (7)	0.435 (4)	0.14 (2)*
H8B	0.712 (3)	0.632 (5)	0.093 (2)	0.073 (9)*
H134	1.009 (3)	0.841 (5)	0.486 (3)	0.074 (11)*
H5B	0.966 (2)	0.183 (4)	0.152 (2)	0.071 (9)*
H9B	0.712 (3)	0.480 (5)	−0.053 (3)	0.093 (11)*
H135	0.949 (5)	0.679 (10)	0.516 (5)	0.19 (3)*
H11B	1.020 (3)	0.655 (4)	0.3544 (19)	0.065 (8)*
H3A3	0.332 (3)	−0.522 (6)	−0.127 (3)	0.108 (12)*
H11A	0.195 (4)	−0.741 (6)	−0.642 (3)	0.111 (14)*
H101	0.434 (3)	−0.741 (5)	−0.577 (3)	0.088 (12)*
H3A2	0.403 (3)	−0.385 (6)	−0.050 (3)	0.104 (14)*
H102	0.348 (3)	−0.600 (6)	−0.645 (3)	0.115 (15)*
H121	0.298 (3)	−0.904 (6)	−0.474 (3)	0.108 (12)*
H122	0.210 (4)	−1.024 (7)	−0.584 (3)	0.122 (14)*
H6A	0.257 (3)	−0.404 (6)	−0.563 (3)	0.105 (12)*
H2A	0.326 (3)	−0.265 (5)	−0.217 (3)	0.096 (12)*
H8A	0.500 (3)	−0.738 (5)	−0.376 (2)	0.074 (9)*
H9A	0.500 (3)	−0.598 (4)	−0.227 (3)	0.058 (8)*
H5A	0.271 (3)	−0.283 (5)	−0.398 (2)	0.074 (10)*
H1AO	0.533 (4)	−0.007 (8)	−0.208 (4)	0.16 (2)*
H3A1	0.481 (4)	−0.502 (6)	−0.073 (3)	0.131 (16)*
C1A	0.4879 (3)	−0.2052 (4)	−0.1705 (2)	0.0613 (8)
C2A	0.3900 (3)	−0.3274 (4)	−0.1995 (3)	0.0680 (9)
C3A	0.4028 (4)	−0.4412 (7)	−0.1044 (4)	0.0899 (13)
C4A	0.3837 (2)	−0.4215 (4)	−0.2990 (2)	0.0592 (8)
C5A	0.3135 (3)	−0.3645 (5)	−0.4000 (3)	0.0776 (10)
C6A	0.3095 (3)	−0.4468 (5)	−0.4913 (3)	0.0795 (10)
C7A	0.3752 (3)	−0.5870 (4)	−0.4856 (3)	0.0666 (9)
C8A	0.4460 (3)	−0.6415 (5)	−0.3850 (3)	0.0685 (9)
C9A	0.4501 (3)	−0.5605 (4)	−0.2941 (3)	0.0659 (9)
C10A	0.3649 (4)	−0.6796 (6)	−0.5864 (3)	0.0820 (12)
C11A	0.2651 (3)	−0.8032 (5)	−0.6258 (3)	0.0756 (10)
C13A	0.2856 (5)	−0.9476 (6)	−0.5496 (4)	0.0920 (13)
C12A	0.2441 (5)	−0.8664 (9)	−0.7376 (3)	0.1028 (14)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C4B	0.0532 (14)	0.0418 (16)	0.0556 (16)	−0.0049 (13)	0.0229 (12)	−0.0050 (13)
O2A	0.0602 (12)	0.0611 (14)	0.0891 (14)	−0.0027 (11)	0.0106 (11)	0.0094 (12)
O1A	0.0719 (16)	0.0732 (17)	0.0998 (18)	0.0059 (14)	0.0094 (14)	0.0200 (15)
