2-Naphthol, also known as β-naphthol, acetonaphthol or 2-hydroxynaphthalene, is white shiny flakes or white powder. The density is 1.28g/cm3. The melting point is 123～124℃, the boiling point is 285～286℃, and the flash point is 161℃. It is flammable, and the color will become darker after long-term storage. Sublimation by heating, pungent odor. Insoluble in water, soluble in organic solvents and alkaline solutions.

2. Application in the dye and pigment industry
Dyestuffs and pigment intermediates are the largest consumption area of ​​2-naphthol in my country. The important reason is that the production of dye intermediates has been transferred worldwide, such as 2, 3 acid, J acid, gamma acid, R acid, chromophenol AS These are my country’s important intermediate export products, and the export volume accounts for more than half of the total domestic output. In addition to the synthesis of dyes and pigment intermediates, 2-naphthol can also be used as an azo moiety to react with diazonium compounds to prepare dyes

1, 2, 3 acid
2,3 acid chemical name: 2-hydroxy-3-naphthoic acid, its synthesis method is: 2-naphthol reacts with sodium hydroxide, dehydrated under reduced pressure to obtain sodium 2-naphtholate, and then react with CO2 to obtain 2-naphthalene Phenol and 2,3 sodium salt, remove 2-naphthol and acidify to obtain 2,3 acid. At present, its synthesis methods mainly include solid-phase method and solvent method, and the current solvent method is a major development trend.
Lake pigments with 2,3 acids as coupling components. The synthesis method of this type of pigments is to first make diazonium components into diazonium salts, couple with 2,3 acids, and then use alkali metal and alkaline earth metal salts to combine It is converted into insoluble lake dyes. The main color spectrum of 2,3 acid lake pigment is red light. Such as: C.I. Pigment Red 57:1, C.I. Pigment Red 48:1 and so on.
2,3 acids are widely used in the synthesis of naphthol series ice dyes. In the 1992 “Dyestuff Index”, there are 28 naphthas synthesized with 2,3 acids.
Naphthol AS series are azo pigments with coupling components. The synthesis method of this type of pigment is to first make diazonium components into diazonium salts and couple them with naphthol AS series derivatives, such as on the aromatic ring of the diazonium component. Contains only alkyl, halogen, nitro, alkoxy and other groups, then after the reaction, the common naphthol AS series is the coupling component of the azo pigment, such as the aromatic ring of the diazo component also contains a sulfonic acid group , Coupling with Naphthol AS series derivatives, and then using alkali metal and alkaline earth metal salts to convert it into insoluble lake dyes.
Suzhou Lintong Dyestuff Chemical Co., Ltd. began to produce 2,3 acid in the 1980s. After years of development, it has become the largest domestic and internationally renowned manufacturer of 2,3 acid.

2. Tobias acid
Tobias acid chemical name: 2-aminonaphthalene-1-sulfonic acid. The synthesis method is as follows: 2-naphthol sulfonation to obtain 2-naphthol-1-sulfonic acid, the ammoniation to obtain 2-naphthylamine-1-sodium sulfonate, and acid precipitation to obtain Tobic acid. The sulfonated Tobic acid is sulfonated to obtain the sulfonated Tobic acid (2-naphthylamine-1,5-disulfonic acid).
Tobias acid and its derivatives can be used to produce dyes such as Chromol AS-SW, Reactive Red K1613, Lithol Scarlet, Reactive Brilliant Red K10B, Reactive Brilliant Red K10B, Reactive Brilliant KE-7B, and pigments such as Organic Violet Red

3. J acid
Chemical name of J acid: 2-Amino-5-naphthol-7-sulfonic acid, its synthesis method is: Toubic acid is sulfonated at high and low temperature, hydrolyzed and salted out in acidic medium to obtain 2-naphthylamine-5,72 Sulfonic acid, then neutralization, alkali fusion, acidification to obtain J acid. J acid reacts to obtain J acid derivatives such as N-aryl J acid, bis J acid, and scarlet acid.
J acid and its derivatives can produce a variety of acidic or direct dyes, reactive and reactive dyes, such as: Acid Violet 2R, Weak Acid Purple P-L, Direct Pink, Direct Pink Purple NGB, etc.

