Crystal structure of 2,6-dimethyl-4-pyridone hemihydrate

The title compound (systematic name: 2,6-dimethyl-1H-pyridin-4-one hemihydrate), C₇H₉NO·0.5H₂O, has a single planar mol­ecule in the asymmetric unit with the non-H atoms possessing a mean deviation from planarity of 0.021 Å. There is also half of a water mol­ecule present in the asymmetric unit. In the crystal, infinite (001) sheets are formed by N—H...O and O—H...O hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 120 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.030
• wR factor = 0.078
• Data-to-parameter ratio = 14.4

checkCIF/PLATON results

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Alert level C
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600          3 Report
PLAT913_ALERT_3_C Missing # of Very Strong Reflections in FCF ....          4 Note

Alert level G
PLAT002_ALERT_2_G Number of Distance or Angle Restraints on AtSite          4 Note
PLAT172_ALERT_4_G The CIF-Embedded .res File Contains DFIX Records          4 Report
PLAT860_ALERT_3_G Number of Least-Squares Restraints .............          3 Note
PLAT910_ALERT_3_G Missing # of FCF Reflection(s) Below Th(Min) ...          1 Report

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   2 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   4 ALERT level G = General information/check it is not something unexpected

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
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S1. Comment

The structure of the title compound shows that 2,6-di­methyl-4-hy­droxy­pyridine takes the pyridone form in the solid state. Though the title compound has not been crystallographically characterized, a structure of the molecule bound to zirconium has been reported (Castillo et al., 1987) with similar bond distances and angles observed. The parent 4-pyridone has been structurally characterized (Tyl et al., 2008) and exhibits similar chains linked by head-to-tail N–H···O hydrogen bonds, which are also observed in the close derivative Clopidol (Boer, 1972). While the title compound crystallizes in a 2:1 ratio of pyridone to water, the hydrate of the parent molecule crystallizes in a 5:6 ratio (Jones, 2001).

The molecular structure of the title compound is shown in Figure 1. The molecule is near planar with the non-hydrogen atoms possessing a mean deviation from the plane of 0.021 Å. Head-to-tail N1–H1···O1 hydrogen bonding leads to chains that are further linked by O2–H2···O1 hydrogen bonds with water molecules in the crystal to form two-dimensional (001) sheets. The packing of the title compound indicating hydrogen bonding is shown in Figure 2.

S2. Experimental

A commercial sample (Oakwood Chemical) of 4-hy­droxy­pyridine was used for the crystallization. Crystals suitable for single crystal X-ray analysis were grown by slow evaporation of a methanol solution.

S3. Refinement

All non-hydrogen atoms were refined anisotropically (XL) by full matrix least squares on F². Hydrogen atoms H1 and H2 were found from a Fourier difference map. H1 was refined at a fixed distance of 0.87 (0.005) Å and an isotropic displacement parameter 1.20 times U_eq of the parent N atom. H2 was refined at a fixed distance of 0.86 (0.005) Å and an isotropic displacement parameter 1.50 times U_eq of the parent O atom. The remaining hydrogen atoms were placed in calculated positions and then refined with riding models with C—H lengths of 0.98 Å for (CH₃) and 0.95 Å for (CH) with isotropic displacement parameters set to 1.20 times U_eq of the parent C atoms.

Related literature

For the crystal structure of the parent 4-pyridone, see: Jones (2001); Tyl et al. (2008). For the title compound bound to zirconium, see: Castillo et al. (1987). For the structure of a chloro-substituted variant of the title compound, see: Boer (1972).

Structure description

The structure of the title compound shows that 2,6-di­methyl-4-hy­droxy­pyridine takes the pyridone form in the solid state. Though the title compound has not been crystallographically characterized, a structure of the molecule bound to zirconium has been reported (Castillo et al., 1987) with similar bond distances and angles observed. The parent 4-pyridone has been structurally characterized (Tyl et al., 2008) and exhibits similar chains linked by head-to-tail N–H···O hydrogen bonds, which are also observed in the close derivative Clopidol (Boer, 1972). While the title compound crystallizes in a 2:1 ratio of pyridone to water, the hydrate of the parent molecule crystallizes in a 5:6 ratio (Jones, 2001).

The molecular structure of the title compound is shown in Figure 1. The molecule is near planar with the non-hydrogen atoms possessing a mean deviation from the plane of 0.021 Å. Head-to-tail N1–H1···O1 hydrogen bonding leads to chains that are further linked by O2–H2···O1 hydrogen bonds with water molecules in the crystal to form two-dimensional (001) sheets. The packing of the title compound indicating hydrogen bonding is shown in Figure 2.

