Crystal structure of (E)-dodec-2-enoic acid

Sonneck, M.; Peppel, T.; Spannenberg, A.; Wohlrab, S.

doi:10.1107/S2056989015011937

organic compounds

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ISSN: 2056-9890

Volume 71| Part 7| July 2015| Pages o528-o529

doi:10.1107/S2056989015011937

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Crystal structure of (E)-dodec-2-enoic acid

Marcel Sonneck,^a Tim Peppel,^a ^* Anke Spannenberg ^a and Sebastian Wohlrab ^a

^aLeibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059 Rostock, Germany
^*Correspondence e-mail: tim.peppel@catalysis.de

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 20 June 2015; accepted 22 June 2015; online 30 June 2015)

The crystal structure of (E)-dodec-2-enoic acid, C₁₂H₂₂O₂, an α,β-unsaturated carboxylic acid with a melting point (295 K) near room temperature, is characterized by carboxylic acid inversion dimers linked by pairs of O—H⋯O hydrogen bonds. The carboxylic acid group and the following three carbon atoms of the chain of the (E)-dodec-2-enoic acid molecule lie almost in one plane (r.m.s. deviation for the four C atoms and two O atoms = 0.012 Å), whereas the remaining carbon atoms of the hydrocarbon chain adopt a nearly fully staggered conformation [moduli of torsion angles vary from 174.01 (13) to 179.97 (13)°].

Keywords: crystal structure; hydrogen bonding; dimer; unsaturated carboxylic acid; fatty acid.

CCDC reference: 1407997

1. Related literature

For the synthesis of unsaturated α,β-carboxylic acids including the title compound by adapted routes established by Knoevenagel (1898 ) and Doebner (1902 ), see: Shabtai et al. (1981 ). For crystal structure determinations of related α,β-unsaturated carboxylic acids, see, for acrylic acid: Higgs et al. (1963 ), Chatani et al. (1963 ), Boese et al. (1999 ), or Oswald et al. (2011 ); see, for crotonic acid: Shimizu et al. (1974 ); see, for (E)-pent-2-enoic acid: Peppel et al. (2015a ); see, for (E)-hex-2-enoic acid: Peppel et al. (2015b ); see, for (E)-undecen-2-enoic acid: Sonneck et al. (2015 ). For structures of co-crystals containing (E)-hex-2-enoic acid, see: Aakeröy et al. (2003 ), or Stanton & Bak (2008 ).

2. Experimental

2.1. Crystal data

C₁₂H₂₂O₂
M_r = 198.29
Triclinic, $[P \overline 1]$
a = 4.6475 (2) Å
b = 5.4169 (2) Å
c = 24.7041 (10) Å
α = 91.547 (2)°
β = 91.788 (2)°
γ = 102.3158 (19)°
V = 606.96 (4) Å³
Z = 2
Cu Kα radiation
μ = 0.56 mm⁻¹
T = 150 K
0.44 × 0.30 × 0.12 mm

2.2. Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2014 ) T_min = 0.80, T_max = 0.94
12048 measured reflections
2117 independent reflections
1964 reflections with I > 2σ(I)
R_int = 0.026

2.3. Refinement

R[F² > 2σ(F²)] = 0.046
wR(F²) = 0.131
S = 1.13
2117 reflections
129 parameters
H-atom parameters constrained
Δρ_max = 0.29 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O2ⁱ	0.84	1.80	2.6319 (15)	170
Symmetry code: (i) -x+1, -y+3, -z.

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2013 ); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015 ); molecular graphics: SHELXL2014/7; software used to prepare material for publication: SHELXL2014/7.

Supporting information

CCDC reference: 1407997

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: 10.1107/S2056989015011937/hb7452sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S2056989015011937/hb7452Isup2.hkl

