Redetermination of 1-naphthaleneacetic acid

The crystal structure of the title compound, C12H10O2, was originally determined by Rajan [Acta Cryst. (1978). B34, 998–1000] using intensity data estimated from Weissenberg films. This redetermination provides a structure with significantly improved precision with respect to the geometric parameters. In the crystal structure, intermolecular O—H⋯O hydrogen bonds, weak C—H⋯O hydrogen bonds and C—H⋯π interactions link the molecules into a two-dimensional sheet lying parallel to (100).

The crystal structure of the title compound, C 12 H 10 O 2 , was originally determined by Rajan [Acta Cryst. (1978). B34, 998-1000] using intensity data estimated from Weissenberg films. This redetermination provides a structure with significantly improved precision with respect to the geometric parameters. In the crystal structure, intermolecular O-HÁ Á ÁO hydrogen bonds, weak C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions link the molecules into a two-dimensional sheet lying parallel to (100).

Experimental
Data collection: SMART (Bruker, 2001); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: PLATON.  Allen, 2002, Bruno et al., 2002 reveals that the structure of the title compound (I) was first reported (Rajan, 1978) with R = 0.129 for 776 observed reflections. However, the published report did not identify any supramolecular aggregation beyond the formation of a hydrogen-bonded dimers. We have now taken the opportunity to redetermine the structure of the title compound using data collected at 200 K.
In (I), we find the same phase at 200 K as those previously reported at ambient temperature. During the refinement of (I), we have refined the structure without any constraints, and the current precision is significantly better than those reported previously. Thus, for example, the previously reported s.u. values for the C-O bonds are 0.01 (Rajan, 1978); whereas from the present refinement of (I), these s.u. values are only 0.002. In addition, the R value is very much lower for the present refinement (0.0488). The dihedral angles between the naphthalene-ring plane (C1 to C10) and the carboxyl plane (C11/C12/O1/O2) are 80.6 (1)° ( Fig.1) for the title compound and 81.3 (1)° for the original detemination, respectively. No unusual molecular features are worthy of discussion.
In compound (I), the molecules are linked by a combination of O-H···O, weak C-H···O hydrogen bonds and C-H···π interaction, into a two-dimensional network. In more detail, the supramolecular aggregation can be analyzed in therms of three aspects. First, the O1 atom in the molecule at (x, y, z), act as the hydrogen-bonding donor, via H1 atom, to the O2 atom in the molecule at (-x, -y, 2 -z), forming a discrete hydrogen-bonding dimer (Fig.2). Secondly, atom C11 at (x, y, z) acts as hydrogen-bond donor (Table 1) to the C1/C6-C10 aryl ring at (x, y -1,z), forming a C-H···π interaction, which linked the dimers into a one-dimensional chain running parallel to the [010] direction (Fig.2). Finally, these adjacent [010] chains are linked together by a weak C3-H3···O2 hydrogen bond [C···O=3.540 (2) Å, symmetry code: -x, -1/2 + y, 3/2 -z), forming the final two-dimensional sheet lying parallel to the (100) plane (Fig.3). No other direction-specific interactions are observed between the neighbouring sheets.
Experimental 1-Naphthalene-acetic acid (I), was obtained unexpectedly by reaction of mixing 2:1:1 equivalent molar amount of (I), 4,4'bi-pyridine and Mn(ClO 4 ) 2 .2(H 2 O) in 95% methanol (20 ml). The mixture was stirred for 30 minutes at 330 K and then filtered. Colorless needle crystals of (I) suitable for single-crystal X-ray diffraction analysis were grown at the bottom of the vessel in two weeks after slow evaporation of the solution.

Refinement
All H atoms bonded to C atoms were located in difference maps and then treated as ring with C-H = 0.93 Å(aromatic), 0.97 Å (methylene) and refined in a riding mode [U iso (H) = 1.2U eq (C)]. H1 atom was found in the difference map and the O-H distance was refined freely [the refined distances are given in Table 1 Fig. 1. Molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.   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 > σ(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.