A commercial sample (Oakwood Chemical) of 4-hy­droxy­pyridine was used for the crystallization. Crystals suitable for single crystal X-ray analysis were grown by slow evaporation of a methanol solution.

For the crystal structure of the parent 4-pyridone, see: Jones (2001); Tyl et al. (2008). For the title compound bound to zirconium, see: Castillo et al. (1987). For the structure of a chloro-substituted variant of the title compound, see: Boer (1972).

Refinement details

All non-hydrogen atoms were refined anisotropically (XL) by full matrix least squares on F². Hydrogen atoms H1 and H2 were found from a Fourier difference map. H1 was refined at a fixed distance of 0.87 (0.005) Å and an isotropic displacement parameter 1.20 times U_eq of the parent N atom. H2 was refined at a fixed distance of 0.86 (0.005) Å and an isotropic displacement parameter 1.50 times U_eq of the parent O atom. The remaining hydrogen atoms were placed in calculated positions and then refined with riding models with C—H lengths of 0.98 Å for (CH₃) and 0.95 Å for (CH) with isotropic displacement parameters set to 1.20 times U_eq of the parent C atoms.

Computing details

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009) and publCIF (Westrip, 2010).

Figures

	Fig. 1. Molecular structure of the title compound, showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are drawn as spheres of arbitrary radius.
	Fig. 2. Molecular packing of the title compound with hydrogen bonding shown as dashed lines.

2,6-Dimethyl-1H-pyridin-4-one hemihydrate

Crystal data

C7H9NO·0.5H2O	F(000) = 568
Mr = 132.16	Dx = 1.266 Mg m^−3
Orthorhombic, Aba2	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: A 2 -2ac	Cell parameters from 9829 reflections
a = 12.4859 (17) Å	θ = 7.1–72.4°
b = 14.3697 (19) Å	µ = 0.73 mm^−1
c = 7.732 (1) Å	T = 120 K
V = 1387.3 (3) Å^3	NEEDLE, colourless
Z = 8	0.5 × 0.1 × 0.1 mm

Data collection

Bruker Venture D8 CMOS diffractometer	1366 independent reflections
Radiation source: microfocus Cu	1352 reflections with I > 2σ(I)
HELIOS MX monochromator	Rint = 0.060
φ and ω scans	θmax = 72.4°, θmin = 7.1°
Absorption correction: multi-scan (SADABS; Bruker, 2014)	h = −15→15
Tmin = 0.554, Tmax = 0.754	k = −17→17
11786 measured reflections	l = −9→9

Refinement

Refinement on F^2	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F^2 > 2σ(F^2)] = 0.030	w = 1/[σ^2(Fo^2) + (0.0453P)^2 + 0.3383P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.078	(Δ/σ)max < 0.001
S = 1.09	Δρmax = 0.15 e Å^−3
1366 reflections	Δρmin = −0.19 e Å^−3
95 parameters	Absolute structure: Flack x determined using 611 quotients [(I^+)-(I^-)]/[(I^+)+(I^-)] (Parsons et al., 2013.
3 restraints	Absolute structure parameter: 0.05 (12)

Special details

Experimental. Absorption correction: SADABS-2014/4 (Bruker,2014) was used for absorption correction. wR2(int) was 0.1440 before and 0.0881 after correction. The Ratio of minimum to maximum transmission is 0.7350. The λ/2 correction factor is 0.00150.

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 (Ų)

