2-Isopropyl-6-methyl­pyrimidin-4(3H)-one

The mol­ecular structure of the title compound, C₈H₁₂N₂O, indicates that 2-isopropyl-6-methyl­pyrimidin-4-ol (the enol–form) undergoes an enol-to-keto tautomerism during the crystallization process. The pyrimidin-4(3H)-one group is essentially planar, with a maximum deviation of 0.081 (1) Å for the O atom. In the crystal structure, symmetry-related mol­ecules are linked into centrosymmetic dimers via pairs of inter­molecular N—H...O hydrogen bonds, generating R₂²(8) rings. These dimers are stacked along the a axis.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.001 Å
• R factor = 0.039
• wR factor = 0.103
• Data-to-parameter ratio = 16.0

checkCIF/PLATON results

No syntax errors found



Alert level C
SHFSU01_ALERT_2_C  Test not performed. _refine_ls_shift/su_max and
            _refine_ls_shift/esd_max not present.
            Absolute value of the parameter shift to su ratio given   0.001
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600          5

Alert level G
PLAT063_ALERT_4_G Crystal Size Likely too Large for Beam Size ....       0.74 mm
PLAT128_ALERT_4_G Alternate Setting of Space-group P21/c   .......      P21/n
PLAT720_ALERT_4_G Number of Unusual/Non-Standard Labels ..........          1

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   3 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   4 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Pyrimidine derivatives are very important molecules in biology and have many application in the areas of pesticide and pharmaceutical agents (Condon et al., 1993). For example, imazosulfuron, ethirmol and mepanipyrim have been commercialized as agrochemicals (Maeno et al., 1990). Pyrimidine derivatives have also been developed as antiviral agents, such as AZT, which is the most widely used anti-AIDS drug (Gilchrist, 1997). Recently, a new series of highly active herbicides of substituted azolylpyrimidines were reported (Selby et al., 2002). Keeping in view of the importance of the pyrimidine derivatives, the title compound (I) was presented.

The title molecule, (Fig. 1), exists in the keto-form although 2-isopropyl-4-hydroxy-6-methylpyrimidine (the enol-form) was used for crystallization. This indicates the compound undergoes an enol-to-keto tautomerism during the crystallization process (Fig. 3). The C2═O1 bond length is 1.2497 (11) Å. The pyrimidin-4(3H)-one group is essentially planar with a maximum deviation of 0.081 (1) Å for atom O1. In the crystal structure (Fig. 2), adjacent molecules are linked via pairs of intermolecular N—H···O hydrogen bonds to form dimers, generating R₂²(8) rings (Bernstein et al., 1995). These dimers are stacked along the a-axis.

Related literature

For applications of pyridinium derivatives, see: Condon et al. (1993); Maeno et al. (1990); Gilchrist (1997); Selby et al. (2002). For hydrogen-bond motifs, see: Bernstein et al. (1995). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).

S2. Experimental

Hot methanol solution (20 ml) of 2-isopropyl-4-hydroxy-6-methylpyrimidine (46 mg, Aldrich) was warmed over a heating magnetic stirrer for 5 minutes. The resulting solution was allowed to cool slowly at room temperature. Crystals of the title compound appeared from the mother liquor after a few days.

S3. Refinement

All H atoms were located in a difference Fourier map and refined freely.

Computing details

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures

	Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. The crystal packing of the title compound, viewed approximately along the a-axis. Hydrogen bonds are shown as dashed lines.
	Fig. 3. The title compound and the tautomeric form.

2-Isopropyl-6-methylpyrimidin-4(3H)-one

Crystal data

C8H12N2O	F(000) = 328
Mr = 152.20	Dx = 1.245 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 2995 reflections
a = 4.8627 (2) Å	θ = 2.9–30.0°
b = 22.6320 (8) Å	µ = 0.08 mm^−1
c = 7.4228 (3) Å	T = 100 K
β = 96.495 (2)°	Needle, colourless
V = 811.66 (5) Å^3	0.74 × 0.14 × 0.07 mm
Z = 4

