Crystal structure of 6-eth­oxy­pyridin-1-ium-2-olate

Luo, K.; Guo, Q.; Wang, Y.; Luo, D.

doi:10.1107/S1600536814020224

organic compounds

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Volume 70| Part 11| November 2014| Page o1146

doi:10.1107/S1600536814020224

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Crystal structure of 6-ethoxypyridin-1-ium-2-olate

Kaijun Luo,^a ^* Qing Guo,^a Yan Wang ^a and Daibing Luo ^b

^aCollege of Chemistry and Materials Science, Sichuan Normal University, Chengdu, Sichuan 610068, People's Republic of China, and ^bAnalytical and Testing Center, Sichuan University, Chengdu, Sichuan 610065, People's Republic of China
^*Correspondence e-mail: luodaibing690312@163.com

Edited by O. Blacque, University of Zürich, Switzerland (Received 5 August 2014; accepted 9 September 2014; online 4 October 2014)

In the title compound, C₇H₉NO₂, all non-H atoms are essentially coplanar [r.m.s. deviation = 0.032 Å]. The largest deviation from the plane of the pyridine ring is 0.105 (6) Å for the terminal C atom of the ethoxy group. In the crystal, molecules are linked by pairs of N—H⋯O hydrogen bonds, forming inversion dimers. These dimers are further linked by C—H⋯π interactions and weak π–π interactions between pyridine rings [centroid–centroid distance = 4.023 (1) Å].

Keywords: crystal structure; 6-ethoxypyridin-1-ium-2-olate; zwitterion; hydrogen bonding; C—H⋯π interactions.

CCDC reference: 1023404

1. Related literature

For general background to 2-iodo-5-hydroxypyridine derivatives and their applications, see: Cho et al. (2003 ); Hegmann et al. (2003 ); Savelon et al. (1998 ); Wang et al. (2012 ). For the synthesis of the title compound, see: Hutchinson et al. (2001 ); Seton et al. (2001 ).

2. Experimental

2.1. Crystal data

C₇H₉NO₂
M_r = 139.15
Monoclinic, P 2₁ /n
a = 8.3037 (11) Å
b = 7.0999 (6) Å
c = 12.0767 (15) Å
β = 93.402 (13)°
V = 710.74 (14) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 293 K
0.3 × 0.3 × 0.2 mm

2.2. Data collection

Agilent Xcalibur Eos diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2011 ) T_min = 0.606, T_max = 1.000
2957 measured reflections
1452 independent reflections
949 reflections with I > 2σ(I)
R_int = 0.018

2.3. Refinement

R[F² > 2σ(F²)] = 0.055
wR(F²) = 0.150
S = 1.09
1452 reflections
96 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.33 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

Cg is the centroid of the N1,C1–C5 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O1ⁱ	0.87 (2)	1.90 (2)	2.762 (2)	174 (2)
C7—H7A⋯Cgⁱⁱ	0.96	2.90	3.792 (3)	155
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) $[-x+{\script{3\over 2}}, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Data collection: CrysAlis PRO (Agilent, 2011); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: OLEX2 (Dolomanov et al., 2009 ); software used to prepare material for publication: OLEX2.

Supporting information

CCDC reference: 1023404

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536814020224/zq2227sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536814020224/zq2227Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536814020224/zq2227Isup3.txt

Supporting information file. DOI: 10.1107/S1600536814020224/zq2227Isup4.cml

checkCIF report

Comment top

2-iodo-5-Hydroxypyridine derivatives are important materials for medicinal chemistry and material science. Recently, during the preparation of 2-iodo-5-hydroxypyridine, we accidentally got the 2-hydroxy-6-ethoxypyridine by-product, which is easy to sublimate to form the corresponding pyridinium by transferring hydrogen proton of 2-hydroxy to pyridine nitrogen atom. 2-hydroxy-6-ethoxypyridine can be obtained in a two-step synthesis from 2-iodo-5-nitropyridine.