Supporting information file. DOI: 10.1107/S2056989015011937/hb7452Isup3.cml

checkCIF report

Synthesis and crystallization top

Malonic acid (25.0 g, 240.2 mmol, 1.0 eq) is dissolved in dry pyridine (38.0 g, 480.5 mmol, 2.0 eq) at room temperature in a three-necked flask equipped with a magnetic stir bar and a reflux condenser under a mild flow of argon. Decanal (37.5 g, 240.2 mmol, 1.0 eq) is then added in one portion and the resulting clear solution is further stirred for 72 h at room temperature under argon. Afterwards, the resulting light yellow to orange solution is brought to an acidic pH value by adding phosphoric acid at 0 °C (42.5wt. %, 138.5 g, 600.6 mmol, 2.5 eq). The resulting two layers are extracted three times with 150 mL portions of ethyl acetate and reduced to a volume of ca. 150 mL in vacuo. To remove impurities from aldol condensation the raw acid is converted into the corresponding sodium salt by addition of an aqueous solution of sodium carbonate (20.4 g, 192.2 mmol, 0.8 eq in 200 mL). After stirring for 30 minutes the water phase is separated and extracted three times with 150 mL portions of ethyl acetate. The water phase is then acidified with concentrated hydrochloric acid (37.0wt. %, 35.5 g, 360.4 mmol, 1.5 eq), the organic phase is separated and the water phase is again extracted three times with 150 mL portions of ethyl acetate. The combined organic phases are dried over Na₂SO₄ and evaporated to dryness under diminished pressure. The resulting raw product is further purified by distillation in vacuo yielding the product in purity >99% (GC). M. p. 22 °C. ¹H NMR (400 MHz, CDCl₃): δ = 12.15 (br s, 1H, OH); 7.09 (dt, ³J = 15.6 Hz, ³J = 7.0 Hz, 1H, -CH-); 5.82 (dt, ³J = 15.6 Hz, ⁴J = 1.6 Hz, 1H, -CH-); 2.26-2.19 (m, 2H, -CH₂-); 1.50-1.42 (m, 2H, -CH₂-); 1.32-1.24 (m, 12H, 6x -CH₂-); 0.90-0.86 (m, 3H, -CH₃-). ¹³C NMR (100 MHz, CDCl₃): δ = 172.53 (CO); 152.68 (CH); 120.76 (CH); 32.47 (CH₂); 32.02 (CH₂); 29.61 (CH₂), 29.52 (CH₂), 29.43 (CH₂); 29.29 (CH₂); 28.02 (CH₂); 22.81 (CH₂); 14.23 (CH₃). MS (EI, 70eV): m/z = 198 (M⁺, 0), 99 (16), 98 (12), 97 (17), 96 (14), 95 (11), 86 (17), 84 (18), 83 (16), 82 (12), 81 (20), 73 (34), 71 (13), 70 (15), 69 (21), 68 (18), 67 (20), 57 (29), 56 (22), 55 (47), 54 (11), 53 (20), 45 (14), 43 (70), 42 (19), 41 (100), 40 (14), 39 (52), 29 (58). HRMS (ESI-TOF/MS): calculated for C₁₂H₂₂O₂ ([M—H]^-) 197.1547, found 197.15481. Elemental analysis for C₁₂H₂₂O₂ % (calc.): C 72.53 (72.68); H 11.24 (11.18). Suitable single crystals were grown by slow evaporation of an ethanolic solution at -30 °C over one week.

Refinement top

H atoms were placed in idealized positions with d(C—H) = 0.95 Å (CH), 0.99 Å (CH₂), 0.98 Å (CH₃) and refined using a riding model with U_iso(H) fixed at 1.2 U_eq(C) for CH and CH₂ and 1.5 U_eq(C) for CH₃. The carboxylic acid group was assigned by examining the C—O distances and H1 was placed using the AFIX 147 instruction (d(O—H) = 0.84 Å, U_iso(H) fixed at 1.5 U_eq(O)).

Related literature top

For the synthesis of unsaturated α,β-carboxylic acids including the title compound by adapted routes established by Knoevenagel (1898) and Doebner (1902), see: Shabtai et al. (1981). For crystal structure determinations of related α,β-unsaturated carboxylic acids, see, for acrylic acid: Higgs et al. (1963), Chatani et al. (1963), Boese et al. (1999), or Oswald et al. (2011); see, for crotonic acid: Shimizu et al. (1974); see, for (E)-pent-2-enoic acid: Peppel et al. (2015a); see, for (E)-hex-2-enoic acid: Peppel et al. (2015b); see, for (E)-undecen-2-enoic acid: Sonneck et al. (2015). For structures of co-crystals containing (E)-hex-2-enoic acid, see: Aakeröy et al. (2003), or Stanton & Bak (2008).

Computing details top

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: SHELXL2014/7 (Sheldrick, 2015); software used to prepare material for publication: SHELXL2014/7 (Sheldrick, 2015).

Figures top

	Fig. 1. Molecular structure of the title compound with atom labelling and displacement ellipsoids drawn at 50% probability level.
	Fig. 2. Packing diagram showing intermolecular hydrogen bonding.

