4,4′-(Hexane-1,6-diyldi­oxy)dianiline

Khan, M.S.U.; Akhter, Z.; Bolte, M.; Siraj, A.; Siddiqi, H.M.

doi:10.1107/S160053680901321X

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 65| Part 5| May 2009| Page o1096

doi:10.1107/S160053680901321X

Open

access

4,4′-(Hexane-1,6-diyldioxy)dianiline

Muhammad Saif Ullah Khan,^a Zareen Akhter,^a ^* Michael Bolte,^b Amna Siraj ^a and Humaira M. Siddiqi ^a

^aDepartment of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan, and ^bInstitut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany
^*Correspondence e-mail: zareenakhter@yahoo.com

(Received 4 April 2009; accepted 7 April 2009; online 22 April 2009)

The complete molecule of the title compound, C₁₈H₂₄N₂O₂, is generated by a crystallographic inversion centre. The torsion angles in the hexamethylene chain are consistent with an antiperiplanar conformation, whereas the conformation of the O—CH₂—CH₂—CH₂ unit is gauche. The three-dimensional crystal packing is stabilized by N—H⋯O and N—H⋯N hydrogen bonding.

Related literature

For aromatic diamines as building blocks for the preparation of high-performance polymers, see: Mehdipour-Ataei (2005 ; Mehdipour-Ataei et al. (2007 ). For the use of flexible linkages, see: Shao et al. (2007 ); Yin et al. (1998 ).

Experimental

Crystal data

C₁₈H₂₄N₂O₂
M_r = 300.39
Orthorhombic, P b c a
a = 5.4777 (6) Å
b = 13.6049 (12) Å
c = 21.7278 (18) Å
V = 1619.2 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 173 K
0.33 × 0.23 × 0.11 mm

Data collection

Stoe IPDS-II two-circle diffractometer
Absorption correction: none
9301 measured reflections
1854 independent reflections
1403 reflections with I > 2σ(I)
R_int = 0.056

Refinement

R[F² > 2σ(F²)] = 0.039
wR(F²) = 0.103
S = 1.02
1854 reflections
109 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.18 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯N1ⁱ	0.939 (18)	2.318 (18)	3.2248 (11)	162.1 (13)
N1—H1B⋯O1ⁱⁱ	0.899 (16)	2.318 (16)	3.1724 (14)	158.6 (13)
Symmetry codes: (i) $[x+{\script{1\over 2}}, y, -z+{\script{3\over 2}}]$ ; (ii) $[-x+{\script{3\over 2}}, y+{\script{1\over 2}}, z]$ .

Data collection: X-AREA (Stoe & Cie, 2001 ); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009 ) and XP (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053680901321X/tk2416sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S160053680901321X/tk2416Isup2.hkl

checkCIF report

Comment top

Aromatic diamines are valuable building blocks for the preparation of high-performance polymers including polyamides, polyimides and polyureas (Mehdipour-Ataei, 2005). Therefore, these can be used to produce desired alterations in the chemical nature of macromolecular chains (Mehdipour-Ataei et al., 2007). Much research in recent years has focused on the design and synthesis of novel diamines in order to obtain suitable polymers. One of the popular approaches to achieve this goal is the introduction of flexible linkages such as an ether moiety (Shao et al., 2007) and/or methylene spacers (Yin et al., 1998) in the core structure of the diamines. These linkages increase the degree of freedom by reducing the segmental rotational barrier and inhibit close chain packing. The title compound, (I), in which flexible methylene spacers are present between the aryl ether moieties, is an outcome of efforts to modify the aromatic diamine monomers by flexible linkages in order to improve the processability and performance of the resulting polymers.

Molecules of (I) (Fig. 1) are located about a crystallographic centre of inversion. All torsion angles in the hexamethylene chain indicate an antiperiplanar conformation whereas the conformation of the O—CH₂—CH₂—CH₂ unit is gauche. The crystal packing (Table 1) is stabilized by N—H···O and N—H···N hydrogen bonds which lead to a three-dimensional network.

Related literature top

For aromatic diamines as building blocks for the preparation of

high-performance polymers, see: Mehdipour-Ataei (2005; Mehdipour-Ataei et al. (2007). For the use of flexible linkages, see: Shao et al. (2007); Yin et al. (1998).