4. G salt
G salt chemical name: 2-naphthol-6,8-disulfonic acid dipotassium salt. Its synthesis method is: 2-naphthol sulfonation and salting out. G salt can also be melted, alkali fused, neutralized, and salted out to obtain dihydroxy G salt.
G salt and its derivatives can be used to produce acid dye intermediates, such as acid orange G, acid scarlet GR, weak acid scarlet FG, etc.

5. R salt
R salt chemical name: 2-naphthol-3,6-disulfonic acid disodium salt, its synthesis method is: 2-naphthol sulfonation, salting out. G salt can also be melted, alkali fused, neutralized, and salted out to obtain dihydroxy R salt.
R salt and derivatives can be manufactured: Direct Light Fast Blue 2RLL, Reactive Red KN-5B, Reactive Red Violet KN-2R, etc.

6, 1,2,4 acid
1,2,4 acid chemical name: 1-amino-2-naphthol-4-sulfonic acid, its synthesis method is: 2-naphthol is dissolved in sodium hydroxide, nitrosated with sodium nitrite, and then mixed with excess sodium sulfite Reaction, and finally acidification and isolation to obtain the product. 1,2,4 acid diazotization to obtain 1,2,4 acid oxide body.
1,2,4 acids and derivatives can be used for: acid mordant black T, acid mordant black R, etc.

7. Chevron acid
The chemical name of Chevroic acid: 2-naphthol-6-sulfonic acid, and its synthesis method is: 2-naphthol sulfonation and salting out.
Chevroic acid can be used to make acid dyes and food dye sunset yellow.

8, gamma acid
Gamma acid chemical name: 2-amino-8-naphthol-6-sulfonic acid, its synthesis method is: G salt can also be obtained by melting, alkali melting, neutralization, ammoniating, and acid precipitation.
Gamma acid can be used to make direct black L-N, direct fast tan GF, direct fast ash GF and so on.

9. Application as a coupling part
The synthesis method of this kind of pigment is to first make the diazonium component into a diazonium salt and couple it with β-naphthol. For example, the aromatic ring of the diazonium component contains only alkyl, halogen, nitro, alkoxy and other groups. After the reaction, the ordinary β-naphthol azo pigment is obtained. For example, the aromatic ring of the diazo component also contains a sulfonic acid group, which is coupled with β-naphthol, and then the alkali metal and alkaline earth metal salts can be used to convert it Converted into insoluble lake dyes.
β-naphthol azo pigments are mainly red and orange pigments. Such as C.I. Pigment Red 1,3,4,6 and C.I. Pigment Orange 2,5. The main color spectrum of β-naphthol lake pigment is yellow light red or blue red, mainly including C.I. Pigment Red 49, C.I. Pigment Orange 17, etc.

3. Application in the perfume industry
The ethers of 2-naphthol have the scent of orange blossom and locust blossom, with a softer scent, and can be used as a fixative for soap, toilet water and other essences and some spices. Moreover, they have a higher boiling point and a lower volatility, so the fragrance preservation effect is better.
The ethers of 2-naphthol, including methyl ether, ethyl ether, butyl ether and benzyl ether, can be obtained by the reaction of 2-naphthol and corresponding alcohols under the action of acid catalysts, or 2-naphthol and corresponding sulfate esters or Derived from the reaction of halogenated hydrocarbons.

4. Application in medicine
2-Naphthol also has a wide range of applications in the pharmaceutical industry, and can be used as a raw material for the following drugs or intermediates.
1. Naproxen
Naproxen is an antipyretic, analgesic and anti-inflammatory drug.
The synthesis method of naproxen is as follows: 2-naphthol is methylated and acetylated to obtain 2-methoxy-6-naphthophenone. 2-Methoxy-6-naphthalene ethyl ketone is brominated, ketalized, rearranged, hydrolyzed, and acidified to obtain naproxen.

2. Naphthol caprylate
Naphthol octanoate can be used as a reagent for rapid detection of Salmonella. The synthesis method of naphthol octanoate is obtained by the reaction of octanoyl chloride and 2-naphthol.