(E)-dodec-2-enoic acid top

Crystal data top

C₁₂H₂₂O₂	Z = 2
M_r = 198.29	F(000) = 220
Triclinic, P1	D_x = 1.085 Mg m⁻³
a = 4.6475 (2) Å	Cu Kα radiation, λ = 1.54178 Å
b = 5.4169 (2) Å	Cell parameters from 6666 reflections
c = 24.7041 (10) Å	θ = 3.6–66.9°
α = 91.547 (2)°	µ = 0.56 mm⁻¹
β = 91.788 (2)°	T = 150 K
γ = 102.3158 (19)°	Plate, colourless
V = 606.96 (4) Å³	0.44 × 0.30 × 0.12 mm

Data collection top

Bruker APEXII CCD diffractometer	2117 independent reflections
Radiation source: microfocus	1964 reflections with I > 2σ(I)
Multilayer monochromator	R_int = 0.026
Detector resolution: 8.3333 pixels mm^-1	θ_max = 66.0°, θ_min = 3.6°
ϕ and ω scans	h = −5→5
Absorption correction: multi-scan (SADABS; Bruker, 2014)	k = −6→6
T_min = 0.80, T_max = 0.94	l = −29→29
12048 measured reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.046	H-atom parameters constrained
wR(F²) = 0.131	w = 1/[σ²(F_o²) + (0.0529P)² + 0.282P] where P = (F_o² + 2F_c²)/3
S = 1.13	(Δ/σ)_max < 0.001
2117 reflections	Δρ_max = 0.29 e Å⁻³
129 parameters	Δρ_min = −0.23 e Å⁻³

Crystal data top

C₁₂H₂₂O₂	γ = 102.3158 (19)°
M_r = 198.29	V = 606.96 (4) Å³
Triclinic, P1	Z = 2
a = 4.6475 (2) Å	Cu Kα radiation
b = 5.4169 (2) Å	µ = 0.56 mm⁻¹
c = 24.7041 (10) Å	T = 150 K
α = 91.547 (2)°	0.44 × 0.30 × 0.12 mm
β = 91.788 (2)°

Data collection top

Bruker APEXII CCD diffractometer	2117 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2014)	1964 reflections with I > 2σ(I)
T_min = 0.80, T_max = 0.94	R_int = 0.026
12048 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.046	0 restraints
wR(F²) = 0.131	H-atom parameters constrained
S = 1.13	Δρ_max = 0.29 e Å⁻³
2117 reflections	Δρ_min = −0.23 e Å⁻³
129 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.7187 (3)	1.2963 (3)	0.03952 (6)	0.0277 (4)
C2	0.8819 (3)	1.1356 (3)	0.06965 (6)	0.0314 (4)
H2	0.9763	1.0250	0.0497	0.038*
C3	0.9029 (3)	1.1384 (3)	0.12290 (6)	0.0306 (4)
H3	0.8092	1.2517	0.1421	0.037*
C4	1.0622 (4)	0.9777 (3)	0.15566 (7)	0.0332 (4)
H4A	1.2230	1.0881	0.1778	0.040*
H4B	1.1523	0.8714	0.1309	0.040*
C5	0.8573 (3)	0.8076 (3)	0.19299 (6)	0.0303 (4)
H5A	0.7510	0.9129	0.2148	0.036*
H5B	0.7090	0.6858	0.1706	0.036*
C6	1.0184 (3)	0.6615 (3)	0.23115 (6)	0.0304 (4)
H6A	1.1303	0.5606	0.2094	0.036*
H6B	1.1618	0.7832	0.2545	0.036*
C7	0.8121 (4)	0.4855 (3)	0.26692 (6)	0.0311 (4)
H7A	0.6701	0.3631	0.2435	0.037*
H7B	0.6985	0.5865	0.2882	0.037*
C8	0.9696 (4)	0.3400 (3)	0.30579 (6)	0.0313 (4)
H8A	1.0830	0.2386	0.2846	0.038*
H8B	1.1115	0.4622	0.3293	0.038*
C9	0.7607 (4)	0.1648 (3)	0.34138 (7)	0.0333 (4)
H9A	0.6186	0.0429	0.3178	0.040*
H9B	0.6474	0.2664	0.3626	0.040*
C10	0.9160 (4)	0.0181 (3)	0.38039 (7)	0.0341 (4)
H10A	1.0257	−0.0866	0.3592	0.041*
H10B	1.0612	0.1398	0.4035	0.041*
C11	0.7074 (4)	−0.1519 (4)	0.41657 (8)	0.0432 (4)
H11A	0.5556	−0.2675	0.3936	0.052*
H11B	0.6057	−0.0462	0.4393	0.052*
C12	0.8622 (5)	−0.3083 (4)	0.45332 (8)	0.0495 (5)
H12A	0.9605	−0.4159	0.4311	0.074*
H12B	0.7169	−0.4145	0.4755	0.074*
H12C	1.0089	−0.1952	0.4770	0.074*
O1	0.5999 (3)	1.4499 (2)	0.06736 (5)	0.0374 (3)
H1	0.5041	1.5251	0.0464	0.056*
O2	0.7029 (3)	1.2789 (2)	−0.01126 (4)	0.0363 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0262 (7)	0.0246 (8)	0.0319 (8)	0.0035 (6)	0.0022 (6)	0.0044 (6)
C2	0.0306 (8)	0.0301 (8)	0.0352 (9)	0.0100 (7)	0.0022 (6)	0.0046 (6)
C3	0.0274 (8)	0.0291 (8)	0.0358 (9)	0.0071 (6)	0.0010 (6)	0.0042 (6)
C4	0.0309 (8)	0.0359 (9)	0.0347 (9)	0.0110 (7)	−0.0009 (6)	0.0067 (7)
C5	0.0300 (8)	0.0306 (8)	0.0318 (8)	0.0104 (7)	−0.0016 (6)	0.0032 (6)
C6	0.0294 (8)	0.0295 (8)	0.0334 (8)	0.0095 (7)	−0.0032 (6)	0.0030 (6)
C7	0.0311 (8)	0.0301 (8)	0.0335 (8)	0.0102 (7)	−0.0021 (6)	0.0033 (6)
C8	0.0311 (8)	0.0301 (8)	0.0342 (8)	0.0098 (7)	−0.0023 (6)	0.0040 (7)
C9	0.0327 (8)	0.0335 (9)	0.0347 (9)	0.0096 (7)	−0.0019 (7)	0.0051 (7)
C10	0.0351 (9)	0.0342 (9)	0.0347 (9)	0.0109 (7)	−0.0010 (7)	0.0061 (7)
C11	0.0415 (10)	0.0459 (11)	0.0433 (10)	0.0103 (8)	0.0025 (8)	0.0147 (8)
C12	0.0554 (12)	0.0499 (11)	0.0450 (11)	0.0127 (9)	0.0035 (9)	0.0192 (9)
O1	0.0442 (7)	0.0364 (7)	0.0367 (6)	0.0193 (5)	0.0013 (5)	0.0060 (5)
O2	0.0453 (7)	0.0357 (7)	0.0307 (6)	0.0143 (5)	−0.0012 (5)	0.0053 (5)

