Article: 4-Aminobenzoic acid

4-Aminobenzoic acid
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	? g/cm3, ?
Solubility in water	1 g/170 ml (25 °C) 1 g/90 mL (90 °C)
Melting point	187 °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

4-Aminobenzoic acid, para-aminobenzoic acid, or simply PABA, is an organic compound with 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 B_x. However, PABA is not essential for humans and it varies in its activity from other B vitamins. 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.

Sulfonamides (sulfa drugs) are chemically similar to PABA, and their antibacterial activity is due to their ability to interfere with PABA utilization by bacteria.

In the past, PABA has been widely used as 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 drug against fibrotic skin disorders.^[2]

PABA also finds use in the manufacture of esters, folic acid, and azo dyes.