p -aminobenzoic acid

Structural formula
General
Surname	p -aminobenzoic acid
other names	para- aminobenzoic acid 4-aminobenzoic acid ( IUPAC ) p -carboxyaniline PABA ( INCI )
Molecular formula	C 7 H 7 NO 2
Brief description	light yellow, odorless solid
External identifiers / databases
CAS number 150-13-0 EC number 205-753-0 ECHA InfoCard 100.005.231 PubChem 978 ChemSpider 953 DrugBank DB02362 Wikidata Q284959
Drug information
ATC code	D02 BA01
properties
Molar mass	137.14 g mol −1
Physical state	firmly
density	1.38 g cm −3 (20 ° C)
Melting point	188.5 ° C
Vapor pressure	37.06 m Pa (25 ° C)
pK s value	2.38
solubility	poor in water (6.11 g l −1 at 30 ° C)
safety instructions
Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed GHS labeling of hazardous substances Caution H and P phrases H: 315-319-335 P: 261-280-304 + 340-305 + 351 + 338-405-501
Toxicological data	2850 mg kg −1 ( LD 50 ,  mouse ,  oral ) 1000 mg kg −1 ( LD 50 ,  dog ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

p- Aminobenzoic acid ( PABA ) is an organic carboxylic acid , a component of folic acid and is often assigned to the B vitamins , but is not a vitamin . For many bacteria it is an important growth substance that is needed to produce folic acid. This process can bedisruptedby the similarly structured sulfonamides . These compounds used as medicines act as antimetabolites , prevent the production of folic acid and thereby limit the reproduction of bacteria. In addition to p -aminobenzoic acid (4-aminobenzoic acid), there are two further positionally isomeric forms, namely anthranilic acid (2-aminobenzoic acid) and 3-aminobenzoic acid .

properties

p -Aminobenzoic acid forms colorless crystals that are soluble in hot water, ethanol, ether, glacial acetic acid. It is easily oxidized, e.g. B. with iron (III) salts; slightly yellowish-red discoloration occurs in air or under the influence of light. Bacteria, plants and fungi need p- aminobenzoic acid as a vital growth substance for the synthesis of folic acid by dihydropteroate synthase . Baker's yeast contains approx. 5–10 ppm p -aminobenzoic acid. The biosynthesis takes place from chorismic acid and glutamate .

use

Used as a starting material for the synthesis of azo dyes , folic acid , local anesthetics and as a UV absorber (UV-B filter) in sunscreens (maximum 5% allowed). In addition, p- aminobenzoic acid is sold as a dietary supplement under the name PABA.

toxicology

p -aminobenzoic acid shows low acute toxicity ; no indications of carcinogenicity were found. Sensitization experiments on guinea pigs did not provide any evidence of a sensitizing effect. p- Aminobenzoic acid is hardly absorbed through the skin. After ingestion, the main metabolites are p- aminohippuric acid (PAH) and p -acetylaminohippuric acid (4-acetamidohippuric acid, PAAHA).

Derivatives

• Benzocaine (ethyl ester)
• Cycloform (isobutyl ester)
• Procaine (2- ( N , N -diethylamino) ethyl ester)

Web links

• deutschlandradio.de: Meal! Conversations with Udo Pollmer - Beauty Vitamins , November 16, 2002.
• Beilstein's Handbook of Organic Chemistry : 14 , E1

Individual evidence

1. ^ Entry on PABA in the CosIng database of the EU Commission, accessed on March 21, 2020.
2. ↑ ^{a b c d} Entry on 4-aminobenzoic acid in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
3. ↑ ^{a b c d e} Entry on p-aminobenzoic acid in the ChemIDplus database of the United States National Library of Medicine (NLM), accessed on July 31, 2018 or earlier.
4. ↑ CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .
5. ↑ https://eur-lex.europa.eu/legal-content/DE/TXT/PDF/?uri=CELEX:32009R1223&from=DE
6. ↑ Entry on 4-aminobenzoic acid. In: Römpp Online . Georg Thieme Verlag, accessed on February 2, 2019.