Geometric parameters (Å, º) top

C1—O2	1.2543 (19)	C7—H7B	0.9900
C1—O1	1.2881 (19)	C8—C9	1.524 (2)
C1—C2	1.473 (2)	C8—H8A	0.9900
C2—C3	1.316 (2)	C8—H8B	0.9900
C2—H2	0.9500	C9—C10	1.524 (2)
C3—C4	1.496 (2)	C9—H9A	0.9900
C3—H3	0.9500	C9—H9B	0.9900
C4—C5	1.527 (2)	C10—C11	1.518 (2)
C4—H4A	0.9900	C10—H10A	0.9900
C4—H4B	0.9900	C10—H10B	0.9900
C5—C6	1.525 (2)	C11—C12	1.523 (2)
C5—H5A	0.9900	C11—H11A	0.9900
C5—H5B	0.9900	C11—H11B	0.9900
C6—C7	1.522 (2)	C12—H12A	0.9800
C6—H6A	0.9900	C12—H12B	0.9800
C6—H6B	0.9900	C12—H12C	0.9800
C7—C8	1.524 (2)	O1—H1	0.8400
C7—H7A	0.9900

O2—C1—O1	123.37 (14)	H7A—C7—H7B	107.7
O2—C1—C2	119.24 (14)	C9—C8—C7	113.34 (13)
O1—C1—C2	117.38 (13)	C9—C8—H8A	108.9
C3—C2—C1	122.91 (15)	C7—C8—H8A	108.9
C3—C2—H2	118.5	C9—C8—H8B	108.9
C1—C2—H2	118.5	C7—C8—H8B	108.9
C2—C3—C4	125.30 (15)	H8A—C8—H8B	107.7
C2—C3—H3	117.4	C8—C9—C10	113.76 (13)
C4—C3—H3	117.4	C8—C9—H9A	108.8
C3—C4—C5	112.03 (13)	C10—C9—H9A	108.8
C3—C4—H4A	109.2	C8—C9—H9B	108.8
C5—C4—H4A	109.2	C10—C9—H9B	108.8
C3—C4—H4B	109.2	H9A—C9—H9B	107.7
C5—C4—H4B	109.2	C11—C10—C9	113.50 (14)
H4A—C4—H4B	107.9	C11—C10—H10A	108.9
C6—C5—C4	113.32 (13)	C9—C10—H10A	108.9
C6—C5—H5A	108.9	C11—C10—H10B	108.9
C4—C5—H5A	108.9	C9—C10—H10B	108.9
C6—C5—H5B	108.9	H10A—C10—H10B	107.7
C4—C5—H5B	108.9	C10—C11—C12	113.18 (15)
H5A—C5—H5B	107.7	C10—C11—H11A	108.9
C7—C6—C5	113.10 (13)	C12—C11—H11A	108.9
C7—C6—H6A	109.0	C10—C11—H11B	108.9
C5—C6—H6A	109.0	C12—C11—H11B	108.9
C7—C6—H6B	109.0	H11A—C11—H11B	107.8
C5—C6—H6B	109.0	C11—C12—H12A	109.5
H6A—C6—H6B	107.8	C11—C12—H12B	109.5
C6—C7—C8	113.85 (13)	H12A—C12—H12B	109.5
C6—C7—H7A	108.8	C11—C12—H12C	109.5
C8—C7—H7A	108.8	H12A—C12—H12C	109.5
C6—C7—H7B	108.8	H12B—C12—H12C	109.5
C8—C7—H7B	108.8	C1—O1—H1	109.5

