N-(4-Chloro­phenyl­sulfon­yl)-2-methyl­propanamide

Nirmala, P.G.; Foro, S.; Gowda, B.T.

doi:10.1107/S1600536811031394

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 67| Part 9| September 2011| Page o2274

doi:10.1107/S1600536811031394

Open

access

N-(4-Chlorophenylsulfonyl)-2-methylpropanamide

P. G. Nirmala,^a Sabine Foro ^b and B. Thimme Gowda ^a ^*

^aDepartment of Chemistry, Mangalore University, Mangalagangotri 574 199, Mangalore, India, and ^bInstitute of Materials Science, Darmstadt University of Technology, Petersenstrasse 23, D-64287 Darmstadt, Germany
^*Correspondence e-mail: gowdabt@yahoo.com

(Received 26 July 2011; accepted 3 August 2011; online 6 August 2011)

In the crystal structure of the title compound, C₁₀H₁₂ClNO₃S, the N—C bond in the C—SO₂—NH—C segment has a gauche torsion with respect to the S=O bonds. The molecule is twisted at the S atom with a C—S—N—C torsion angle of −62.3 (3)°. The benzene ring and the SO₂—NH—CO—C segment form a dihedral angle of 89.3 (1)°. In the crystal, molecules are linked by pairs of N—H⋯O hydrogen bonds into inversion dimers.

Related literature

For the sulfanilamide moiety in sulfonamide drugs, see: Maren (1976 ). For its ability to form hydrogen bonds in the solid state, see: Yang & Guillory (1972 ). For hydrogen-bonding modes of sulfonamides, see: Adsmond & Grant (2001 ). For our studies on the effects of substituents on the structures and other aspects of N-(aryl)-amides, see: Arjunan et al. (2004 ), on N-(aryl)-methanesulfonamides, see: Gowda et al. (2007 ), on N-(aryl)-arylsulfonamides, see: Gowda et al. (2003 ) and on N-(arylsulfonyl)-amides, see: Gowda et al. (2008 ); Shakuntala et al. (2011 ).

Experimental

Crystal data

C₁₀H₁₂ClNO₃S
M_r = 261.72
Triclinic, $[P \overline 1]$
a = 6.207 (1) Å
b = 10.395 (3) Å
c = 10.497 (3) Å
α = 70.150 (2)°
β = 79.160 (2)°
γ = 86.010 (2)°
V = 625.7 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.46 mm⁻¹
T = 293 K
0.46 × 0.20 × 0.08 mm

Data collection

Oxford Diffraction Xcalibur diffractometer with a Sapphire CCD detector
Absorption correction: multi-scan CrysAlis RED (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Yarnton, England.]$ ) T_min = 0.815, T_max = 0.964
3846 measured reflections
2476 independent reflections
1842 reflections with I > 2σ(I)
R_int = 0.014

Refinement

R[F² > 2σ(F²)] = 0.060
wR(F²) = 0.126
S = 1.19
2476 reflections
148 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.31 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1N⋯O1ⁱ	0.84 (2)	2.08 (2)	2.912 (4)	169 (3)
Symmetry code: (i) -x, -y+1, -z+2.

Data collection: CrysAlis CCD (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Yarnton, England.]$ ); cell refinement: CrysAlis RED (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Yarnton, England.]$ ); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811031394/nc2243sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811031394/nc2243Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811031394/nc2243Isup3.cml

checkCIF report

Comment top

The molecular structures of sulfonamide drugs contain the sulfanilamide moiety (Maren, 1976). The propensity for hydrogen bonding in the solid state, due to the presence of various hydrogen bond donors and acceptors gives rise to polymorphism (Yang & Guillory, 1972). The hydrogen bonding preferences of sulfonamides has also been studied (Adsmond & Grant, 2001). The nature and position of substituents play a significant role on the crystal structures of this class of compounds. As part of our work on the effects of substituents on the structures and other aspects of N-(aryl)-amides (Arjunan et al., 2004), N-(aryl)-methanesulfonamides (Gowda et al., 2007), N-(aryl)-arylsulfonamides (Gowda et al., 2003) and N-(arylsulfonyl)-acetamides (Gowda et al., 2008, Shakuntala et al., 2011), in the present work, the crystal structure of N-(4-chlorophenylsulfonyl)-2,2-dimethylacetamide (I) has been determined. The N—C bond in the C—SO₂—NH—C segment has gauche torsion with respect to the S═O bonds. The molecule is twisted at the S-atom with a C—S—N—C torsion angle of -62.3 (3)°, compared to the values of -72.5 (2)° in N-(4-chlorophenylsulfonyl)-2,2-dichloroacetamide (II) (Gowda et al., 2008) and N-(2-chlorophenylsulfonyl)- 2,2-dimethylacetamide (III)(Shakuntala et al., 2011).

