The crystal structure of anthranilic acid

The crystal structure of the form of anthranilic acid stable at room temperature has been determined from three-dimensional X-ray diffraction data. 1416 structure amplitudes were used in refining the positional and anisotropic thermal parameters, resulting in a discrepancy index R = 7.0%, and e.s.d. of 0.0045 $\overset{\circ}{\mathrm A}$ in the atomic coordinates. There are two nonequivalent molecules per lattice point in the space group P 2$_1$cn, and the analysis shows these two molecules to have considerably different bond lengths. This evidence, taken together with the hydrogen-bonding system, indicates that one molecule is neutral, while the other is a zwitterion.