O1B	0.0699 (14)	0.0505 (13)	0.0825 (14)	0.0005 (11)	0.0186 (11)	0.0060 (12)
O2B	0.0822 (14)	0.0658 (15)	0.0799 (14)	−0.0034 (13)	0.0051 (13)	0.0127 (13)
C7B	0.0488 (14)	0.0476 (16)	0.0541 (16)	−0.0070 (13)	0.0227 (12)	−0.0038 (14)
C9B	0.0545 (16)	0.0519 (17)	0.0523 (16)	0.0047 (15)	0.0148 (13)	0.0004 (14)
C6B	0.0727 (19)	0.0566 (18)	0.0504 (17)	0.0013 (17)	0.0224 (15)	0.0047 (16)
C8B	0.0554 (16)	0.0487 (16)	0.0566 (16)	0.0090 (15)	0.0178 (13)	0.0005 (14)
C2B	0.0716 (19)	0.0511 (19)	0.0646 (18)	−0.0018 (16)	0.0379 (15)	−0.0023 (16)
C5B	0.0644 (17)	0.0454 (17)	0.0676 (19)	0.0142 (15)	0.0231 (15)	0.0061 (15)
C10B	0.0675 (19)	0.064 (2)	0.0547 (16)	−0.0061 (17)	0.0259 (14)	−0.0025 (17)
C11B	0.075 (2)	0.065 (2)	0.0639 (19)	−0.0088 (18)	0.0246 (16)	−0.0154 (17)
C1B	0.0708 (18)	0.0455 (17)	0.0530 (16)	0.0069 (15)	0.0296 (15)	−0.0022 (14)
C12B	0.137 (4)	0.098 (4)	0.086 (3)	−0.047 (3)	0.043 (3)	−0.009 (3)
C3B	0.079 (2)	0.080 (3)	0.111 (3)	−0.006 (2)	0.058 (2)	−0.028 (3)
C13B	0.134 (4)	0.093 (3)	0.077 (3)	−0.022 (4)	0.030 (3)	−0.030 (3)
C1A	0.0580 (18)	0.059 (2)	0.0647 (18)	0.0051 (16)	0.0210 (16)	−0.0113 (18)
C2A	0.0517 (17)	0.069 (2)	0.084 (2)	0.0060 (17)	0.0268 (16)	−0.0114 (19)
C3A	0.096 (3)	0.105 (3)	0.085 (3)	−0.027 (3)	0.053 (2)	−0.014 (3)
C4A	0.0421 (14)	0.059 (2)	0.0703 (19)	−0.0021 (14)	0.0149 (13)	−0.0007 (16)
C5A	0.076 (2)	0.059 (2)	0.087 (3)	0.014 (2)	0.0197 (19)	−0.003 (2)
C6A	0.088 (2)	0.069 (2)	0.064 (2)	0.002 (2)	0.0107 (18)	0.006 (2)
C7A	0.0706 (19)	0.063 (2)	0.069 (2)	−0.0111 (17)	0.0302 (16)	−0.0028 (18)
C8A	0.0582 (18)	0.068 (2)	0.073 (2)	0.0080 (18)	0.0184 (16)	−0.0084 (19)
C9A	0.0570 (17)	0.065 (2)	0.0634 (19)	0.0084 (17)	0.0098 (15)	−0.0041 (18)
C10A	0.089 (3)	0.093 (3)	0.071 (2)	−0.017 (2)	0.038 (2)	−0.006 (2)
C11A	0.073 (2)	0.086 (3)	0.0643 (19)	0.000 (2)	0.0234 (16)	−0.007 (2)
C13A	0.106 (3)	0.084 (3)	0.084 (3)	−0.013 (3)	0.036 (3)	−0.003 (2)
C12A	0.105 (3)	0.126 (4)	0.073 (2)	−0.010 (3)	0.030 (2)	−0.022 (3)

