1-Carboxynaphthalen-2-yl acetate monohydrate

In the title compound, C13H10O4·H2O, both the carboxylic acid [Car—Car—C—O = −121.1 (2)°, where ar = aromatic] and the ester [Car—Car—O—C = −104.4 (3)°] groups lie out of the mean plane of the conjugated aromatic system. In the crystal, the organic molecule is hydrogen bonded to water molecules through the ester and carboxy moieties, forming chains along the a-axis direction. The methyl H atoms of the acetoxy group are disordered over two equally occupied sites.

In the title compound, C 13 H 10 O 4 ÁH 2 O, both the carboxylic acid [C ar -C ar -C-O = À121.1 (2) , where ar = aromatic] and the ester [C ar -C ar -O-C = À104.4 (3) ] groups lie out of the mean plane of the conjugated aromatic system. In the crystal, the organic molecule is hydrogen bonded to water molecules through the ester and carboxy moieties, forming chains along the a-axis direction. The methyl H atoms of the acetoxy group are disordered over two equally occupied sites.
Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: SET4 in CAD-4 Software; data reduction: HELENA (Spek, 1996); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL2013. It has been extensively shown that the spatial relationship between reacting groups have drastic effects on the mechanism and speed of intramolecular reactions (Orth et al., 2010). Recently, we have reported the structure of 2-carboxy-1-naphtyl acetate (Souza et al., 2007) and 3-acetoxy-2-naphthoic acid , constitutional isomers of the title compound. In a detailed experimental and theoretical investigation, it has been shown that although 2-carboxy-1-naphthyl acetate and 3-acetoxy-2-naphthoic acid show similar structures, they display very different hydrolysis mechanisms ). In the current report, we show the crystal structure of 1-carboxy-2-naphthyl acetate (I) which may be a useful molecule for further investigations related to proximity and orientation effects.
A projection of the crystal structure of (I) is shown in Fig. 1. The carboxy group lies out of the mean aromatic plane, with a C1-C2-C13-O3 torsion angle of -121.1 (2)°, while in the structure of 1-naphthoic acid the equivalent torsion is 7.73° (Fitzgerald & Gerkin, 1993). Similarly, the acetyl group lies almost perpendicular to the aromatic ring, with C2-C1-O1-C11 tosrion angle of -104.4 (3)°. The organic fragment is hydrogen bonded to water molecules with interactions centered in both the COOH group and the acetyl group forming one-dimensional polymeric structure parallel to crystallographic a axis (Fig. 2).

Experimental
The title compound was prepared by following the procedure reported in the literature (Chattaway, 1931). In an Erlenmeyr flask containing a magnetic bar, 100 ml of water, 1.40 g of KOH and 2.24 g of 2-hydroxy-1-naphthoic acid were dissolved. The liquid was cooled and mixed with crushed ice. Under vigorous mixing, 1.40 ml of acetic anhydride was quickly added, forming a white precipitate. The reaction was allowed to warm to room temperature, acidified with aqueous HCl, and the white material was filtered. After recrystallization in aqueous ethanol a white powder that melts at 375-376 K was obtained. Crystals suitable for X-ray diffraction were obtained by dissolving about 10 mg of the as prepared material in 5 ml of CHCl 3 in a 10 ml glass vial and the flask was kept in a saturated petroleum ether atmosphere at 293 K.

Refinement
All non-H atoms were refined with anisotropic displacement parameters. H atoms were placed at their idealized positions with distances of 0.93 Å for C-H Ar and 0.96 Å for CH 3 group. Their U eq were fixed at 1.2 and 1.5 times U iso of the preceding atom for aromatic and methyl group, respectively. H atoms of the methyl group were added as idealized disordered over two positions. The hydrogen atoms of the acid group and water molecule were located from the Fourier difference map and treated as free atoms.

Figure 1
The molecular structure of the title compound with labeling scheme. Displacement ellipsoids are shown at the 40% probability level.  One-dimensional polymer parallel to a axis formed by hydrogen bonds.