Further, the dihedral angle between the benzene ring and the SO₂—NH—CO—C segment in (I) is 89.3 (1)°, compared to the values of 79.7 (1)° in (II) and 87.4 (1)° in (III).

In the crystal structure, the moleucles are connected into centrosymmetrically dimers by intermolecular N–H···O hydrogen bonding (Table 1). Part of the crystal structure is shown in Fig. 2.

Related literature top

For the sulfanilamide moiety in sulfonamide drugs, see: Maren (1976). For its ability to form hydrogen bonds in the solid state, see: Yang & Guillory (1972). For hydrogen-bonding modes of sulfonamides, see: Adsmond & Grant (2001). For our studies on the effects of substituents on the structures and other aspects of N-(aryl)-amides, see: Arjunan et al. (2004), on N-(aryl)-methanesulfonamides, see: Gowda et al. (2007), on N-(aryl)-arylsulfonamides, see: Gowda et al. (2003) and on N-(arylsulfonyl)-amides, see: Gowda et al. (2008); Shakuntala et al. (2011).

Experimental top

The title compound was prepared by refluxing 4-chlorobenzenesulfonamide (0.10 mole) with an excess of 2,2-dimethylacetyl chloride (0.20 mole) for about an hour on a water bath. The reaction mixture was cooled and poured into ice cold water. The resulting solid was separated, washed thoroughly with water and dissolved in warm dilute sodium hydrogen carbonate solution. The title compound was reprecipitated by acidifying the filtered solution with glacial acetic acid. It was filtered, dried and recrystallized from ethanol. The purity of the compound was checked by determining its melting point. It was further characterized by recording its infrared spectra.

Plate like colorless single crystals of the title compound used in X-ray diffraction studies were obtained from a slow evaporation of an ethanolic solution of the compound.

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2009); cell refinement: CrysAlis RED (Oxford Diffraction, 2009); data reduction: CrysAlis RED (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. Molecular structure of the title compound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. Crystal structure of the title compound showing the dimers. Hydrogen bonds are shown as dashed lines.

N-(4-Chlorophenylsulfonyl)-2-methylpropanamide top

Crystal data top

C₁₀H₁₂ClNO₃S	Z = 2
M_r = 261.72	F(000) = 272
Triclinic, P1	D_x = 1.389 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.207 (1) Å	Cell parameters from 1240 reflections
b = 10.395 (3) Å	θ = 3.3–27.8°
c = 10.497 (3) Å	µ = 0.46 mm⁻¹
α = 70.150 (2)°	T = 293 K
β = 79.160 (2)°	Plate, colourless
γ = 86.010 (2)°	0.46 × 0.20 × 0.08 mm
V = 625.7 (3) Å³

Data collection top

Oxford Diffraction Xcalibur diffractometer with a Sapphire CCD detector	2476 independent reflections
Radiation source: fine-focus sealed tube	1842 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.014
Rotation method data acquisition using ω and ϕ scans	θ_max = 26.4°, θ_min = 3.3°
Absorption correction: multi-scan CrysAlis RED (Oxford Diffraction, 2009)	h = −7→7
T_min = 0.815, T_max = 0.964	k = −12→12
3846 measured reflections	l = −13→13

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)] = 0.060	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.126	H atoms treated by a mixture of independent and constrained refinement
S = 1.19	w = 1/[σ²(F_o²) + (0.0233P)² + 0.632P] where P = (F_o² + 2F_c²)/3
2476 reflections	(Δ/σ)_max = 0.001
148 parameters	Δρ_max = 0.28 e Å⁻³
1 restraint	Δρ_min = −0.31 e Å⁻³