In the title compound, C₇H₉NO₂, all non-H atoms are essentially coplanar. The mean deviation for all non-hydrogen atoms of the molecule is 0.0315 Å, and the largest deviation from the least-squares plane of the six non-H atoms of the pyridine ring is 0.105 (6) Å for the terminal C atom of the ethoxy group. In the crystal, inversion-related molecules are linked through N1—H1···O1ⁱ hydrogen bonds forming dimers [symmetry operators (i): -x+1, -y+1, -z+1]. These dimers are further linked by C—H···π interactions [H···centroid distance = 2.90 Å, C—H···centroid = 155°] between H7A and one pyridine ring [symmetry operator: -x+3/2, y-1/2, -z+1/2] and weak π–π interactions between pyridine rings [centroid–centroid distance = 4.023 (1) Å).

Related literature top

For general background to 2-iodo-5-hydroxypyridine derivatives and their applications, see: Cho et al. (2003); Hegmann et al. (2003); Savelon et al. (1998); Wang et al. (2012). For the synthesis of the title compound, see: Hutchinson et al. (2001); Seton et al. (2001).

Experimental top

A mixture of 2-iodo-5-nitropyridine (0.2 g, 0.8 mmol), SnCl₂.2(H₂O) (0.904 g, 4 mmol) and 25 ml ethanol was refluxed under inert atmosphere for 5 h. The mixture was evaporated to remove the solvent and the residue was extracted with ethyl acetate and H₂O, and the organic layer was washed with 10% aqueous NaOH and H₂O and dried over anhydrous MgSO₄. The crude product was purified by flash chromatography [silica gel, petroleum ether: ethyl acetate (5:1)]. A light yellow solid (yield: 24%) of 2-ethoxy-5-aminopyridine was obtained. A solution of 2-ethoxy-5-aminopyridine (0.2 g, 0.90 mmol) and 40% fluoroboric acid (2 ml) was cooled down to 5 °C, then a 25% sodium nitrite solution (1.0 ml) was added. After stirring for 2 h at 5 °C, Cu₂O (0.08 g, 0.54 mmol) and 30% hydrous CuNO₃ (25 ml) were added to the solution and the mixture was stirred for 5 h at room temperature. The mixture was adjusted to pH 7 by 20% hydrous K₂CO₃ and filtered. The filtrate was extracted by ethyl acetate, the organic layer was washed with water and dried over MgSO₄. The solvent was evaporated and the solid production was chromatographed on a silica gel column [petroleum ether: ethyl acetate (2:1). A white solid (yield: 18%), 2-hydroxy-6-ethoxypyridine, was obtained. Furthermore, single crystals of ¨the title compound were obtained by sublimation. ¹H NMR (DMSO, 400 MHz) δ: 10.62 (s, 1 H), 748 (t, J = 8 Hz, 1 H), 6.12 (t, J = 8 Hz, 2 H), 4.18 (d, J = 8 Hz, 2 H), 1.26 (t, J = 8 Hz, 3 H).

Computing details top

Data collection: CrysAlis PRO (Agilent, 2011); cell refinement: CrysAlis PRO (Agilent, 2011); data reduction: CrysAlis PRO (Agilent, 2011); program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Figures top

The molecular structure of the title complex, with non-hydrogen atoms labels and 50% probability displacement ellipsoids.

Packing of the title compound viewed along the b direction.

6-Ethoxypyridin-1-ium-2-olate top

Crystal data top

C₇H₉NO₂	F(000) = 296
M_r = 139.15	D_x = 1.300 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 809 reflections
a = 8.3037 (11) Å	θ = 3.8–24.3°
b = 7.0999 (6) Å	µ = 0.10 mm⁻¹
c = 12.0767 (15) Å	T = 293 K
β = 93.402 (13)°	Block, white
V = 710.74 (14) Å³	0.3 × 0.3 × 0.2 mm
Z = 4

