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4-Aminobenzoic acid

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4-Aminobenzoic acid Basic information
4-Aminobenzoic acid Chemical Properties
  • Melting point:187-189 °C(lit.)
  • Boiling point:251.96°C (rough estimate)
  • Density 1.374 g/mL at 25 °C(lit.)
  • refractive index 1.5323 (estimate)
  • Flash point:250 °C
  • storage temp. 2-8°C
  • solubility 95% ethanol: soluble5%, clear to slightly hazy, colorless to yellow
  • form Crystalline Powder
  • pka2.50, 4.87(at 25℃)
  • color White to light yellow
  • PH3.5 (5g/l, H2O, 20℃)
  • OdorOdorless
  • PH Range3.5
  • Water Solubility 4.7 g/L (20 ºC)
  • Sensitive Air & Light Sensitive
  • Merck 14,423
  • BRN 471605
  • Stability:Stable. Incompatible with strong oxidizing agents. Combustible. Sensitive to light and air. May discolour on exposure to light.
  • CAS DataBase Reference150-13-0(CAS DataBase Reference)
  • NIST Chemistry Referencep-Aminobenzoic acid(150-13-0)
  • IARC3 (Vol. 16, Sup 7) 1987
  • EPA Substance Registry Systemp-Aminobenzoic acid (150-13-0)
Safety Information
  • Hazard Codes Xn,Xi
  • Risk Statements 22-36/37/38-43
  • Safety Statements 26-36-37/39
  • WGK Germany 3
  • RTECS DG1400000
  • TSCA Yes
  • HS Code 29224995
  • Hazardous Substances Data150-13-0(Hazardous Substances Data)
  • ToxicityLD50 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)
4-Aminobenzoic acid Usage And Synthesis
  • Description4-Aminobenzoic acid (also known as para-aminobenzoic acid or PABA because the number 4 carbon in the benzene ring is also known as the para position) is an organic compound with the formula H2NC6H4CO2H. PABA is a white solid, although commercial samples can appear gray. It is slightly soluble in water. It consists of a benzene ring substituted with amino and a carboxyl groups. The compound occurs naturally. The potassium salt is used as a drug against fibrotic skin disorders, such as Peyronie's disease, under the trade name Potaba. PABA is also occasionally used in pill form by sufferers of irritable bowel syndrome to treat its associated gastrointestinal symptoms, and in nutritional epidemiological studies to assess the completeness of 24-hour urine collection for the determination of urinary sodium, potassium, or nitrogen levels.
  • Chemical PropertiesWhite to off white crystalline powder
  • OriginatorPabalate,Robins,US,1949
  • Usesoctyl dimethyl PABA (padimate-O; p-aminobenzoic acid) is an FDA-approved sunscreen chemical whose InCI name is now ethylhexyl dimethyl PABA.
    gastric acid secretion inhibitor
  • UsesPABA is a sunscreen chemical with an approved usage level of 5 to 15 percent. It is found to be irritating to sensitive skin, has the potential to cause sensitization, and is considered too water soluble. once extremely popular, this ingredient has practically disappeared from sunscreen formulations. PABA is a yellowish or colorless acid found in vitamin B complex.
  • UsesWidely 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.
  • Uses4-aminobenzoic acid is an aminobenzoic acid isomer that combines with pteridine and glutamic acid to folic acid. The fact that 4-aminobenzoic acid absorbs light throughout the UVB range has also resulted in its use as an ingredient in sunscreens. Also it is used as a component of some medicines e.g analgesic or anesthetic preparations sunscreen agents and bentiromide.
  • DefinitionChEBI: An aminobenzoic acid in which the amino group is para to the carboxy group.
  • IndicationsPABA preparations absorb UVL between 280 and 320 nm. This acid will stain white fabrics, especially cotton. The esters of PABA are slightly less effective and do not stain as much. Cross-sensitization can occur with some sunscreens. In particular, PABA and its derivatives may cross-react with sulfonamides, benzocaine, procaine, paraphenylenediamine, and azo dyes. Padimate-O, the ester form of PABA, is also used for UVB protection.