Geometric parameters (Å, º) top

C4B—C9B	1.382 (4)	C13B—H136	0.95 (5)
C4B—C5B	1.385 (4)	C13B—H134	0.86 (4)
C4B—C2B	1.517 (4)	C13B—H135	1.10 (7)
O2A—C1A	1.219 (3)	C1A—C2A	1.496 (5)
O1A—C1A	1.302 (4)	C2A—C4A	1.519 (4)
O1A—H1AO	0.94 (6)	C2A—C3A	1.536 (6)
O1B—C1B	1.302 (4)	C2A—H2A	0.89 (4)
O1B—H1BO	1.07 (5)	C3A—H3A3	1.05 (4)
O2B—C1B	1.226 (3)	C3A—H3A2	0.87 (4)
C7B—C8B	1.383 (4)	C3A—H3A1	1.03 (5)
C7B—C6B	1.386 (4)	C4A—C9A	1.377 (4)
C7B—C10B	1.495 (4)	C4A—C5A	1.384 (4)
C9B—C8B	1.382 (4)	C5A—C6A	1.385 (5)
C9B—H9B	0.96 (3)	C5A—H5A	0.85 (4)
C6B—C5B	1.378 (4)	C6A—C7A	1.376 (5)
C6B—H6B	1.03 (4)	C6A—H6A	1.00 (4)
C8B—H8B	0.93 (4)	C7A—C8A	1.375 (4)
C2B—C1B	1.518 (4)	C7A—C10A	1.515 (5)
C2B—C3B	1.521 (5)	C8A—C9A	1.374 (4)
C2B—H2B	1.01 (3)	C8A—H8A	1.00 (4)
C5B—H5B	0.99 (3)	C9A—H9A	0.93 (3)
C10B—C11B	1.529 (4)	C10A—C11A	1.516 (6)
C10B—H103	1.00 (3)	C10A—H101	0.95 (4)
C10B—H104	1.01 (3)	C10A—H102	0.97 (5)
C11B—C12B	1.508 (6)	C11A—C13A	1.506 (6)
C11B—C13B	1.526 (5)	C11A—C12A	1.520 (5)
C11B—H11B	1.08 (3)	C11A—H11A	0.95 (4)
C12B—H126	1.12 (8)	C13A—H123	1.03 (6)
C12B—H125	0.98 (4)	C13A—H121	1.04 (4)
C12B—H124	1.05 (6)	C13A—H122	1.06 (5)
C3B—H3B3	1.14 (5)	C12A—H133	1.09 (6)
C3B—H3B2	1.00 (3)	C12A—H132	0.99 (6)
C3B—H3B1	1.00 (6)	C12A—H131	1.12 (5)