Data collection top

Agilent Xcalibur Eos diffractometer	1452 independent reflections
Radiation source: Enhance (Mo) X-ray Source	949 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.018
Detector resolution: 16.0874 pixels mm^-1	θ_max = 26.4°, θ_min = 3.1°
ω scans	h = −9→10
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2011)	k = −5→8
T_min = 0.606, T_max = 1.000	l = −7→15
2957 measured reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F² > 2σ(F²)] = 0.055	w = 1/[σ²(F_o²) + (0.0675P)² + 0.0301P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.150	(Δ/σ)_max = 0.001
S = 1.09	Δρ_max = 0.24 e Å⁻³
1452 reflections	Δρ_min = −0.33 e Å⁻³
96 parameters

Crystal data top

C₇H₉NO₂	V = 710.74 (14) Å³
M_r = 139.15	Z = 4
Monoclinic, P2₁/n	Mo Kα radiation
a = 8.3037 (11) Å	µ = 0.10 mm⁻¹
b = 7.0999 (6) Å	T = 293 K
c = 12.0767 (15) Å	0.3 × 0.3 × 0.2 mm
β = 93.402 (13)°

Data collection top

Agilent Xcalibur Eos diffractometer	1452 independent reflections
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2011)	949 reflections with I > 2σ(I)
T_min = 0.606, T_max = 1.000	R_int = 0.018
2957 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.055	0 restraints
wR(F²) = 0.150	H atoms treated by a mixture of independent and constrained refinement
S = 1.09	Δρ_max = 0.24 e Å⁻³
1452 reflections	Δρ_min = −0.33 e Å⁻³
96 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. Reflections were merged by SHELXL according to the crystal class for the calculation of statistics and refinement.

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

	x	y	z	U_iso*/U_eq
C1	0.6392 (2)	0.3124 (3)	0.59009 (17)	0.0554 (5)
C2	0.7456 (3)	0.1850 (3)	0.64769 (19)	0.0642 (6)
H2	0.7774	0.2064	0.7218	0.077*
C3	0.8004 (3)	0.0333 (3)	0.5951 (2)	0.0688 (7)
H3	0.8694	−0.0493	0.6344	0.083*
C4	0.7581 (3)	−0.0052 (3)	0.4841 (2)	0.0663 (7)
H4	0.7979	−0.1108	0.4492	0.080*
C5	0.6563 (2)	0.1176 (2)	0.42860 (18)	0.0521 (5)
C6	0.6502 (3)	−0.0472 (3)	0.2572 (2)	0.0683 (7)
H6A	0.6240	−0.1649	0.2928	0.082*
H6B	0.7658	−0.0431	0.2495	0.082*
C7	0.5627 (3)	−0.0328 (4)	0.1469 (2)	0.0824 (8)
H7A	0.5910	−0.1376	0.1017	0.124*
H7B	0.5919	0.0825	0.1117	0.124*
H7C	0.4486	−0.0338	0.1557	0.124*
N1	0.60093 (19)	0.2701 (2)	0.48106 (14)	0.0507 (5)
H1	0.538 (3)	0.350 (3)	0.445 (2)	0.082 (8)*
O1	0.58033 (19)	0.4567 (2)	0.63138 (12)	0.0762 (5)
O2	0.60054 (17)	0.11012 (17)	0.32261 (12)	0.0629 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0558 (12)	0.0567 (11)	0.0530 (12)	−0.0021 (9)	−0.0032 (10)	0.0008 (10)
C2	0.0651 (14)	0.0644 (12)	0.0619 (14)	0.0015 (10)	−0.0066 (11)	0.0103 (11)
C3	0.0624 (14)	0.0641 (13)	0.0792 (17)	0.0075 (11)	−0.0027 (12)	0.0185 (12)
C4	0.0646 (14)	0.0521 (11)	0.0828 (18)	0.0098 (10)	0.0096 (13)	0.0026 (11)
C5	0.0504 (11)	0.0462 (10)	0.0603 (13)	−0.0039 (8)	0.0081 (10)	−0.0007 (9)
C6	0.0732 (15)	0.0593 (12)	0.0738 (16)	0.0059 (10)	0.0173 (13)	−0.0164 (11)
C7	0.0939 (19)	0.0759 (15)	0.0782 (18)	0.0062 (13)	0.0121 (15)	−0.0260 (13)
N1	0.0508 (10)	0.0472 (9)	0.0536 (10)	0.0040 (7)	0.0000 (8)	−0.0025 (8)
O1	0.0997 (13)	0.0716 (10)	0.0550 (10)	0.0237 (9)	−0.0148 (9)	−0.0131 (7)
O2	0.0732 (10)	0.0531 (8)	0.0628 (10)	0.0086 (6)	0.0059 (8)	−0.0118 (7)

