Anthranilic acid is an aromatic acid with the formula C6H4(NH2)(CO2H) and has a sweetish taste.[5][6][7] The molecule consists of a benzene ring, ortho-substituted with a carboxylic acid and an amine. As a result of containing both acidic and basic functional groups, the compound is amphoteric. Anthranilic acid is a white solid when pure, although commercial samples may appear yellow. The anion [C6H4(NH2)(CO2)]−, obtained by the deprotonation of anthranilic acid, is called anthranilate. Anthranilic acid was once thought to be a vitamin and was referred to as vitamin L1 in that context, but it is now known to be non-essential in human nutrition.[8]
Structure
Although not usually referred to as such, it is an amino acid. Solid anthranilic acid typically consists of both the amino-carboxylic acid and the zwitterionic ammonium carboxylate forms, and has a monoclinic crystal structure with space group P21.[9] It is triboluminescent.[10] Above 81 °C (178 °F; 354 K), it converts to an orthorhombic form with space group Pbca, which is not triboluminescent; a non-triboluminescent monoclinic phase with similar structure is also known.[10]
Production
Many routes to anthranilic acid have been described. Industrially it is produced from phthalic anhydride, beginning with amination:
C6H4(C(O)NH2)CO2Na + HOCl → C6H4NH2CO2H + NaCl + CO2
A related method involves treating phthalimide with sodium hypobromite in aqueous sodium hydroxide, followed by neutralization.[12] In the era when indigo dye was obtained from plants, it was degraded to give anthranilic acid.
Anthranilic acid was first obtained by base-induced degradation of indigo.[13]
^Hardy, Mark R. (1997). "Glycan Labeling with the Flurophores 2-Aminobenzamide and Antranilic Acid". In Townsend, R. Reid; Hotchkiss, Arland T. Jr. (eds.). Techniques in Glycobiology. Marcel Dekker, Inc. p. 360. ISBN9780824798222 – via Google Books.
^ abHardy, Gordon E.; Kaska, William C.; Chandra, B. P.; Zink, Jeffrey I. (March 1981). "Triboluminescence-structure relationships in polymorphs of hexaphenylcarbodiphosphorane and anthranilic acid, molecular crystals, and salts". Journal of the American Chemical Society. 103 (5): 1074–1079. doi:10.1021/ja00395a014.
^Vogel's Textbook of Practical Organic Chemistry, 4th Ed., (B. S. Furniss et al., Eds.) (1978), p.666, London: Longman.
^Sheibley, Fred E. (1943). "Carl Julius Fritzsche and the discovery of anthranilic acid, 1841". Journal of Chemical Education. 20 (3): 115. Bibcode:1943JChEd..20..115S. doi:10.1021/ed020p115.
^Angelos SA, Meyers JA (1985). "The isolation and identification of precursors and reaction products in the clandestine manufacture of methaqualone and mecloqualone". Journal of Forensic Sciences. 30 (4): 1022–1047. doi:10.1520/JFS11044J. PMID3840834.