Synthesis of Orthanilic Acid by the Reaction of Aniline with Sulfamic Acid

Abstract

It has been found that reaction of aniline with sulfamic acid gave ammonium orthanilate through the. reaction intermediates ammonium N-phenylsulfamate.
When a mixture of 1 mole of sulfamic acid and 4 moles of aniline was stirred at 160°C for 12 hr, orthanilic acid (0.42 mol) sulfanilic acid (0.35 mol) and a small amount of aniline disulfonic acid was obtained. The separation of orthanilic acid and sulfanilic acid was per- formed successfully by means of the difference of solubilities in aqueous pottassium hydroxide.
The total yields of orthanilic acid and sulfanilic acid were 35.5% and 24.4% respectively based on sulfamic acid. This method can be conveniently used for the preparation of orthanilic arid.