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	2371 independent reflections
Radiation source: fine-focus sealed tube	1958 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.026
φ and ω scans	θmax = 30.1°, θmin = 1.8°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −5→6
Tmin = 0.940, Tmax = 0.994	k = −26→31
7806 measured reflections	l = −10→10

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.039	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.103	All H-atom parameters refined
S = 1.06	w = 1/[σ^2(Fo^2) + (0.049P)^2 + 0.163P] where P = (Fo^2 + 2Fc^2)/3
2371 reflections	(Δ/σ)max < 0.001
148 parameters	Δρmax = 0.32 e Å^−3
0 restraints	Δρmin = −0.20 e Å^−3

Special details

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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 (Ų)

	x	y	z	Uiso*/Ueq
O1	0.77782 (15)	0.03007 (3)	0.81600 (9)	0.02023 (18)
N1	0.43265 (17)	−0.13343 (3)	0.84671 (10)	0.01613 (18)
N2	0.75959 (17)	−0.06091 (3)	0.94759 (10)	0.01473 (17)
C1	0.64511 (19)	−0.11546 (4)	0.95755 (12)	0.01455 (19)
C2	0.6596 (2)	−0.01885 (4)	0.82081 (12)	0.0158 (2)
C3	0.4232 (2)	−0.03768 (4)	0.70385 (12)	0.0169 (2)
C4	0.32239 (19)	−0.09370 (4)	0.71759 (12)	0.0156 (2)
C5	0.0868 (2)	−0.11656 (5)	0.58916 (13)	0.0190 (2)
C6	0.7737 (2)	−0.15603 (4)	1.10544 (13)	0.01614 (19)
C7	0.8468 (3)	−0.21559 (5)	1.02578 (15)	0.0249 (2)
C8	0.5752 (2)	−0.16347 (5)	1.25028 (14)	0.0222 (2)
H1N2	0.915 (3)	−0.0510 (7)	1.0283 (19)	0.034 (4)*
H3A	0.338 (3)	−0.0101 (6)	0.6146 (18)	0.025 (3)*
H5A	−0.064 (3)	−0.1299 (6)	0.655 (2)	0.036 (4)*
H5B	0.011 (3)	−0.0864 (7)	0.503 (2)	0.044 (4)*
H5C	0.151 (3)	−0.1505 (6)	0.5237 (19)	0.034 (4)*
H6A	0.946 (3)	−0.1369 (5)	1.1613 (16)	0.018 (3)*
H7A	0.922 (3)	−0.2424 (6)	1.124 (2)	0.031 (3)*
H7B	0.984 (3)	−0.2117 (6)	0.9349 (19)	0.031 (4)*
H7C	0.681 (3)	−0.2348 (6)	0.9648 (19)	0.036 (4)*
H8A	0.661 (3)	−0.1874 (6)	1.3518 (19)	0.029 (3)*
H8B	0.408 (3)	−0.1849 (6)	1.1978 (18)	0.031 (4)*
H8C	0.519 (3)	−0.1249 (6)	1.2967 (19)	0.032 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0210 (4)	0.0159 (3)	0.0229 (4)	−0.0031 (3)	−0.0012 (3)	0.0032 (3)
N1	0.0159 (4)	0.0163 (4)	0.0157 (4)	−0.0010 (3)	0.0002 (3)	−0.0005 (3)
N2	0.0146 (4)	0.0143 (4)	0.0150 (4)	−0.0008 (3)	0.0005 (3)	0.0004 (3)
C1	0.0146 (4)	0.0146 (4)	0.0146 (4)	0.0003 (3)	0.0026 (3)	−0.0007 (3)
C2	0.0159 (4)	0.0161 (4)	0.0156 (4)	0.0005 (3)	0.0028 (3)	0.0007 (3)
C3	0.0165 (5)	0.0185 (4)	0.0153 (4)	0.0014 (3)	0.0006 (3)	0.0019 (3)
C4	0.0143 (4)	0.0185 (5)	0.0142 (4)	0.0005 (3)	0.0019 (3)	−0.0018 (3)
C5	0.0164 (5)	0.0227 (5)	0.0172 (4)	−0.0011 (4)	−0.0013 (3)	−0.0022 (4)
C6	0.0157 (4)	0.0151 (4)	0.0168 (4)	−0.0011 (3)	−0.0015 (3)	0.0009 (3)
C7	0.0301 (6)	0.0172 (5)	0.0260 (5)	0.0036 (4)	−0.0026 (4)	−0.0004 (4)
C8	0.0202 (5)	0.0268 (5)	0.0193 (5)	−0.0016 (4)	0.0012 (4)	0.0061 (4)

