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Chemical Properties
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White lustrous leaflets or white powder. Insoluble in water, soluble in ethanol, ether, chloroform, glycerol, and alkaline solutions.
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Application
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It is used to produce Tobias acid, J acid, 2-hydroxy-3-naphthoic acid and azo dyes, and it is the raw material for rubber antioxidants, mineral dressing agents, fungicides, antiseptics, preservatives, etc.
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As feed preservative. In China, it can be used for citrus preservation, the maximum dosage amount is 0.1 g/kg and the residue amount should be no more than 70 mg/kg.
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2-Naphthol, also called ß-naphthol, 2-naphthalenol, is the intermediate for plant growth regulator, 2-naphthoxyacetic acid.
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As analytic agent, absorbent of ethylene and carbon monoxide, and fluorescence indicator.
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Important organic raw material and dye intermediate, used to produce Tobias acid, butyric acid, β-hydroxynaphthoic acid and used to produce N-phenyl-2-naphthylamine, Diafen NN and other antioxidant, organic pigments, and fungicides.
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For the detection of bromine, chlorine, chlorate, niobium, copper, nitrite, and potassium. Substrate for fluorometric assay of phenol sulfotransferase. Acid and alkali indicator, dyes, organic synthesis, qualitative determination of allyl alcohol, methanol, chloroform, etc. Absorbent of carbon monoxide, ethanol, and fluorescence indicator. Determination of carbon monoxide, copper, nitrite, and potassium. Ethylene absorbent.
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Preparation
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(1) Sulfonation alkali melting method
Obtained by sulfonation of naphthalene and alkali melting. Sulfonation alkali melting 2-naphthol synthesis process is widely used in both domestic and foreign production, but it is with serious corrosion, high cost, large amount of waste water and high biological oxygen consumption. American Cyanamid Company developed 2-isopropyl-naphthalene method with naphthalene and propylene as the raw materials, which produces 2-naphthol and with byproduct acetone. This method is similar to Cumene process to produce phenol. The consumed amount of raw materials: 1170 kg/t refined naphthalene, 1080 kg/t sulfuric acid, 700 kg/t sodium hydroxide (caustic soda).
Details: Refined naphthalene was put into the sulfonation kettle and heated up to 140°C (melting). Sulfuric acid (sulfuric acid/refined naphthalene (mol/mol=1.8) was added within 20 minutes. The temperature was raised up to 160-164°C and kept for 2.5 h. The reaction was terminated when the content of 2-naphthalenesulfonic acid is above 66% and the total acidity is 25%-27%. The sulfonates were hydrolyzed for 1 h at 140-150°C inside a hydrolysis kettle. Following neutralization at 80-90°C with sodium nitrite solution was performed until the Congo red test paper was no more blue. Steam and air were used to remove SO2 gas. When the temperature was cooled down to 30-40°C, vacuum filtration was applied. After washing with salt water (10%) and following vacuum filtration, 2-naphthalenesulfonic acid sodium salt was obtained.
Sodium hydroxide was put into an alkali melting kettle and heated to 290°C (melting). At about 3 hours 2-naphthalenesulfonic acid sodium salt was added until the freebase content was 5%-6%. Afterwards, the temperature was kept at 320-330°C for 1 hour. The alkali melt was diluted with water and SO2 gas was passed at 70-80°C until phenolphthalein did not show any color. Addition of water to boil and wash, sodium sulfite was removed, dehydration and then under reduced pressure to distill the final product. The total yield is 73%-74%.
(2) 2-isopropyl-naphthalene method.
With naphthalene and ethylene as the raw materials to produce 2-naphthaol with byproduct acetone.
Details: Sulfuric acid was added into the melted naphthalene at 140ºC and the sulfonation was carried out at 162-164°C. The sulfonates were hydrolyzed, the free naphthalene was blown away and sodium sulfite was added to react and generate 2-naphthalenesulfonic acid sodium salt. This salt together with sodium hydroxide were alkali melted at 285-320°C and kept at 320-330°C for 1 hour. After the dilution of this alkali melt, acidification with SO2 gas was performed to obtain crude products. Followed washing, dehydration and distillation were carried out to obtain the final products.
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Chemical Properties
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white or off-white powder with a slight
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Chemical Properties
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2-Naphthol is a white, crystalline solid. Slight phenolic odor. Darkens in air and on exposure to light.
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Uses
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Has been used as antiseptic, anthelmintic and counter-irritant in alopecia.
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Uses
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anthelmintic, antiseptic
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Uses
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2-Naphthol is used in the manufacture of dyes, perfumes, and medicinal organics, and in the production of antioxidants for synthetic rubber.
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Definition
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ChEBI: A naphthol carrying a hydroxy group at position 2.
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Synthesis Reference(s)
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Journal of the American Chemical Society, 72, p. 4884, 1950
DOI:
10.1021/ja01167a009
Synthesis, p. 437, 1985
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Hazard
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See α-naphthol
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Health Hazard
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Although the toxicity of 2-naphthol is of low order in test animals, ingestion of large amounts may result in nausea, vomiting, diarrhea, abdominal pain, convulsions, and hemolytic anemia. Death may result from respiratory failure. The oral LD50 value in rats is in the range 2000 mg/kg. 2-Naphthol is slightly more toxic than 1-naphthol [9015-3], the oral LD50 value of which is in the range 2500 mg/kg.
Skin contact can produce peeling of the skin and pigmentation.
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Fire Hazard
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Noncombustible solid.
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Safety Profile
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Poison by ingestion, inhalation, and subcutaneous routes. Mutation data reported. A skin and eye irritant. Combustible when exposed to heat or flame. To fight fire, use CO2, dry chemical. Incompatible with antipyrine, camphor, phenol, ferric salts, menthol, potassium permanganate and other oxidzing materials, urethane.
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Potential Exposure
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A potential danger to those involved in rubber antioxidant production, synthesis of dyes; leather processing; fungicides, pharmaceuticals, and perfumes. Used as an antioxidant for fats, oils; as an antiseptic; in insecticides.
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Shipping
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UN2811 Toxic solids, organic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required. UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard Class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required.
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Purification Methods
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Crystallise 2-naphthol from aqueous 25% EtOH (charcoal), H2O, *benzene, toluene or CCl4. Alternatively, extract it repeatedly with small amounts of EtOH, followed by dissolution in a minimum volume of EtOH and precipitation with distilled water, then drying over P2O5 under vacuum. It has also been dissolved in aqueous NaOH and precipitated by adding acid (repeat several times), then precipitated from *benzene by addition of heptane. Final purification can be by zone melting or sublimation in vacuo. The 4-nitrobenzoate has m 104o (from EtOH). [Bardez et al. J Phys Chem 89 5031 1985, Kikuchi et al. J Phys Chem 91 574 1987, Beilstein 6 IV 4253.]
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Incompatibilities
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Dust or powder may form explosive mixture with air. Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides, iron salts; 2,3-dimethyl-1- phenyl-3-pyrazolin-5-one (antipyrine); camphor, phenol, menthol, urethane.
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Waste Disposal
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Mix with flammable solvent and atomize into an incinerator.
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