3. Pamoic acid
Pamoic acid is a kind of pharmaceutical intermediate, used to prepare such as triptorelin pamoate, pyrantel pamoate, octotel pamoate and so on.
The synthesis method of pamoic acid is as follows: 2-naphthol prepares 2,3 acid, 2,3 acid and formaldehyde are reacted under the catalysis of acid to condense pamoic acid to obtain pamoic acid.
Five, agricultural applications
2-Naphthol can also be used in agriculture to manufacture herbicide naprolamine, plant growth regulator 2-naphthoxyacetic acid and so on.

1. Naprotamine
Naprolamine chemical name: 2-(2-naphthyloxy) propionyl propylamine, which is the first plant hormone-type herbicide containing naphthyloxy to be developed. It has the following advantages: good weeding effect, broad weed-killing spectrum, safety to humans, livestock and aquatic animals, and long validity period. At present, it has been widely used in Japan, South Korea, Taiwan, Southeast Asia and other countries and regions.
The synthesis method of naphthylamine is: α-chloropropionyl chloride reacts with aniline to form α-chloropropionylanilide, which is then obtained by condensation with 2-naphthol.

2. 2-Naphthoxyacetic acid
2-Naphthoxyacetic acid is a new type of plant growth regulator, which has the functions of preventing flower and fruit falling, increasing yield, improving quality and premature maturity. It is mainly used to regulate the growth of pineapple, apple, tomato and other plants and increase the yield rate.
The synthesis method of 2-naphthoxyacetic acid is: halogenated acetic acid and 2-naphthol are condensed under alkaline conditions, and then obtained by acidification.

6. Application in the polymer material industry

1, 2, 6 acid

2,6 acid chemical name: 2-hydroxy-6-naphthoic acid, its synthesis method is: 2-naphthol reacts with potassium hydroxide, dehydrated under reduced pressure to obtain potassium 2-naphthol, and then react with CO2 to obtain 2-naphthalene Phenol and 2,6 acid potassium salt, remove 2-naphthol and acidify to obtain 2,6 acid. At present, its synthesis methods mainly include solid-phase method and solvent method, and the current solvent method is a major development trend.
2,6 acid is an important organic intermediate for engineering plastics, organic pigments, liquid crystal materials, and medicine, especially as a monomer for temperature-resistant synthetic materials. High temperature resistant polymers produced with 2,6 acid as raw materials are widely used in the liquid crystal material industry.
Suzhou Lintong Dyestuff Chemical Co., Ltd. has developed polymer-grade 2,6 acid based on the technology of 2,3 acid, and its output has gradually expanded. At present, 2,6 acid has become one of the company’s main products.

2. 2-Naphthylthiol

2-Naphthylthiol can be used as a plasticizer when masticating rubber in an open mill, which can improve the effect of mastication, shorten mastication time, save electricity, reduce elastic recovery, and reduce rubber shrinkage. It can also be used as intersecting regeneration activator and antioxidant.
The synthesis method of 2-naphthylthiol is as follows: 2-naphthol is reacted with dimethylaminothioformyl chloride, then heated and obtained by acidic hydrolysis.

3. Rubber antioxidant

3.1 Anti-aging agent D
Anti-aging agent D, also known as anti-aging agent D, chemical name: N-phenyl-2-naphthylamine. A general-purpose antioxidant for natural rubber and synthetic rubber, used in the manufacture of industrial products such as tires, tapes, and rubber shoes.
The synthesis method of antioxidant D is: 2-naphthol pressurized ammonolysis to obtain 2-naphthylamine, which is then obtained by condensation with halogenated benzene.

3.2. Anti-aging agent DNP
Anti-aging agent DNP, chemical name: N, N-(β-naphthyl) p-phenylenediamine, is a chain break terminating type anti-aging agent and metal complexing agent. It is mainly used as an anti-aging agent for nylon and nylon tire cords, wire and cable insulation rubbers that contact copper cores, and other rubber products.
The synthesis method of anti-aging agent DNP is: p-phenylenediamine and 2-naphthol heating and shrinking table

4. Phenolic and epoxy resin
Phenolic and epoxy resins are commonly used engineering materials in the industry. Studies have shown that phenolic and epoxy resins obtained by replacing or partially replacing phenol with 2-naphthol have higher heat resistance and water resistance.