4,4′-Dimethyl-2,2′-[imidazolidine-1,3-diylbis(methylene)]diphenol

The imidazolidine ring in the title compound, C19H24N2O2, adopts a twist conformation and its mean plane (r.m.s. deviation = 0.19 Å) makes dihedral angles of 72.38 (9) and 71.64 (9)° with the two pendant aromatic rings. The dihedral angle between the phenyl rings is 55.94 (8)°. The molecular structure shows the presence of two intramolecular O—H⋯N hydrogen bonds between the phenolic hydroxyl groups and N atoms with graph-set motif S(6). In the crystal, C—H⋯O hydrogen bonds lead to the formation of chains along the b-axis direction.

Data collection: CrysAlis PRO (Agilent, 2010); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: Superflip (Palatinus & Chapuis 2007); program(s) used to refine structure: JANA2006 (Petříček et al., 2006); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: JANA2006. The 1,3-imidazolidine system is intriguing because it is present in biologically active molecules with anti-inflammatory and analgesic properties (Sharma et al., 2001). In our current investigations of factors which influence intramolecular hydrogen bond strength in 1,3-imidazolidine-bridged bis(phenols) (Rivera et al., 2011(Rivera et al., , 2012, we turn our attention to title compound (I) because the methyl substituent at the para-position in aromatic rings is an electron-donating group which makes the negative charge of hydroxyl group.

Experimental
For the originally reported synthesis, see: Rivera et al. (1993)

Refinement
The position of hydrogen atoms attached to carbon were fixed in geometrically expected positions, with C-H distance 0.96 Å. On the other hand, positions of H atoms of OH groups were refined without any restrain or constrain. ADP of all hydrogen atoms were fixed as 1.2 multiple of the equivalent isotropic ADP of their parent atom

Figure 1
A perspective view of the title compound. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Hydrogen bonds are drawn as dashed lines.

Figure 2
Packing of the molecules of the title compound view along b axis.

Special details
Experimental. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F 2 for refinement carried out on F and F 2 , respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement. The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.