O2—C1—C2—C3	−178.37 (15)	C5—C6—C7—C8	−179.36 (13)
O1—C1—C2—C3	1.9 (2)	C6—C7—C8—C9	179.97 (13)
C1—C2—C3—C4	179.24 (14)	C7—C8—C9—C10	179.96 (13)
C2—C3—C4—C5	−120.08 (17)	C8—C9—C10—C11	178.76 (14)
C3—C4—C5—C6	−174.01 (13)	C9—C10—C11—C12	176.92 (15)
C4—C5—C6—C7	−178.05 (13)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2ⁱ	0.84	1.80	2.6319 (15)	170

Symmetry code: (i) −x+1, −y+3, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2ⁱ	0.84	1.80	2.6319 (15)	170

Symmetry code: (i) −x+1, −y+3, −z.

Acknowledgements

The authors thank P. Thiele (University of Rostock) for the DSC measurements and Professor Dr. J. G. de Vries (LIKAT) for helpful support.

References

Aakeröy, C. B., Beatty, A. M., Helfrich, B. A. & Nieuwenhuyzen, M. (2003). Cryst. Growth Des. 3, 159–165. Web of Science CSD CrossRef Google Scholar
Boese, R., Bläser, D., Steller, I., Latz, R. & Bäumen, A. (1999). Acta Cryst. C55 IUC9900006. Google Scholar
Bruker (2013). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker (2014). APEX2 and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Chatani, Y., Sakata, Y. & Nitta, I. (1963). J. Polym. Sci. B Polym. Lett. 1, 419–421. CrossRef Web of Science Google Scholar
Doebner, O. (1902). Ber. Dtsch. Chem. Ges. 35, 1136–1147. CrossRef CAS Google Scholar
Higgs, M. A. & Sass, R. L. (1963). Acta Cryst. 16, 657–661. CSD CrossRef IUCr Journals Web of Science Google Scholar
Knoevenagel, E. (1898). Ber. Dtsch. Chem. Ges. 31, 2596–2619. CrossRef CAS Google Scholar
Oswald, I. D. H. & Urquhart, A. J. (2011). CrystEngComm, 13, 4503–4507. Web of Science CSD CrossRef CAS Google Scholar
Peppel, T., Sonneck, M., Spannenberg, A. & Wohlrab, S. (2015a). Acta Cryst. E71, o316. CSD CrossRef IUCr Journals Google Scholar
Peppel, T., Sonneck, M., Spannenberg, A. & Wohlrab, S. (2015b). Acta Cryst. E71, o323. CSD CrossRef IUCr Journals Google Scholar
Shabtai, J., Ney-Igner, E. & Pines, H. (1981). J. Org. Chem. 46, 3795–3802. CrossRef CAS Web of Science Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Shimizu, S., Kekka, S., Kashino, S. & Haisa, M. (1974). Bull. Chem. Soc. Jpn, 47, 1627–1631. CrossRef CAS Web of Science Google Scholar
Sonneck, M., Peppel, T., Spannenberg, A. & Wohlrab, S. (2015). Acta Cryst. E71, o426–o427. CSD CrossRef IUCr Journals Google Scholar
Stanton, M. K. & Bak, A. (2008). Cryst. Growth Des. 8, 3856–3862. Web of Science CSD CrossRef CAS Google Scholar

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ISSN: 2056-9890

Volume 71| Part 7| July 2015| Pages o528-o529

doi:10.1107/S2056989015011937

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