Diethyl 4-hydroxy-4-methyl-6-oxo-2-phenylcyclohexane-1,3-dicarboxylate

In the title molecule, C19H24O6, the cyclohexanone ring adopts a chair conformation. The dihedral angle between the phenyl ring and the best plane through the six atoms of the cyclohexanone ring is 89.68 (7)°. In the crystal structure, molecules are linked via pairs of intermolecular O—H⋯O hydrogen bonds into centrosymmetric dimers and these dimers are connected by C—H⋯O interactions into columns down the a axis.

In the title molecule, C 19 H 24 O 6 , the cyclohexanone ring adopts a chair conformation. The dihedral angle between the phenyl ring and the best plane through the six atoms of the cyclohexanone ring is 89.68 (7) . In the crystal structure, molecules are linked via pairs of intermolecular O-HÁ Á ÁO hydrogen bonds into centrosymmetric dimers and these dimers are connected by C-HÁ Á ÁO interactions into columns down the a axis.

Comment
Phenylcyclohexane is a highly valued chemical compound widely used as plasticizer in plastics, coatings and adhesive fields.
The molecular structure of (I), is shown in Fig (Table 1) into columns down the a axis.

Experimental
Ethylacetoacetate (19.1 ml, 0.15 mol) and piperidine (9 ml) were dissolved in 150 ml of dry benzene. Then benzaldehyde (15.3 ml, 0.15 mol) was added drop-wise at room temperature over 20 min. The reaction mixture was slowly brought to boil and refluxed for 2 hours with constant stirring with periodic TLC monitoring. After cooling, organic layer was washed with cold aqueous 10 % sodium carbonate, water and 5 % acetic acid. Then the organic layer was dried and evaporated under reduced pressure and the crude product synthesis of 2-benzylidene-malonic acid diethyl ester was purified by crystallization from methanol. Separately ethylacetoacetate (8 mmol) was dissolved in ethanol (10 ml) and sodium acetate (6 mmol) was dissolved in water (2 ml) and then slowly added to the ethanol solution at room temperature. The resulting solution was stirred for 10 minutes and then added the 2-benzylidene-malonic acid diethyl ester (3.2 mmol) slot-wise. The reaction mixture was stirred for 24 hrs at room temperature. The solid formed was filtered and washed with water and recrystalised in ethanol. (yield 40 %, m.p 510-512 K).

Refinement
The hydroxyl H atom was located from a difference Fourier map and refined freely. The remaining H atoms were positioned geometrically [C-H = 0.93-0.98 Å] and were refined using a riding model, with U iso (H) = 1.2U eq (C).  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.