Experimental top

The title compound (I) was synthesized in two steps. In the first step, bis(4-nitrophenoxy)hexane was prepared by Williamson's reaction. A three-neck round bottom flask equipped with Dean-Stark trap, thermometer, magnetic stirrer and nitrogen inlet was charged with a suspension of 1,6-hexane diol (2.25 g; 19.1 mmol) and anhydrous potassium carbonate (5.3 g; 38.2 mmol) in a mixture of N,N'-dimethyl formamide (DMF) (60 ml) and toluene (20 ml), and refluxed (at 403–408 K) for 2 h for azeotropic removal of water. After cooling to 343–343 K, 1-fluoro-4-nitro benzene (4.05 ml; 38.2 mmol) was added and the mixture was again refluxed for 6 h. Subsequently, some toluene was distilled off and the resulting mixture was poured into 500 ml of chilled water after cooling to room temperature. The crude product was filtered as yellow solid, washed thoroughly with water and recrystallized from ethanol to afford bis(4-nitrophenoxy)hexane. In the second step, a two-neck flask was charged with 1,6-bis(4-nitrophenoxy)hexane (2.5 g; 6.94 mmol), hydrazine monohydrate (10 ml), ethanol (80 ml) and 0.1 g of 5% palladium on carbon (Pd–C). The mixture was refluxed for 18 h and then filtered to remove the Pd–C. The filtrate was concentrated on rotary evaporator to remove the solvent and the resulting crude solid was recrystallized from ethanol to afford colourless crystals suitable for X-ray analysis, which were stored in air-tight glass bottles for further studies. Yield 72%; m.p. 414 K. Elemental analysis. Found C, 72.03, H, 7.90, N, 9.25. Calculated for C₁₈H₂₄N₂O₂: C, 71.97, H, 8.05, N, 9.33; IR (KBr pellet) in cm^-1: 3395, 3311 (NH₂), 1632 (N-H bending), 1385 (C-N stretching), 1233 (C-O-C), 2935 (C—H aliphatic), 3219 (C—H aromatic). ¹H NMR (CDCl₃) δ: 3.92 (s, 4H, NH₂), 6.40 (d, 4H, J = 3.0 Hz), 6.70 (d, 4H, J = 2.9 Hz), 3.88 (t, 4H), 1.78 (m, 4H), 1.51 (m, 4H) p.p.m. ¹³C NMR (CDCl₃) δ: 147.52 (2 C, C4), 139.83 (2 C, C1), 116.42 (4 C, C2,2'), 115.67 (4 C, C3,3'), 68.54 (2 C, C5), 29.38 (2 C, C6), 25.91 (2 C, C7) p.p.m.

Computing details top

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA (Stoe & Cie, 2001); data reduction: X-AREA (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009) and XP (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

Fig. 1. Perspective view of (I) showing the atom labelling scheme and displacement ellipsoids at the 50% probability level. H atoms are drawn as spheres of arbitrary radii. Unlabelled atoms are related by the symmetry operator 1 - x, -y, 1 - z.

4,4'-(Hexane-1,6-diyldioxy)dianiline top

Crystal data top

C₁₈H₂₄N₂O₂	F(000) = 648
M_r = 300.39	D_x = 1.232 Mg m⁻³
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 6791 reflections
a = 5.4777 (6) Å	θ = 3.6–27.7°
b = 13.6049 (12) Å	µ = 0.08 mm⁻¹
c = 21.7278 (18) Å	T = 173 K
V = 1619.2 (3) Å³	Plate, colourless
Z = 4	0.33 × 0.23 × 0.11 mm

Data collection top

Stoe IPDS-II two-circle diffractometer	1403 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.056
Graphite monochromator	θ_max = 27.6°, θ_min = 3.5°
ω scans	h = −7→5
9301 measured reflections	k = −17→17
1854 independent reflections	l = −24→28

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	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.103	w = 1/[σ²(F_o²) + (0.0626P)²] where P = (F_o² + 2F_c²)/3
S = 1.02	(Δ/σ)_max = 0.001
1854 reflections	Δρ_max = 0.24 e Å⁻³
109 parameters	Δρ_min = −0.18 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.016 (2)

Crystal data top

C₁₈H₂₄N₂O₂	V = 1619.2 (3) Å³
M_r = 300.39	Z = 4
Orthorhombic, Pbca	Mo Kα radiation
a = 5.4777 (6) Å	µ = 0.08 mm⁻¹
b = 13.6049 (12) Å	T = 173 K
c = 21.7278 (18) Å	0.33 × 0.23 × 0.11 mm