C9B—C4B—C5B	117.1 (3)	H134—C13B—H135	112 (4)
C9B—C4B—C2B	120.0 (3)	O2A—C1A—O1A	121.9 (3)
C5B—C4B—C2B	122.8 (3)	O2A—C1A—C2A	122.5 (3)
C1A—O1A—H1AO	109 (3)	O1A—C1A—C2A	115.5 (3)
C1B—O1B—H1BO	105 (2)	C1A—C2A—C4A	108.3 (3)
C8B—C7B—C6B	116.9 (3)	C1A—C2A—C3A	111.3 (3)
C8B—C7B—C10B	122.8 (3)	C4A—C2A—C3A	113.5 (3)
C6B—C7B—C10B	120.3 (3)	C1A—C2A—H2A	105 (3)
C8B—C9B—C4B	121.4 (3)	C4A—C2A—H2A	108 (2)
C8B—C9B—H9B	120 (2)	C3A—C2A—H2A	110 (2)
C4B—C9B—H9B	119 (2)	C2A—C3A—H3A3	109 (2)
C5B—C6B—C7B	121.7 (3)	C2A—C3A—H3A2	112 (3)
C5B—C6B—H6B	119.4 (19)	H3A3—C3A—H3A2	107 (3)
C7B—C6B—H6B	119.0 (19)	C2A—C3A—H3A1	114 (2)
C9B—C8B—C7B	121.5 (3)	H3A3—C3A—H3A1	113 (4)
C9B—C8B—H8B	119.7 (18)	H3A2—C3A—H3A1	102 (3)
C7B—C8B—H8B	118.8 (17)	C9A—C4A—C5A	116.9 (3)
C4B—C2B—C1B	107.7 (2)	C9A—C4A—C2A	122.6 (3)
C4B—C2B—C3B	114.4 (3)	C5A—C4A—C2A	120.4 (3)
C1B—C2B—C3B	111.4 (3)	C4A—C5A—C6A	120.9 (4)
C4B—C2B—H2B	108.2 (16)	C4A—C5A—H5A	113 (2)
C1B—C2B—H2B	104.5 (16)	C6A—C5A—H5A	126 (2)
C3B—C2B—H2B	110.1 (15)	C7A—C6A—C5A	121.7 (4)
C6B—C5B—C4B	121.3 (3)	C7A—C6A—H6A	119 (2)
C6B—C5B—H5B	116.7 (16)	C5A—C6A—H6A	119 (2)
C4B—C5B—H5B	121.8 (16)	C8A—C7A—C6A	117.1 (3)
C7B—C10B—C11B	113.9 (3)	C8A—C7A—C10A	122.2 (3)
C7B—C10B—H103	106.8 (17)	C6A—C7A—C10A	120.7 (4)
C11B—C10B—H103	107.5 (16)	C9A—C8A—C7A	121.4 (3)
C7B—C10B—H104	107.4 (16)	C9A—C8A—H8A	118.2 (17)
C11B—C10B—H104	109.0 (18)	C7A—C8A—H8A	120.2 (17)
H103—C10B—H104	112 (2)	C8A—C9A—C4A	121.9 (3)
C12B—C11B—C13B	110.9 (4)	C8A—C9A—H9A	120.1 (18)
C12B—C11B—C10B	111.8 (3)	C4A—C9A—H9A	118.0 (18)
C13B—C11B—C10B	110.1 (4)	C7A—C10A—C11A	114.2 (3)
C12B—C11B—H11B	98.8 (16)	C7A—C10A—H101	112 (2)
C13B—C11B—H11B	112.7 (14)	C11A—C10A—H101	106 (2)
C10B—C11B—H11B	112.2 (17)	C7A—C10A—H102	109 (3)
O2B—C1B—O1B	122.4 (3)	C11A—C10A—H102	105 (2)
O2B—C1B—C2B	122.3 (3)	H101—C10A—H102	110 (3)
O1B—C1B—C2B	115.3 (3)	C13A—C11A—C10A	111.5 (4)
C11B—C12B—H126	100 (4)	C13A—C11A—C12A	110.0 (4)
C11B—C12B—H125	117 (3)	C10A—C11A—C12A	111.7 (4)
H126—C12B—H125	110 (4)	C13A—C11A—H11A	117 (3)
C11B—C12B—H124	106 (3)	C10A—C11A—H11A	107 (3)
H126—C12B—H124	109 (5)	C12A—C11A—H11A	99 (2)
H125—C12B—H124	113 (4)	C11A—C13A—H123	112 (4)
C2B—C3B—H3B3	116 (2)	C11A—C13A—H121	110 (3)
C2B—C3B—H3B2	105.4 (17)	H123—C13A—H121	102 (4)
H3B3—C3B—H3B2	109 (3)	C11A—C13A—H122	105 (2)
C2B—C3B—H3B1	108 (3)	H123—C13A—H122	115 (5)
H3B3—C3B—H3B1	109 (4)	H121—C13A—H122	114 (3)
H3B2—C3B—H3B1	109 (3)	C11A—C12A—H133	110 (3)
C11B—C13B—H136	98 (3)	C11A—C12A—H132	104 (3)
C11B—C13B—H134	109 (3)	H133—C12A—H132	111 (4)
H136—C13B—H134	107 (4)	C11A—C12A—H131	106 (2)
C11B—C13B—H135	114 (3)	H133—C12A—H131	113 (4)
H136—C13B—H135	117 (4)	H132—C12A—H131	112 (4)