Crystal data top

C₁₀H₁₂ClNO₃S	γ = 86.010 (2)°
M_r = 261.72	V = 625.7 (3) Å³
Triclinic, P1	Z = 2
a = 6.207 (1) Å	Mo Kα radiation
b = 10.395 (3) Å	µ = 0.46 mm⁻¹
c = 10.497 (3) Å	T = 293 K
α = 70.150 (2)°	0.46 × 0.20 × 0.08 mm
β = 79.160 (2)°

Data collection top

Oxford Diffraction Xcalibur diffractometer with a Sapphire CCD detector	2476 independent reflections
Absorption correction: multi-scan CrysAlis RED (Oxford Diffraction, 2009)	1842 reflections with I > 2σ(I)
T_min = 0.815, T_max = 0.964	R_int = 0.014
3846 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.060	1 restraint
wR(F²) = 0.126	H atoms treated by a mixture of independent and constrained refinement
S = 1.19	Δρ_max = 0.28 e Å⁻³
2476 reflections	Δρ_min = −0.31 e Å⁻³
148 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	U_iso*/U_eq
C1	0.1905 (5)	0.2375 (3)	0.9043 (3)	0.0475 (7)
C2	−0.0001 (6)	0.2717 (4)	0.8506 (4)	0.0610 (9)
H2	−0.0818	0.3477	0.8593	0.073*
C3	−0.0683 (6)	0.1930 (4)	0.7844 (4)	0.0670 (10)
H3	−0.1957	0.2156	0.7468	0.080*
C4	0.0535 (7)	0.0805 (3)	0.7742 (4)	0.0638 (10)
C5	0.2423 (7)	0.0456 (4)	0.8278 (4)	0.0709 (11)
H5	0.3221	−0.0315	0.8207	0.085*
C6	0.3124 (6)	0.1255 (3)	0.8920 (4)	0.0612 (9)
H6	0.4421	0.1040	0.9271	0.073*
C7	0.4540 (6)	0.5278 (4)	0.7543 (4)	0.0578 (9)
C8	0.4194 (7)	0.6715 (4)	0.6608 (4)	0.0716 (11)
H8	0.3561	0.7263	0.7187	0.086*
C9	0.2542 (9)	0.6652 (6)	0.5756 (5)	0.1190 (19)
H9A	0.1202	0.6271	0.6350	0.143*
H9B	0.3103	0.6089	0.5208	0.143*
H9C	0.2265	0.7558	0.5165	0.143*
C10	0.6291 (10)	0.7353 (6)	0.5780 (6)	0.151 (3)
H10A	0.6959	0.6822	0.5219	0.182*
H10B	0.7258	0.7386	0.6383	0.182*
H10C	0.6015	0.8265	0.5202	0.182*
N1	0.3069 (5)	0.4914 (3)	0.8767 (3)	0.0560 (7)
H1N	0.200 (4)	0.541 (3)	0.892 (4)	0.067*
O1	0.0960 (4)	0.3525 (3)	1.0924 (2)	0.0729 (7)
O2	0.4794 (4)	0.2850 (3)	1.0314 (3)	0.0714 (7)
O3	0.5885 (4)	0.4482 (3)	0.7273 (3)	0.0863 (9)
Cl1	−0.0354 (3)	−0.01843 (12)	0.69033 (14)	0.1076 (5)
S1	0.27563 (15)	0.33738 (9)	0.99054 (9)	0.0559 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0524 (18)	0.0386 (16)	0.0429 (17)	0.0085 (14)	−0.0084 (14)	−0.0043 (13)
C2	0.055 (2)	0.056 (2)	0.074 (2)	0.0148 (16)	−0.0162 (18)	−0.0244 (18)
C3	0.063 (2)	0.063 (2)	0.072 (2)	0.0024 (18)	−0.0210 (19)	−0.014 (2)
C4	0.090 (3)	0.0428 (19)	0.053 (2)	−0.0118 (18)	−0.0140 (19)	−0.0066 (16)
C5	0.095 (3)	0.0419 (19)	0.077 (3)	0.0201 (19)	−0.026 (2)	−0.0180 (18)
C6	0.068 (2)	0.0471 (19)	0.070 (2)	0.0184 (17)	−0.0255 (19)	−0.0175 (17)
C7	0.052 (2)	0.059 (2)	0.059 (2)	0.0048 (17)	−0.0146 (17)	−0.0148 (17)
C8	0.086 (3)	0.062 (2)	0.057 (2)	0.007 (2)	−0.012 (2)	−0.0084 (18)
C9	0.146 (5)	0.114 (4)	0.095 (4)	0.039 (4)	−0.060 (4)	−0.020 (3)
C10	0.123 (5)	0.128 (5)	0.133 (5)	−0.026 (4)	−0.001 (4)	0.041 (4)
N1	0.0637 (19)	0.0447 (16)	0.0567 (17)	0.0105 (13)	−0.0102 (15)	−0.0155 (13)
O1	0.0929 (19)	0.0657 (16)	0.0489 (14)	0.0221 (14)	−0.0029 (13)	−0.0142 (12)
O2	0.0769 (17)	0.0681 (16)	0.0755 (17)	0.0171 (13)	−0.0381 (14)	−0.0221 (13)
O3	0.0719 (18)	0.087 (2)	0.0815 (19)	0.0296 (15)	−0.0026 (15)	−0.0156 (16)
Cl1	0.1677 (13)	0.0641 (7)	0.1053 (9)	−0.0180 (7)	−0.0502 (9)	−0.0294 (6)
S1	0.0676 (6)	0.0489 (5)	0.0494 (5)	0.0139 (4)	−0.0159 (4)	−0.0140 (4)

