5-Acetyl-4-(3-hy-droxy-phen-yl)-6-methyl-1,2,3,4-tetra-hydro-pyrimidin-2-one-tris-(hy-droxy-meth-yl)ammonium chloride (2/1).

The asymmetric unit of the title compound, 2C13H14N2O3·C3H10NO3 (+)·Cl(-), contains two independent mol-ecules (A and B) of the title pyrimidine derivative and one ion-pair of tris-(hy-droxy-meth-yl)ammonium chloride. The pyrimidine ring in each pyrimidine derivative has a half-chair conformation. Its mean plane is inclined to the benzene ring by 87.2 (3)° in mol-ecule A and 85.7 (2)° in mol-ecule B. In the crystal, the pyrimidine derivatives are connected to each other by N-H⋯O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked via O-H-Cl hydrogen bonds, forming corrugated sheets lying parallel to the bc plane. The sheets are linked via C-H⋯O hydrogen bonds, forming a three-dimensional framework. The tris-(hy-droxy-meth-yl)ammonium chloride mol-ecules are located in the cages of the framework. There are also further C-H⋯O hydrogen bonds and C-H⋯π inter-actions present in the three-dimensional framework structure. Both the cation and chloride anion of the tris-(hy-droxy-meth-yl)ammonium chloride ion pair are disordered over two positions, with a refined occupancy ratio of 0.418 (8):0.582 (8) for the cation and 0.71 (4):0.29 (4) for the anion.

The asymmetric unit of the title compound, 2C 13 H 14 N 2 O 3 Á-C 3 H 10 NO 3 + ÁCl À , contains two independent molecules (A and B) of the title pyrimidine derivative and one ion-pair of tris(hydroxymethyl)ammonium chloride. The pyrimidine ring in each pyrimidine derivative has a half-chair conformation. Its mean plane is inclined to the benzene ring by 87.2 (3) in molecule A and 85.7 (2) in molecule B. In the crystal, the pyrimidine derivatives are connected to each other by N-HÁ Á ÁO hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked via O-H-Cl hydrogen bonds, forming corrugated sheets lying parallel to the bc plane. The sheets are linked via C-HÁ Á ÁO hydrogen bonds, forming a three-dimensional framework. The tris(hydroxymethyl)ammonium chloride molecules are located in the cages of the framework. There are also further C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions present in the three-dimensional framework structure. Both the cation and chloride anion of the tris(hydroxymethyl)ammonium chloride ion pair are disordered over two positions, with a refined occupancy ratio of 0.418 (8):0.582 (8) for the cation and 0.71 (4):0.29 (4) for the anion.

Comment
As part of our ongoing investigations of pyrimidine derivatives (NizamMohideen et al., 2008a,b), the title compound was synthesized and we report herein on its crystal structure.
In the asymmetric unit of the title compound there are two independent pyrimidine derivative molecules (A and B), and one nitrilotrimethanol hydrochloride molecule (Fig. 1). All bond lengths (Allen et al., 1987) and angles in the pyrimidine derivative are within normal ranges and comparable with those in closely related structures (NizamMohideen et al., 2008a,b). The normal probability plot analyses (International Tables for X-ray Crystallography, 1974, Vol. IV, pp. 293-309) for both bond lengths and angles show that the differences between the two symmetry independent molecules are of a statistical nature.
The crystal packing is stabilized by strong N-H···O and O-H···Cl inter-and intramolecular hydrogen bonds and week intra-and intermolecular C-H···O and C-H···Cl interaction ( Fig. 2 and Table 1). In both molecules, atoms O2 and O5 act donors in strong intermolecular N-H···O hydrogen bonds via H2A and H3A with the pyrimidine ring atoms N2 and N3, respectively, of a symmetry related molecule, generating a C(6) chain (Bernstein et al., 1995). The interlinking of A and B molecules via strong N-H···O (N1-H1A···O4 and N4-H4A···O1) hydrogen bond generates infinite chains running along the a axis direction. The molecular packing is further stabilized by C-H···π interactions involving a methylene H atom of the tris(hydroxymethyl)ammonium cation and the pyrimidine ring of an adjacent molecule ( Table   1). The crystal structure is further stabilized by O-H···Cl hydrogen bonds to form a three-dimensional supramolecular framework (Table 1 and

Experimental
A mixture of urea, 3-hydroxybenzaldehyde and acetyl acetone in the molar ratio 1.5:1:1 was ground in a mortar and pestle, in the presence of a catalytic amount of phosphoric acid, for 30 minutes, and then poured into a beaker containing ice cold water. The product obtained, 6-methyl-5-acetyl-3,4-dihydro-4-(3-hydroxyphenyl)-2(1H)-pyrimidinone [I], was filtered, washed with water and dried in air. Under ice cold conditions a few drops of triethylamine (0.01 mole) were added to chloroacetyl chloride (0.01 mole). 0.01 mol of [I] was added and then the mixture was stirred well for 10 min.
Ethanol (20 ml) was then added and the mixture irradiated with microwave irradiation for 30 s. On evaporation of the solvent, the title solid product was obtained. It was recrystallized from ethanol giving brown block-like crystals suitable for X-Ray diffraction analysis.

Refinement
The tris(hydroxymethyl)ammonium chloride molecule is disordered both thermally and positionally; over two positions with refined occupancy ratios of 0.418 (8)   A view along the a axis of the crystal packing of the title compound. The hydrogen bonds are shown as dashed lines (see Table 1 for details; H atoms not involved in hydrogen bonding have been omitted for clarity).  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.21 e Å −3 Δρ min = −0.23 e Å −3 Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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 > σ(F 2 ) is used only for calculating R-factors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (