1-(4-Methyl-1-naphthyl)ethanone

In the molecule of the title compound, C13H12O, the two aromatic rings are oriented at a dihedral angle of 2.90 (3)°. An intramolecular C—H⋯O hydrogen bond results in the formation of a non-planar six-membered ring, which adopts an envelope conformation. In the crystal structure, intermolecular C—H⋯O hydrogen bonds link the molecules.

In the molecule of the title compound, C 13 H 12 O, the two aromatic rings are oriented at a dihedral angle of 2.90 (3) . An intramolecular C-HÁ Á ÁO hydrogen bond results in the formation of a non-planar six-membered ring, which adopts an envelope conformation. In the crystal structure, intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules.

Comment
The title compound is a dye and plastic processing aid of intermediate, 1,4-naphthalenedicarboxylic acid. As part of our ongoing studies in this area, we report herein its crystal structure.
In the title compound ( Fig. 1), the bond lengths (Allen et al., 1987) and angles are within normal ranges. Rings A (C3-C8) and B (C1-C3/C8-C10) are, of course, planar and the dihedral angle between them is A/B = 2.90 (3)°. The intramolecular C-H···O hydrogen bond (Table 1) results in the formation of a nonplanar six-membered ring C (C2-C4/C12/O/H2A) adopting envelope conformation with O atom displaced by -0.533 (3) Å from the plane of the other ring atoms.
In the crystal structure, intermolecular C-H···O hydrogen bonds (Table 1) link the molecules (Fig. 2), in which they may be effective in the stabilization of the structure.

Experimental
In a three-necked flask, naphthalene (256.0 g, 2.00 mol), paraformaldehyde (110.0 g, 1.22 mol), glacial acetic acid (260 ml), concentrated hydrochloric acid (362 ml) and phosphoric acid (165 ml, 85%) are heated with efficient stirring in a water bath at 353-358 K for 6 h. The product is washed two times with cold water (1 liter), a solution of potassium carbonate (20.0 g) in cold water (500 ml), and finally with cold water (500 ml). Ether (200 ml) is added to the oil layer and the solution is given a preliminary drying with anhydrous potassium carbonate (10.0 g) for 1 h. The lower aqueous layer is separated and the ether solution again dried with potassium carbonate (20.0 g) for 8-10 h. The ether solution is distilled first at atmospheric pressure to remove the ether, and then followed by distillation under reduced pressure to obtain 1-chloromethylnaphthalene. In a three-necked flask, magnesium (63.2 g), absolute ether (100 ml), a crystal of iodine, a solution of 1-chloromethylnaphthalene (150.0 g, 0.85 mol) in absolute ether (750 ml) and absolute ether (1080 ml) are mixed, and the ether solution of the chloride is added to the mixture in 5 h, and then stirred and heated at reflux for an additional 1 h to obtain 1-methylnaphthalene. The yield was 88-92% (Grummitt & Buck, 1943). Acetyl chloride (39.3 g, 0.48 mol, 38 ml) is added over 45 min to a stirred mixture of 1-methylnaphthalene (Aldrich) (67.0 g, 0.48 mol), dry dichloromethane (340 ml) and finely ground anhydrous aluminium chloride (76.0 g, 0.57 mol) at 273 K. After the addition is completed, the mixture is stirred at ambient temperature for 4 h, and then heated under reflux for 2.5 h (Dixon et al., 1981). The reaction solution is washed with hydrochloric acid many times. The aqueous phase followed by distillation under reduced pressure gave the title compound (yield; 71%) (Merritt & Braun, 1950). Crystals suitable for X-ray analysis are obtained by slow evaporation of an petroleum ether solution.

Refinement
H atoms were positioned geometrically, with C-H = 0.93 and 0.96 Å for aromatic and methyl H, respectively, and constrained to ride on their parent atoms with U iso (H) = xU eq (C), where x = 1.5 for methyl H and x = 1.2 for aromatic H atoms. Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen bond is shown as dashed line.