  • Manufacturing ProcessThe following example illustrates in detail the preparation of amino benzoic acids from the hot reaction product obtained by the oxidation of a xylene and containing a mixture of salt, amide salt and diamide of a phthalic acid.
    800 cc of hot aqueous oxidation product, obtained from the oxidation of pxylene with ammonium sulfate, hydrogen sulfide and water are boiled and agitated for 4 hours to remove carbon dioxide, hydrogen sulfide and ammonia, sufficient water being added to maintain a constant volume. The mixture is filtered to remove a precipitate containing elemental sulfur. 12 grams of activated charcoal are added to the filtrate and the mixture held at a temperature of 180°F for 20 minutes. Filtration through diatomaceous earth removes color bodies formed during the oxidation process and yields a pale yellow filtrate. The filtrate is acidified with sulfuric acid to a pH of 3 or less to precipitate approximately 49 grams of white solid, comprising a mixture of terephthalic acid and amides of terephthalic acid, which are removed by filtration. This solid is then washed with water at 200°F and redissolved in 200 cc of water containing 28.6 grams of sodium hydroxide.
    A mixture of sodium hypochlorite and sodium hydroxide is prepared by adding 27.5 grams of chlorine to a vessel equipped with cooling means and containing a solution of 50 grams of sodium hydroxide in 375 cc of water, thereafter adding sufficient water to produce 500 cc of solution. 190 cc of this cold solution are slowly added to the acid-amide solution previously prepared so as to keep the temperature of the mixture below 55°F. The mixture is stirred for 15 minutes and then heated rapidly to 200°F and maintained at that temperature for one hour. 2 grams of sodium thiosulfate are added to consume excess sodium hypochlorite. The solution is acidified to a pH of 3 or less and filtered hot. The filter cake, comprising about 26.9 grams of terephthalic acid, is then suspended in 300 cc of dilute sulfuric acid of pH about 2, heated to 200°F and filtered hot.
    The filtrates are combined, cooled, and extracted with three successive 200 cc portions of ether. The pH of the filtrate is then raised to 3.5 with sodium hydroxide and the filtrate extracted with six successive 200 cc portions of ether to yield the balance of the product. The crude p-aminobenzoic acid product is recovered by evaporation of ether and is suspended in hot benzene, cooled and filtered to remove benzoic and toluic acids together with small amounts of impurities soluble in the filtrate. Recrystallization of the product from 200 cc of water yields 14.5 grams of light tan needles of p-aminobenzoic acid having an acid number of 411 (theoretical value 409).
    Aminobenzoic acid can be then purified and decolorized by a process described in US Patent 2,735,865.
  • brand nameRVPaba Lipstick (ICN).
  • Therapeutic FunctionSunscreen agent, Antirickettsial
  • Synthesis Reference(s)Synthesis, p. 285, 1971
    Tetrahedron, 47, p. 8587, 1991 DOI: 10.1016/S0040-4020(01)82402-9
  • General DescriptionColorless crystals that discolor on exposure to light and air.
  • Reactivity Profile4-Aminobenzoic acid is incompatible with ferric salts and oxidizing agents.
  • HazardQuestionable carcinogen.
  • Safety ProfileModerately toxic by ingestion and intravenous routes. Ingesting large doses can cause nausea, vomiting, skin rash, methemoglobinemia, and possibly toxic hepatitis. Experimental reproductive effects. Mutation data reported. Questionable carcinogen. Combustible. When heated to decomposition it emits toxic fumes of NO,. A topical sunscreen.
  • Purification MethodsPurify p-aminobenzoic acid by dissolving it in 4-5% aqueous HCl at 50-60o, decolorising with charcoal and carefully precipitating it with 30% Na2CO3 to pH 3.5-4 in the presence of ascorbic acid. It can be recrystallised from water, EtOH or EtOH/water mixtures. [Beilstein 14 IV 1126.]
4-Aminobenzoic acid Preparation Products And Raw materials
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