The unsubstituted ortho-amidino benzoic acid: crystal structure, characterization and p K determination.

The simplest o-amidino benzoic acid-2-(amino(imino)methyl)benzoic acid-has been isolated in 23 % yield as a side product of the reaction of phthalonitrile and ammonia along with desired 1-imino-1 H-isoindol-3-amine. This amidino acid was fully characterized by nuclear magnetic resonance, IR spectroscopy, mass spectrometry; pK values were also determined. X-ray diffraction study and quantum chemical calculations revealed that in the solid state it exists as a zwitterion that is stabilized by intermolecular hydrogen bonds. [ABSTRACT FROM AUTHOR]