Geometric parameters (Å, º) top

C1—C6	1.374 (4)	C7—C8	1.510 (5)
C1—C2	1.378 (4)	C8—C10	1.481 (6)
C1—S1	1.753 (3)	C8—C9	1.500 (6)
C2—C3	1.370 (5)	C8—H8	0.9800
C2—H2	0.9300	C9—H9A	0.9600
C3—C4	1.372 (5)	C9—H9B	0.9600
C3—H3	0.9300	C9—H9C	0.9600
C4—C5	1.368 (5)	C10—H10A	0.9600
C4—Cl1	1.736 (4)	C10—H10B	0.9600
C5—C6	1.368 (5)	C10—H10C	0.9600
C5—H5	0.9300	N1—S1	1.639 (3)
C6—H6	0.9300	N1—H1N	0.840 (18)
C7—O3	1.199 (4)	O1—S1	1.433 (2)
C7—N1	1.380 (4)	O2—S1	1.425 (2)

C6—C1—C2	120.7 (3)	C10—C8—H8	107.9
C6—C1—S1	119.9 (3)	C9—C8—H8	107.9
C2—C1—S1	119.4 (2)	C7—C8—H8	107.9
C3—C2—C1	119.5 (3)	C8—C9—H9A	109.5
C3—C2—H2	120.2	C8—C9—H9B	109.5
C1—C2—H2	120.2	H9A—C9—H9B	109.5
C2—C3—C4	119.2 (3)	C8—C9—H9C	109.5
C2—C3—H3	120.4	H9A—C9—H9C	109.5
C4—C3—H3	120.4	H9B—C9—H9C	109.5
C5—C4—C3	121.5 (3)	C8—C10—H10A	109.5
C5—C4—Cl1	119.8 (3)	C8—C10—H10B	109.5
C3—C4—Cl1	118.7 (3)	H10A—C10—H10B	109.5
C6—C5—C4	119.2 (3)	C8—C10—H10C	109.5
C6—C5—H5	120.4	H10A—C10—H10C	109.5
C4—C5—H5	120.4	H10B—C10—H10C	109.5
C5—C6—C1	119.8 (3)	C7—N1—S1	125.8 (2)
C5—C6—H6	120.1	C7—N1—H1N	122 (3)
C1—C6—H6	120.1	S1—N1—H1N	110 (3)
O3—C7—N1	121.2 (3)	O2—S1—O1	119.07 (16)
O3—C7—C8	125.4 (3)	O2—S1—N1	110.56 (16)
N1—C7—C8	113.3 (3)	O1—S1—N1	103.75 (15)
C10—C8—C9	113.5 (4)	O2—S1—C1	108.79 (15)
C10—C8—C7	111.6 (4)	O1—S1—C1	108.78 (17)
C9—C8—C7	107.7 (4)	N1—S1—C1	104.95 (15)

