p -aminobenzoic acid
Structural formula | ||||||||||||||||||||||
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General | ||||||||||||||||||||||
Surname | p -aminobenzoic acid | |||||||||||||||||||||
other names |
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Molecular formula | C 7 H 7 NO 2 | |||||||||||||||||||||
Brief description |
light yellow, odorless solid |
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Drug information | ||||||||||||||||||||||
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properties | ||||||||||||||||||||||
Molar mass | 137.14 g mol −1 | |||||||||||||||||||||
Physical state |
firmly |
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density |
1.38 g cm −3 (20 ° C) |
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Melting point |
188.5 ° C |
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Vapor pressure |
37.06 m Pa (25 ° C) |
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pK s value |
2.38 |
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solubility |
poor in water (6.11 g l −1 at 30 ° C) |
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safety instructions | ||||||||||||||||||||||
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Toxicological data | ||||||||||||||||||||||
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
- ^ Entry on PABA in the CosIng database of the EU Commission, accessed on March 21, 2020.
- ↑ a b c d Entry on 4-aminobenzoic acid in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
- ↑ 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.
- ↑ CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .
- ↑ https://eur-lex.europa.eu/legal-content/DE/TXT/PDF/?uri=CELEX:32009R1223&from=DE
- ↑ Entry on 4-aminobenzoic acid. In: Römpp Online . Georg Thieme Verlag, accessed on February 2, 2019.