Data collection top

Stoe IPDS-II two-circle diffractometer	1403 reflections with I > 2σ(I)
9301 measured reflections	R_int = 0.056
1854 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.039	0 restraints
wR(F²) = 0.103	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	Δρ_max = 0.24 e Å⁻³
1854 reflections	Δρ_min = −0.18 e Å⁻³
109 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
N1	0.9705 (2)	0.55262 (7)	0.71082 (5)	0.0289 (3)
H1A	1.131 (3)	0.5464 (11)	0.7257 (7)	0.045 (4)*
H1B	0.956 (3)	0.6080 (11)	0.6885 (7)	0.044 (4)*
O1	0.60683 (17)	0.20721 (5)	0.60327 (4)	0.0303 (2)
C1	0.8839 (2)	0.46681 (8)	0.68123 (5)	0.0235 (3)
C2	0.6800 (2)	0.47129 (8)	0.64298 (5)	0.0258 (3)
H2	0.6060	0.5332	0.6351	0.031*
C3	0.5818 (2)	0.38691 (8)	0.61598 (5)	0.0255 (3)
H3	0.4432	0.3917	0.5899	0.031*
C4	0.6879 (2)	0.29578 (8)	0.62748 (5)	0.0237 (3)
C5	0.8897 (2)	0.29005 (8)	0.66663 (5)	0.0262 (3)
H5	0.9604	0.2279	0.6755	0.031*
C6	0.9879 (2)	0.37456 (8)	0.69278 (5)	0.0259 (3)
H6	1.1270	0.3697	0.7187	0.031*
C7	0.3984 (2)	0.20972 (8)	0.56312 (5)	0.0269 (3)
H7A	0.4363	0.2478	0.5255	0.032*
H7B	0.2582	0.2410	0.5841	0.032*
C8	0.3376 (2)	0.10382 (8)	0.54656 (5)	0.0267 (3)
H8A	0.1770	0.1024	0.5257	0.032*
H8B	0.3227	0.0652	0.5850	0.032*
C9	0.5262 (2)	0.05471 (7)	0.50505 (5)	0.0248 (3)
H9A	0.6900	0.0621	0.5237	0.030*
H9B	0.5282	0.0885	0.4647	0.030*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0355 (7)	0.0239 (5)	0.0274 (5)	−0.0043 (4)	−0.0043 (5)	−0.0005 (4)
O1	0.0369 (6)	0.0204 (4)	0.0336 (5)	−0.0005 (3)	−0.0102 (4)	−0.0031 (3)
C1	0.0284 (6)	0.0230 (5)	0.0192 (5)	−0.0030 (4)	0.0032 (5)	−0.0002 (4)
C2	0.0311 (7)	0.0213 (5)	0.0251 (6)	0.0025 (5)	−0.0006 (5)	0.0002 (4)
C3	0.0271 (6)	0.0256 (6)	0.0238 (5)	0.0003 (4)	−0.0023 (5)	0.0001 (4)
C4	0.0277 (7)	0.0209 (5)	0.0226 (5)	−0.0018 (4)	0.0012 (5)	−0.0021 (4)
C5	0.0295 (7)	0.0222 (5)	0.0269 (6)	0.0036 (4)	0.0000 (5)	0.0001 (4)
C6	0.0249 (6)	0.0287 (6)	0.0241 (5)	0.0004 (5)	−0.0025 (5)	0.0000 (4)
C7	0.0283 (7)	0.0248 (6)	0.0275 (6)	0.0012 (5)	−0.0018 (5)	−0.0031 (4)
C8	0.0277 (7)	0.0253 (6)	0.0271 (6)	−0.0030 (4)	0.0004 (5)	−0.0025 (4)
C9	0.0259 (6)	0.0234 (6)	0.0250 (5)	−0.0041 (4)	−0.0005 (5)	−0.0015 (4)

Geometric parameters (Å, º) top

N1—C1	1.4147 (14)	C5—C6	1.3908 (16)
N1—H1A	0.939 (18)	C5—H5	0.9500
N1—H1B	0.899 (16)	C6—H6	0.9500
O1—C4	1.3879 (13)	C7—C8	1.5218 (15)
O1—C7	1.4372 (15)	C7—H7A	0.9900
C1—C2	1.3937 (17)	C7—H7B	0.9900
C1—C6	1.4011 (15)	C8—C9	1.5258 (16)
C2—C3	1.3968 (15)	C8—H8A	0.9900
C2—H2	0.9500	C8—H8B	0.9900
C3—C4	1.3919 (16)	C9—C9ⁱ	1.532 (2)
C3—H3	0.9500	C9—H9A	0.9900
C4—C5	1.3966 (17)	C9—H9B	0.9900