C5B—C4B—C9B—C8B	1.1 (4)	O2A—C1A—C2A—C4A	−95.9 (4)
C2B—C4B—C9B—C8B	−179.3 (3)	O1A—C1A—C2A—C4A	81.7 (4)
C8B—C7B—C6B—C5B	1.4 (4)	O2A—C1A—C2A—C3A	29.6 (5)
C10B—C7B—C6B—C5B	−177.7 (3)	O1A—C1A—C2A—C3A	−152.8 (3)
C4B—C9B—C8B—C7B	0.5 (4)	C1A—C2A—C4A—C9A	85.5 (4)
C6B—C7B—C8B—C9B	−1.7 (4)	C3A—C2A—C4A—C9A	−38.7 (4)
C10B—C7B—C8B—C9B	177.3 (3)	C1A—C2A—C4A—C5A	−91.4 (4)
C9B—C4B—C2B—C1B	−84.3 (3)	C3A—C2A—C4A—C5A	144.4 (4)
C5B—C4B—C2B—C1B	95.3 (3)	C9A—C4A—C5A—C6A	1.2 (5)
C9B—C4B—C2B—C3B	151.2 (3)	C2A—C4A—C5A—C6A	178.3 (3)
C5B—C4B—C2B—C3B	−29.1 (4)	C4A—C5A—C6A—C7A	−0.5 (6)
C7B—C6B—C5B—C4B	0.2 (5)	C5A—C6A—C7A—C8A	−0.4 (5)
C9B—C4B—C5B—C6B	−1.4 (4)	C5A—C6A—C7A—C10A	177.0 (3)
C2B—C4B—C5B—C6B	178.9 (3)	C6A—C7A—C8A—C9A	0.5 (5)
C8B—C7B—C10B—C11B	−101.8 (3)	C10A—C7A—C8A—C9A	−176.8 (3)
C6B—C7B—C10B—C11B	77.2 (4)	C7A—C8A—C9A—C4A	0.2 (5)
C7B—C10B—C11B—C12B	68.0 (5)	C5A—C4A—C9A—C8A	−1.1 (5)
C7B—C10B—C11B—C13B	−168.3 (4)	C2A—C4A—C9A—C8A	−178.1 (3)
C4B—C2B—C1B—O2B	94.6 (3)	C8A—C7A—C10A—C11A	93.2 (5)
C3B—C2B—C1B—O2B	−139.2 (3)	C6A—C7A—C10A—C11A	−84.0 (5)
C4B—C2B—C1B—O1B	−83.5 (3)	C7A—C10A—C11A—C13A	−67.9 (5)
C3B—C2B—C1B—O1B	42.7 (4)	C7A—C10A—C11A—C12A	168.7 (4)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1B—H1BO···O2A	1.07 (5)	1.58 (5)	2.634 (4)	168 (4)
O1A—H1AO···O2B	0.94 (5)	1.73 (6)	2.651 (4)	169 (5)

Experimental details

Crystal data
Chemical formula	C₁₃H₁₈O₂
M_r	206.27
Crystal system, space group	Monoclinic, P2₁
Temperature (K)	298
a, b, c (Å)	12.456 (4), 8.0362 (11), 13.533 (3)
β (°)	112.86 (2)
V (Å³)	1248.2 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.07
Crystal size (mm)	0.40 × 0.40 × 0.30

Data collection
Diffractometer	Enraf-Nonius CAD-4 diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	3086, 2910, 1683
R_int	0.019
(sin θ/λ)_max (Å⁻¹)	0.638

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.105, 0.98
No. of reflections	2910
No. of parameters	416
No. of restraints	1
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.12, −0.11

Computer programs: CAD-4-PC Software (Enraf–Nonius, 1992), CELDIM in CAD-4-PC Software, XCAD4 (McArdle & Higgins, 1995), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEX (McArdle, 1995), OSCAIL (Version 9; McArdle, 1993).

Hydrogen-bond geometry (Å, °) in the crystal structures of the title compound and of its racemate top

D—H···A	D—H	H···A	D···A	D—H···A
O1A—H1AO···O2B	0.94 (5)	1.73 (6)	2.651 (4)	169 (5)
O1B—H1BO···O2A	1.07 (5)	1.58 (5)	2.634 (4)	168 (4)
O2—H2O···O1^i,a	0.963 (13)	1.664 (10)	2.627 (7)	179.5 (7)

Symmetry code: (i) 1 − x, 1 − y, 1 − z. Reference: (a) Freer et al. (1993).

Geometrical and conformational parameters (Å, °) of (S)- and racemic IBP top

	(S)-IBP	(S)-IBP	racemic IBP
	A	B
C5—C4—C2—C3	144.4 (4)	-29.1 (4)	140.9 (4)
C7—C10—C11—C12	-67.9 (5)	68.0 (5)	-67.3 (4)
C4—C2—C1—O2	81.7 (4)	-83.5 (3)	88.7 (3)
O1—C1	1.219 (3)	1.226 (3)	1.222 (3)
O2—C1	1.302 (4)	1.302 (4)	1.305 (3)
C1—C2	1.496 (5)	1.518 (4)	1.509 (3)

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