Geometric parameters (Å, º) top

C1—C2	1.418 (3)	C5—O2	1.336 (2)
C1—N1	1.369 (2)	C6—H6A	0.9700
C1—O1	1.251 (2)	C6—H6B	0.9700
C2—H2	0.9300	C6—C7	1.483 (3)
C2—C3	1.344 (3)	C6—O2	1.442 (2)
C3—H3	0.9300	C7—H7A	0.9600
C3—C4	1.392 (3)	C7—H7B	0.9600
C4—H4	0.9300	C7—H7C	0.9600
C4—C5	1.363 (3)	N1—H1	0.87 (3)
C5—N1	1.349 (2)

N1—C1—C2	115.75 (19)	C7—C6—H6A	110.2
O1—C1—C2	125.0 (2)	C7—C6—H6B	110.2
O1—C1—N1	119.25 (17)	O2—C6—H6A	110.2
C1—C2—H2	120.1	O2—C6—H6B	110.2
C3—C2—C1	119.9 (2)	O2—C6—C7	107.33 (18)
C3—C2—H2	120.1	C6—C7—H7A	109.5
C2—C3—H3	118.7	C6—C7—H7B	109.5
C2—C3—C4	122.6 (2)	C6—C7—H7C	109.5
C4—C3—H3	118.7	H7A—C7—H7B	109.5
C3—C4—H4	121.3	H7A—C7—H7C	109.5
C5—C4—C3	117.5 (2)	H7B—C7—H7C	109.5
C5—C4—H4	121.3	C1—N1—H1	116.0 (17)
N1—C5—C4	120.1 (2)	C5—N1—C1	124.13 (18)
O2—C5—C4	127.98 (19)	C5—N1—H1	119.9 (17)
O2—C5—N1	111.91 (17)	C5—O2—C6	117.46 (16)
H6A—C6—H6B	108.5

C1—C2—C3—C4	0.5 (3)	C7—C6—O2—C5	175.32 (18)
C2—C1—N1—C5	0.8 (3)	N1—C1—C2—C3	−0.7 (3)
C2—C3—C4—C5	−0.3 (3)	N1—C5—O2—C6	−179.67 (16)
C3—C4—C5—N1	0.3 (3)	O1—C1—C2—C3	179.4 (2)
C3—C4—C5—O2	179.6 (2)	O1—C1—N1—C5	−179.39 (18)
C4—C5—N1—C1	−0.6 (3)	O2—C5—N1—C1	−179.95 (16)
C4—C5—O2—C6	1.0 (3)

Hydrogen-bond geometry (Å, º) top

Cg is the centroid of the N1,C1–C5 ring.

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1ⁱ	0.87 (2)	1.90 (2)	2.762 (2)	174 (2)
C7—H7A···Cgⁱⁱ	0.96	2.90	3.792 (3)	155

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

Hydrogen-bond geometry (Å, º) top

Cg is the centroid of the N1,C1–C5 ring.

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1ⁱ	0.87 (2)	1.90 (2)	2.762 (2)	174 (2)
C7—H7A···Cgⁱⁱ	0.96	2.90	3.792 (3)	155

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

Acknowledgements

Support from the National Natural Science Foundation of China (grant Nos. 21072141 and 21172161) is gratefully acknowledged.

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CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 70| Part 11| November 2014| Page o1146

doi:10.1107/S1600536814020224

Open

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