C1—N1—H1A	113.3 (10)	C5—C6—H6	119.7
C1—N1—H1B	114.7 (10)	C1—C6—H6	119.7
H1A—N1—H1B	110.0 (14)	O1—C7—C8	107.15 (9)
C4—O1—C7	117.63 (8)	O1—C7—H7A	110.3
C2—C1—C6	118.16 (10)	C8—C7—H7A	110.3
C2—C1—N1	120.25 (10)	O1—C7—H7B	110.3
C6—C1—N1	121.43 (11)	C8—C7—H7B	110.3
C1—C2—C3	121.54 (10)	H7A—C7—H7B	108.5
C1—C2—H2	119.2	C7—C8—C9	113.96 (10)
C3—C2—H2	119.2	C7—C8—H8A	108.8
C4—C3—C2	119.72 (11)	C9—C8—H8A	108.8
C4—C3—H3	120.1	C7—C8—H8B	108.8
C2—C3—H3	120.1	C9—C8—H8B	108.8
O1—C4—C3	124.86 (11)	H8A—C8—H8B	107.7
O1—C4—C5	115.83 (9)	C8—C9—C9ⁱ	112.53 (12)
C3—C4—C5	119.31 (10)	C8—C9—H9A	109.1
C6—C5—C4	120.58 (10)	C9ⁱ—C9—H9A	109.1
C6—C5—H5	119.7	C8—C9—H9B	109.1
C4—C5—H5	119.7	C9ⁱ—C9—H9B	109.1
C5—C6—C1	120.67 (11)	H9A—C9—H9B	107.8

C6—C1—C2—C3	−0.75 (17)	C3—C4—C5—C6	−1.58 (18)
N1—C1—C2—C3	−176.24 (11)	C4—C5—C6—C1	1.14 (18)
C1—C2—C3—C4	0.31 (18)	C2—C1—C6—C5	0.03 (17)
C7—O1—C4—C3	0.28 (17)	N1—C1—C6—C5	175.46 (10)
C7—O1—C4—C5	179.52 (10)	C4—O1—C7—C8	−176.37 (9)
C2—C3—C4—O1	−179.93 (11)	O1—C7—C8—C9	−69.25 (12)
C2—C3—C4—C5	0.85 (17)	C7—C8—C9—C9ⁱ	173.85 (12)
O1—C4—C5—C6	179.13 (10)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···N1ⁱⁱ	0.939 (18)	2.318 (18)	3.2248 (11)	162.1 (13)
N1—H1B···O1ⁱⁱⁱ	0.899 (16)	2.318 (16)	3.1724 (14)	158.6 (13)

Symmetry codes: (ii) x+1/2, y, −z+3/2; (iii) −x+3/2, y+1/2, z.

Experimental details

Crystal data
Chemical formula	C₁₈H₂₄N₂O₂
M_r	300.39
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	173
a, b, c (Å)	5.4777 (6), 13.6049 (12), 21.7278 (18)
V (Å³)	1619.2 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.08
Crystal size (mm)	0.33 × 0.23 × 0.11

Data collection
Diffractometer	Stoe IPDS-II two-circle diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	9301, 1854, 1403
R_int	0.056
(sin θ/λ)_max (Å⁻¹)	0.652

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.103, 1.02
No. of reflections	1854
No. of parameters	109
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.24, −0.18

Computer programs: X-AREA (Stoe & Cie, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009) and XP (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···N1ⁱ	0.939 (18)	2.318 (18)	3.2248 (11)	162.1 (13)
N1—H1B···O1ⁱⁱ	0.899 (16)	2.318 (16)	3.1724 (14)	158.6 (13)

Symmetry codes: (i) x+1/2, y, −z+3/2; (ii) −x+3/2, y+1/2, z.

Acknowledgements

The authors are grateful to the Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan, and the Institute for Inorganic Chemistry, University of Frankfurt, Germany, for providing laboratory and analytical facilities.

References

Mehdipour-Ataei, S. (2005). Eur. Polym. J. 41, 65–71. Web of Science CrossRef CAS Google Scholar
Mehdipour-Ataei, S., Tadjarodi, A. & Babanzadeh, S. (2007). Eur. Polym. J. 43, 498–506. Web of Science CrossRef CAS Google Scholar
Shao, Y., Li, Y., Zhao, X., Ma, T., Gong, C. & Yang, F. (2007). Eur. Polym. J. 43, 4389–4397. Web of Science CrossRef CAS 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
Stoe & Cie (2001). X-AREA. Stoe & Cie, Darmstadt, Germany. Google Scholar
Yin, J., Ye, Y. F. & Wang, Z. G. (1998). Eur. Polym. J. 34, 1839–1843. Web of Science CrossRef CAS Google Scholar