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 R 2 2(8) rings. These dimers are stacked along the a axis.

The molecular structure of the title compound, C 8 H 12 N 2 O, indicates that 2-isopropyl-6-methylpyrimidin-4-ol (the enolform) 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-HÁ Á ÁO hydrogen bonds, generating R 2 2 (8) rings. These dimers are stacked along the a axis.
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 (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.

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.

Refinement
All H atoms were located in a difference Fourier map and refined freely. Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

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 Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.