	x	y	z	Uiso*/Ueq
O1	0.47723 (9)	0.33620 (8)	0.49203 (19)	0.0287 (3)
O2	0.5000	0.5000	0.6889 (3)	0.0399 (5)
N1	0.16883 (11)	0.24949 (11)	0.4446 (2)	0.0215 (3)
C3	0.35308 (14)	0.22232 (12)	0.3962 (2)	0.0234 (4)
H3	0.4083	0.1841	0.3504	0.028*
C2	0.24877 (14)	0.19343 (12)	0.3853 (2)	0.0222 (4)
C4	0.38007 (12)	0.30864 (12)	0.4748 (2)	0.0226 (4)
C7	0.09367 (14)	0.39066 (13)	0.5690 (3)	0.0265 (4)
H7A	0.0630	0.4210	0.4669	0.040*
H7B	0.1158	0.4381	0.6527	0.040*
H7C	0.0399	0.3499	0.6218	0.040*
C6	0.18900 (13)	0.33399 (11)	0.5164 (2)	0.0217 (4)
C1	0.21576 (15)	0.10115 (12)	0.3125 (3)	0.0270 (4)
H1A	0.1736	0.0672	0.3988	0.040*
H1B	0.2797	0.0650	0.2828	0.040*
H1C	0.1724	0.1109	0.2085	0.040*
C5	0.29237 (13)	0.36395 (12)	0.5339 (2)	0.0229 (4)
H5	0.3061	0.4226	0.5862	0.027*
H2	0.4956 (19)	0.4524 (12)	0.621 (3)	0.034*
H1	0.1043 (9)	0.2265 (14)	0.444 (4)	0.027*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0205 (5)	0.0250 (6)	0.0405 (8)	−0.0007 (5)	−0.0004 (6)	−0.0028 (6)
O2	0.0553 (14)	0.0318 (11)	0.0324 (11)	−0.0147 (10)	0.000	0.000
N1	0.0206 (6)	0.0206 (7)	0.0234 (7)	−0.0014 (5)	0.0004 (6)	0.0008 (6)
C3	0.0240 (8)	0.0215 (8)	0.0246 (8)	0.0035 (6)	0.0014 (7)	0.0012 (8)
C2	0.0268 (8)	0.0193 (8)	0.0205 (7)	0.0009 (6)	−0.0014 (7)	0.0022 (7)
C4	0.0229 (8)	0.0208 (8)	0.0241 (9)	0.0003 (6)	−0.0011 (7)	0.0038 (8)
C7	0.0245 (8)	0.0243 (8)	0.0309 (10)	0.0025 (7)	−0.0008 (7)	−0.0041 (8)
C6	0.0244 (8)	0.0196 (8)	0.0213 (8)	0.0009 (6)	−0.0012 (7)	0.0019 (7)
C1	0.0309 (9)	0.0216 (8)	0.0284 (10)	−0.0005 (7)	−0.0007 (8)	−0.0012 (8)
C5	0.0255 (8)	0.0174 (7)	0.0258 (8)	−0.0004 (6)	−0.0006 (7)	0.0004 (7)

Geometric parameters (Å, º)

O1—C4	1.283 (2)	C7—H7A	0.9800
O2—H2	0.862 (7)	C7—H7B	0.9800
N1—C2	1.362 (2)	C7—H7C	0.9800
N1—C6	1.359 (2)	C7—C6	1.498 (2)
N1—H1	0.871 (7)	C6—C5	1.367 (2)
C3—H3	0.9500	C1—H1A	0.9800
C3—C2	1.370 (2)	C1—H1B	0.9800
C3—C4	1.422 (3)	C1—H1C	0.9800
C2—C1	1.498 (2)	C5—H5	0.9500
C4—C5	1.428 (2)
C2—N1—H1	116.8 (15)	C6—C7—H7A	109.5
C6—N1—C2	122.02 (14)	C6—C7—H7B	109.5
C6—N1—H1	120.9 (16)	C6—C7—H7C	109.5
C2—C3—H3	119.5	N1—C6—C7	116.70 (14)
C2—C3—C4	121.06 (16)	N1—C6—C5	119.79 (15)
C4—C3—H3	119.5	C5—C6—C7	123.49 (16)
N1—C2—C3	119.80 (16)	C2—C1—H1A	109.5
N1—C2—C1	116.63 (15)	C2—C1—H1B	109.5
C3—C2—C1	123.57 (16)	C2—C1—H1C	109.5
O1—C4—C3	122.52 (15)	H1A—C1—H1B	109.5
O1—C4—C5	121.34 (16)	H1A—C1—H1C	109.5
C3—C4—C5	116.14 (15)	H1B—C1—H1C	109.5
H7A—C7—H7B	109.5	C4—C5—H5	119.4
H7A—C7—H7C	109.5	C6—C5—C4	121.12 (16)
H7B—C7—H7C	109.5	C6—C5—H5	119.4
O1—C4—C5—C6	−179.53 (17)	C2—C3—C4—C5	−2.6 (3)
N1—C6—C5—C4	1.2 (3)	C4—C3—C2—N1	2.5 (3)
C3—C4—C5—C6	0.7 (3)	C4—C3—C2—C1	−176.66 (16)
C2—N1—C6—C7	177.28 (17)	C7—C6—C5—C4	−177.33 (17)
C2—N1—C6—C5	−1.4 (3)	C6—N1—C2—C3	−0.5 (3)
C2—C3—C4—O1	177.66 (16)	C6—N1—C2—C1	178.74 (17)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O1	0.86 (1)	1.96 (1)	2.8174 (17)	173 (2)
N1—H1···O1^i	0.87 (1)	1.86 (1)	2.7154 (18)	166 (3)

Symmetry code: (i) x−1/2, −y+1/2, z.