p-Aminobenzoic Acid
Title: p-Aminobenzoic Acid
CAS Registry Number: 150-13-0
CAS Name: 4-Aminobenzoic acid
Additional Names: vitamin Bx; bacterial vitamin H1; chromotrichia factor; anti-chromotrichia factor; trichochromogenic factor; anticanitic vitamin; PABA
Trademarks: Pabanol (Valeant)
Molecular Formula: C7H7NO2
Molecular Weight: 137.14
Percent Composition: C 61.31%, H 5.14%, N 10.21%, O 23.33%
Literature References: Widely distributed in nature as a B complex factor. Baker's yeast contains 5 to 6 ppm, brewer's yeast from 10 to 100 ppm. Occurs free and in ester form. Prepn: Toland, Heaton, US 2878281 (1959 to Calif. Research Corp.); Spiegler, US 2947781 (1960 to Du Pont); Nielson et al., J. Chem. Soc. 1962, 371. Purification: Lyding, US 2735865 (1956 to Heyden Chem.). Antirickettsial activity: M. L. Robbins et al., J. Immunol. 64, 431 (1950). Toxicity studies: C. C. Scott, E. B. Robbins, Proc. Soc. Exp. Biol. Med. 49, 184 (1942); R. K. Richards, Fed. Proc. 1, 71 (1942); G. Cronheim, ibid. 10, 289 (1952). Comprehensive description: H. A. El-Obeid, A. A. Al-Badr, Anal. Profiles Drug Subs. Excip. 22, 33-106 (1993).
Properties: Monoclinic prisms from dil alcohol. May turn slightly yellow on prolonged exposure to light and air. mp 187.0-187.5°. pKa: 4.65, 4.80; pH (0.5% soln): 3.5. uv max (water): 266 nm (E1%1cm 1070); (isopropanol): 288 nm (E1%1cm 137). One gram dissolves in 170 ml water at 25°, in 90 ml boiling water; in 8 ml alcohol, in 50 ml ether. Sol in ethyl acetate, glacial acetic acid; slightly sol in benzene. Practically insol in petr ether. Incompatible with ferric salts and oxidizing agents. LD50 in mice, rats (g/kg): 2.85, >6.0 orally (Scott, Robbins). LD50 in rabbits (g/kg): 2.0 i.v. (Richards); 1.83 orally (Cronheim).
Melting point: mp 187.0-187.5°
pKa: pKa: 4.65, 4.80; pH (0.5% soln): 3.5
Absorption maximum: uv max (water): 266 nm (E1%1cm 1070); (isopropanol): 288 nm (E1%1cm 137)
Toxicity data: LD50 in mice, rats (g/kg): 2.85, >6.0 orally (Scott, Robbins); LD50 in rabbits (g/kg): 2.0 i.v. (Richards); 1.83 orally (Cronheim)
 
Derivative Type: Diethylamine salt
CAS Registry Number: 6018-84-4
Molecular Formula: C11H18N2O2
Molecular Weight: 210.27
Percent Composition: C 62.83%, H 8.63%, N 13.32%, O 15.22%
Properties: Crystals from acetone mp 170-173°. Very soluble in water.
Melting point: mp 170-173°
 
Derivative Type: Potassium salt see Potassium p-Aminobenzoate
 
NOTE: p-Aminobenzoic acid is also known as anti-gray-hair factor (in rats only).
Use: Manuf various esters (local anesthetics), folic acid, and azo dyes; in sunburn preventives. Used in laboratories as sulfonamide antagonist.
Therap-Cat: Ultraviolet screen. Formerly as antirickettsial.
Therap-Cat-Vet: Has been used in eczema nasi ("collie nose") in dogs.
Keywords: Antirickettsial; Ultraviolet Screen.

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