C6—C1—C2—C3	0.0 (5)	N1—C7—C8—C9	−87.3 (4)
S1—C1—C2—C3	−179.3 (3)	O3—C7—N1—S1	−7.0 (5)
C1—C2—C3—C4	0.7 (6)	C8—C7—N1—S1	170.6 (3)
C2—C3—C4—C5	−0.5 (6)	C7—N1—S1—O2	54.8 (3)
C2—C3—C4—Cl1	179.9 (3)	C7—N1—S1—O1	−176.4 (3)
C3—C4—C5—C6	−0.6 (6)	C7—N1—S1—C1	−62.3 (3)
Cl1—C4—C5—C6	179.1 (3)	C6—C1—S1—O2	2.9 (3)
C4—C5—C6—C1	1.4 (6)	C2—C1—S1—O2	−177.8 (3)
C2—C1—C6—C5	−1.1 (5)	C6—C1—S1—O1	−128.3 (3)
S1—C1—C6—C5	178.3 (3)	C2—C1—S1—O1	51.1 (3)
O3—C7—C8—C10	−35.0 (6)	C6—C1—S1—N1	121.2 (3)
N1—C7—C8—C10	147.5 (4)	C2—C1—S1—N1	−59.4 (3)
O3—C7—C8—C9	90.2 (5)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···O1ⁱ	0.84 (2)	2.08 (2)	2.912 (4)	169 (3)

Symmetry code: (i) −x, −y+1, −z+2.

Experimental details

Crystal data
Chemical formula	C₁₀H₁₂ClNO₃S
M_r	261.72
Crystal system, space group	Triclinic, P1
Temperature (K)	293
a, b, c (Å)	6.207 (1), 10.395 (3), 10.497 (3)
α, β, γ (°)	70.150 (2), 79.160 (2), 86.010 (2)
V (Å³)	625.7 (3)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.46
Crystal size (mm)	0.46 × 0.20 × 0.08

Data collection
Diffractometer	Oxford Diffraction Xcalibur diffractometer with a Sapphire CCD detector
Absorption correction	Multi-scan CrysAlis RED (Oxford Diffraction, 2009)
T_min, T_max	0.815, 0.964
No. of measured, independent and observed [I > 2σ(I)] reflections	3846, 2476, 1842
R_int	0.014
(sin θ/λ)_max (Å⁻¹)	0.625

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.060, 0.126, 1.19
No. of reflections	2476
No. of parameters	148
No. of restraints	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.28, −0.31

Computer programs: CrysAlis CCD (Oxford Diffraction, 2009), CrysAlis RED (Oxford Diffraction, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···O1ⁱ	0.840 (18)	2.083 (19)	2.912 (4)	169 (3)

Symmetry code: (i) −x, −y+1, −z+2.

Acknowledgements

BTG thanks the University Grants Commission, Government of India, New Delhi, for a one time grant under its BSR scheme.

References

Adsmond, D. A. & Grant, D. J. W. (2001). J. Pharm. Sci. 90, 2058–2077. Web of Science CrossRef PubMed CAS Google Scholar
Arjunan, V., Mohan, S., Subramanian, S. & Gowda, B. T. (2004). Spectrochim. Acta Part A, 60, 1141–1159. CrossRef CAS Google Scholar
Gowda, B. T., Foro, S. & Fuess, H. (2007). Acta Cryst. E63, o2337. Web of Science CSD CrossRef IUCr Journals Google Scholar
Gowda, B. T., Foro, S., Nirmala, P. G., Sowmya, B. P. & Fuess, H. (2008). Acta Cryst. E64, o1521. CSD CrossRef IUCr Journals Google Scholar
Gowda, B. T., Jyothi, K., Kožíšek, J. & Fuess, H. (2003). Z. Naturforsch. Teil A, 58, 656–660. CAS Google Scholar
Maren, T. H. (1976). Annu. Rev. Pharmacol Toxicol. 16, 309–327. CrossRef CAS PubMed Web of Science Google Scholar
Oxford Diffraction (2009). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Yarnton, England. Google Scholar
Shakuntala, K., Foro, S. & Gowda, B. T. (2011). Acta Cryst. E67, o595. CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Yang, S. S. & Guillory, J. K. (1972). J. Pharm. Sci. 61, 26–40. CrossRef CAS PubMed Web of Science Google Scholar