4-Aminobenzoic acid
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| 4-Aminobenzoic acid | |
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| General | |
| Systematic name | 4-Aminobenzoic acid |
| Other names | para-Aminobenzoic acid p-Aminobenzoic acid PABA Vitamin Bx Bacterial vitamin H1 |
| Molecular formula | C7H7NO2 |
| SMILES | C1=CC(=CC=C1C(=O)O)N |
| Molar mass | 137.136 g/mol |
| Appearance | white crystals |
| CAS number | [150-13-0] |
| Properties | |
| Density and phase | 1.374 g/ml, ? |
| Solubility in water | 1 g/170 ml (25 °C) 1 g/90 mL (90 °C) |
| Melting point | 187-189 °C |
| Boiling point | ? °C |
| Acidity (pKa) | 4.65 |
| Basicity (pKb) | 9.35 |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | ? |
| NFPA 704 | |
| Flash point | ? °C |
| R/S statement | R: ? S: ? |
| RTECS number | ? |
| Related compounds | |
| Related compounds | aniline benzoic acid |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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4-Aminobenzoic acid (also known as para-aminobenzoic acid or PABA) is an organic compound with the molecular formula C7H7NO2. PABA is a white crystalline substance that is only slightly soluble in water. It consists of a benzene ring substituted with an amino group and a carboxylic acid.
PABA is an essential nutrient for some bacteria and is sometimes called Vitamin Bx[citation needed]. However, PABA is not essential to human health, and is therefore not officially classified as a vitamin. Although humans lack the ability to synthesize folate from PABA, it is sometimes marketed as an essential nutrient under the premise that it can stimulate intestinal bacteria.
PABA is an intermediate in bacterial synthesis of folate. Sulfonamides are chemically similar to PABA, and their antibacterial activity is due to their ability to interfere with conversion of PABA to folate, and subsequent utilization, by bacteria.
In the past, PABA has been widely used as a UV filter in sunscreen formulations. However, it has been determined that it increases the formation of a particular DNA defect in human cells, thus increasing the risk of skin cancer in people who lack the mechanisms to repair these cellular defects.[1] Currently, safer and more effective derivatives of PABA, such as octyl dimethyl PABA, are more commonly used.
The potassium salt is used as a drug against fibrotic skin disorders under the trade name POTABA.[2] PABA is also occasionally used in pill form by sufferers of Irritable bowel syndrome to treat the associated gastrointestinal symptoms.
PABA also finds use in the manufacture of esters, folic acid, and azo dyes.
[edit] In popular culture
It was discussed in The Lip Reader which is an episode of Seinfeld.
- George: ... This has PABA in it, I need PABA-free.
Jerry: You got a problem with PABA?
George: Yes, I have a problem with PABA.
Jerry: You don't even know what PABA is.
George: I know enough to stay away from it.
[edit] References
- ^ P. J. Osgood; S. H. Moss, D. J. Davies (1982). "The sensitization of near-ultraviolet radiation killing of mammalian cells by the sunscreen agent para-aminobenzoic acid". Journal of Investigative Dermatology 79 (6): 354-357.
- ^ Compound Summary on PubChem. PubChem. National Institute of Health: National Library of Medicine (2006). Retrieved on April 5, 2006.
