Anthranilic acid

Anthranilsäure

2-Aminobenzoic-acid-3D-balls

anthranilate is the precursor to the amino acid tryptophan.

Anthranilic acid (also known as o-amino-benzoic acid) is an aromatic acid characterized by the formula C6H4(NH2)(CO2H). The molecule comprises a benzene ring, classified under aromatic compounds, with two ortho-functional groups: a carboxylic acid and an amine. Due to these properties, anthranilic acid exhibits amphoteric behavior. Typically, pure anthranilic acid appears as a white solid, although commercial variants may have a yellowish tint. Occasionally, it's referred to as vitamin L1 and is known for its slightly sweet taste. The anion [C6H4(NH2)(CO2)]-, derived from the deprotonation of anthranilic acid, is termed as anthranilate.

Structure

Anthranilic acid is structurally an amino acid, even though it's seldom recognized as one. In its solid form, anthranilic acid can be found both as an amino-carboxylic acid and in its zwitterionic form, the ammonium carboxylate.

Production

Anthranilic acid's production has been documented through various methods. The industrial production primarily starts from phthalic anhydride, initiated with amination:

C6H4(CO)2O + NH3 + NaOH → C6H4(C(O)NH2)CO2Na + H2O

The sodium salt produced from phthalamic acid undergoes decarbonylation through a Hofmann rearrangement of the amide group, facilitated by hypochlorite:

C6H4(C(O)NH2)CO2Na + HOCl → C6H4NH2CO2H + NaCl + CO2

Another approach involves treating phthalimide with sodium hypobromite in an aqueous sodium hydroxide solution, followed by a neutralization process. Historically, when indigo dye was plant-derived, anthranilic acid was produced as a degradation product of indigo.

Biosynthesis

Anthranilic acid originates from chorismic acid in its biosynthetic pathway. It acts as a precursor to the amino acid tryptophan through the attachment of phosphoribosyl pyrophosphate to its amine group.

Uses

The industrial application of anthranilic acid primarily lies in its role as an intermediate in the synthesis of azo dyes and saccharin. Anthranilic acid and its esters are employed to replicate the fragrances of jasmine and orange in perfumery. Additionally, it finds its use in the pharmaceutical sector, particularly in the manufacture of loop diuretics like furosemide. It's also utilized as a UV-absorber, metal corrosion inhibitor, and mold inhibitor, especially in soy sauce.

In the realm of organic synthesis, anthranilic acid can generate benzyne.

Due to its potential in producing the euphoric sedative drug methaqualone (known commercially as Quaalude or Mandrax), it's listed as a DEA List I Chemical.

Moreover, research suggests that esters derived from anthranilic acid could potentially replace DEET as efficient insect repellents.

See Also

• Aromatic compounds
• Carboxylic acid
• Amine
• Azo dyes
• Saccharin
• Tryptophan