Crystal structure of frozen o-ethoxybenzoic acid

Abstract

o-Ethoxybenzoic acid, C2H50. C6H4. COOH, an oily liquid at room temperature, crystallizes on cooling below 10 °C in the monoclinic space group P21/c, with a = 7.28 + 0.01, b = 15.02 + 0.02, c = 16.05 + 0.02/~ and ,8 = 108.27 + 0.03 °. The density calculated on the basis of eight molecules per unit cell is 1.325 g.cm-a and the density of the liquid at room temperature is 1.173 g.cm -3. The crystal structure was solved by direct methods using three-dimensional diffractometer data, measured at -10°C. The R index obtained at the end of block-diagonal least-squares refinement is 0-09 for 2469 observed reflections. The bond lengths and bond angles are in good agreement with the usually accepted values. The hydrogen atom in the carboxyl group forms intramolecular hydrogen bonding with the oxygen atom in the ethoxy group. The two independent molecules comprising the asymmetric unit differ only as to the conformation of the ethoxy group. In one molecule it is coplanar with the benzene ring and in the other it is not. The molecules are packed in a layer-like structure with a layer-to-layer distance of 3.6 ~ corresponding to half the a-axis translation. There are no unusually short intermolecular contacts.

Molecular packing modes. Carboxylic acids

“…The crystal structure of o-methoxybenzoic acid (Gopalakrishna & Cartz, 1972) is a rare excep-We may conclude in general that the hydroxyl group which does not participate in an intramolecular O-H.-. The crystal structure of o-methoxybenzoic acid (Gopalakrishna & Cartz, 1972) is a rare excep-We may conclude in general that the hydroxyl group which does not participate in an intramolecular O-H.-.…”

“…These findings are consistent with the observation that the antiplanar O=C-O-H form (lb) occurs only when the O-H bond participates in an intramolecular O-H.. • O bond, particularly in 1,2-disubstituted dicarboxylic acids as (2) shown in (2). The crystal structure of o-methoxybenzoic acid (Gopalakrishna & Cartz, 1972) is a rare excep-…”

2,6-Dimethoxy-3-nitrobenzoic acid. A hydrogen-bonded chain structure

“…In (I), the anti conformation of the acid may be stabilized by an intramolecular hydogen bond similar to that found in 2-ethoxybenzoic acid (Gopalakrishna, & Cartz, 1972). The methoxy group is coplanar with the benzene ring but the acid group is twisted 54.7 ° from the plane, nevertheless the O...O distance is 2.853 A, and the O--H-..O angle is 105.3 °.…”

Solid-State NMR and X-Ray Crystallography: Complementary Tools for Structure Determination

“…By lengthening the contact times for cross-polarization, the C-2 peak can be amplified in the solidstate spectrum. Since the crystal structure of o-ethoxybenzoic acid is known (Gopalakrishna and Cartz, 1972), the spectral similarities can be attributed to the presence of an intramolecular hydrogen bond and the absence of any strong intermolecular interactions in al! three phases.…”