2,6-Di-tert-butyl-4-(dimethylaminomethyl)phenol

The title compound, C17H29NO, is an important hindered phenol derivative. The asymmetric unit contains two molecules. Molecules interact through O—H⋯N hydrogen bonds to form a tetramer arranged around a twofold rotation axis.

The title compound, C 17 H 29 NO, is an important hindered phenol derivative. The asymmetric unit contains two molecules. Molecules interact through O-HÁ Á ÁN hydrogen bonds to form a tetramer arranged around a twofold rotation axis.

Comment
Hindered phenol antioxidants are widely used in polymers and lubricants. It could protect polymers by increasing both their process stability and long-term stability against oxidative degradation (Yamazaki & Seguchi, 1997). Moreover, ester of 3,5-di-tert-butyl-4-hydroxyphenol acetic acid is one important kind of antioxidant derivative. An important route to prepare these compounds is to react an α-halo ester compound with the title compound in the presence of a strong base (Eggensperger et al., 1974(Eggensperger et al., , 1976Eggensperger et al., 1976;Ciba-Geigy AG, 1978). The title compound is ususlly called a Mannich base. The title compound was prepared from 4-bromomethyl-2,  can also be easily obtained by a Mannich reaction from 2,6-di-tert-butylphenol,formaldehyde and dimethylamine (Coffield, 1965;Coffield & Mich, 1965).
The asymmetric unit of the title compound contains two molecules which are linked by a weak O-H···N hydrogen bond ( Fig. 1). Each pseudo dimer interacts with a symmetry related one to build up like a crown arranged around axis parallele to the b axis through O-H··· hydrogen bonds (Table 1, Fig. 2).

Experimental
The 4-bromomethyl-2,6-di-tert-butyl-phenol was synthesized according to the method described by Rieker(Rieker et al.,1968). Dimethylamine (2.7 g, 0.06 mol) and 4-bromomethyl-2,6-di-tert-butyl-phenol (9.0 g, 0.03 mol) were added, with stirring to THF(60 ml)at 273 K. The reaction mixture was stirred at 273 K for a further 2 h. The solvent THF was evaporated under reduced pressure and the residual was washed with water (30 ml). The product (7.39 g) was obtained in a yield of 93.6%. Suitable crystals were obtained by slow evaporation of a mixture of ethyl acetate and ethanol.

Refinement
All H atoms attached to C atoms were fixed geometrically and treated as riding with C-H = 0.93 Å (aromatic) and 0.96 Å (methyle) with U iso (H) = 1.2(aromatic) or 1.5(methyle)U eq (C). H atoms of hydroxyle group were located in difference Fourier maps and included in the subsequent refinement using restraints (O-H= 0.85 (1) Å) with U iso (H) = 1.5U eq (O). In the final stage of refinement, they were treated as riding on their parent O atoms.
In the absence of significant anomalous scattering, the absolute configuration could not be reliably determined and then the Friedel pairs were merged and any references to the Flack parameter were removed.
supplementary materials sup-2 Figures Fig. 1. View of the two crystallygraphically independent molecules with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen bond is shown as dashed line. H atoms are represented as small spheres of arbitrary radii.   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 > 2sigma(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.