Geometric parameters (Å, º)

O1—C2	1.2497 (11)	C5—H5B	0.978 (16)
N1—C1	1.3105 (12)	C5—H5C	0.978 (15)
N1—C4	1.3777 (12)	C6—C7	1.5297 (14)
N2—C1	1.3595 (12)	C6—C8	1.5332 (14)
N2—C2	1.3874 (12)	C6—H6A	0.990 (12)
N2—H1N2	0.937 (15)	C7—H7A	0.985 (14)
C1—C6	1.5114 (13)	C7—H7B	1.004 (14)
C2—C3	1.4254 (13)	C7—H7C	0.980 (15)
C3—C4	1.3672 (13)	C8—H8A	0.982 (14)
C3—H3A	0.968 (13)	C8—H8B	0.987 (14)
C4—C5	1.4972 (13)	C8—H8C	0.988 (15)
C5—H5A	0.973 (16)
C1—N1—C4	116.83 (8)	H5A—C5—H5C	107.8 (12)
C1—N2—C2	123.08 (8)	H5B—C5—H5C	109.9 (12)
C1—N2—H1N2	119.2 (9)	C1—C6—C7	110.47 (8)
C2—N2—H1N2	117.7 (9)	C1—C6—C8	109.54 (8)
N1—C1—N2	123.11 (9)	C7—C6—C8	111.50 (8)
N1—C1—C6	119.97 (8)	C1—C6—H6A	107.5 (7)
N2—C1—C6	116.92 (8)	C7—C6—H6A	108.9 (7)
O1—C2—N2	120.02 (9)	C8—C6—H6A	108.9 (7)
O1—C2—C3	126.12 (9)	C6—C7—H7A	109.9 (8)
N2—C2—C3	113.86 (8)	C6—C7—H7B	112.5 (8)
C4—C3—C2	120.21 (9)	H7A—C7—H7B	109.4 (11)
C4—C3—H3A	121.2 (8)	C6—C7—H7C	110.8 (9)
C2—C3—H3A	118.6 (8)	H7A—C7—H7C	106.5 (12)
C3—C4—N1	122.85 (9)	H7B—C7—H7C	107.6 (11)
C3—C4—C5	121.86 (9)	C6—C8—H8A	110.7 (8)
N1—C4—C5	115.27 (8)	C6—C8—H8B	109.4 (8)
C4—C5—H5A	110.6 (9)	H8A—C8—H8B	106.8 (12)
C4—C5—H5B	112.3 (9)	C6—C8—H8C	111.6 (8)
H5A—C5—H5B	107.2 (12)	H8A—C8—H8C	109.3 (11)
C4—C5—H5C	108.9 (8)	H8B—C8—H8C	109.0 (11)
C4—N1—C1—N2	−1.11 (13)	C2—C3—C4—N1	2.79 (14)
C4—N1—C1—C6	178.69 (8)	C2—C3—C4—C5	−175.72 (8)
C2—N2—C1—N1	0.98 (14)	C1—N1—C4—C3	−0.79 (13)
C2—N2—C1—C6	−178.83 (8)	C1—N1—C4—C5	177.82 (8)
C1—N2—C2—O1	−178.41 (8)	N1—C1—C6—C7	52.88 (12)
C1—N2—C2—C3	0.98 (12)	N2—C1—C6—C7	−127.31 (9)
O1—C2—C3—C4	176.61 (9)	N1—C1—C6—C8	−70.32 (11)
N2—C2—C3—C4	−2.73 (13)	N2—C1—C6—C8	109.50 (9)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H1N2···O1^i	0.937 (15)	1.844 (14)	2.7809 (11)	178.7 (10)

Symmetry code: (i) −x+2, −y, −z+2.