2-Naphthol

2-Naphthol

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Names
IUPAC name Naphthalen-2-ol
Other names 2-Hydroxynaphthalene; 2-Naphthalenol; beta-Naphthol; Naphth-2-ol
Identifiers
CAS Number	135-19-3 Y
ChEBI	CHEBI:10432 Y
ChEMBL	ChEMBL14126 Y
ChemSpider	8341 Y
Jmol 3D model	Interactive image Interactive image
KEGG	C11713 Y
PubChem	8663
UNII	P2Z71CIK5H Y
InChI InChI=1S/C10H8O/c11-10-6-5-8-3-1-2-4-9(8)7-10/h1-7,11H Y Key: JWAZRIHNYRIHIV-UHFFFAOYSA-N Y InChI=1/C10H8O/c11-10-6-5-8-3-1-2-4-9(8)7-10/h1-7,11H Key: JWAZRIHNYRIHIV-UHFFFAOYAV
SMILES Oc2ccc1c(cccc1)c2 c1ccc2cc(ccc2c1)O
Properties
Chemical formula	C10H8O
Molar mass	144.17 g·mol−1
Appearance	Colorless crystalline solid
Density	1.280 g/cm3
Melting point	121 to 123 °C (250 to 253 °F; 394 to 396 K)
Boiling point	285 °C (545 °F; 558 K)
Solubility in water	0.74 g/L
Acidity (pKa)	9.51
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

2-Naphthol, or β-naphthol, is a fluorescent colorless crystalline solid with the formula C₁₀H₇OH. It is an isomer of 1-naphthol, differing by the location of the hydroxyl group on the naphthalene ring. The naphthols are naphthalene homologues of phenol, but more reactive. Both isomers are soluble in simple alcohols, ethers, and chloroform. 2-Naphthol is a widely used intermediate for the production of dyes and other compounds.

Production

Traditionally, 2-naphthol is produced by a two-step process that begins with the sulfonation of naphthalene in sulfuric acid:

C₁₀H₈ + H₂SO₄ → C₁₀H₇SO₃H + H₂O

The sulfonic acid group is then cleaved in molten sodium hydroxide:

C₁₀H₇(SO₃H) + 3 NaOH → C₁₀H₇ONa + Na₂SO₃ + 2 H₂O

Neutralization of the product with acid gives 2-naphthol.

2-Naphthol can also be produced by a method analogous to the cumene process.

Applications

Dyes

The Sudan dyes are popular dyes noted for being soluble in organic solvents. Several of the Sudan dyes are derived from 2-naphthol by coupling with diazonium salts. Sudan dyes I -IV and Sudan Red G consist of arylazo-substituted naphthols.

• Selected 2-Naphthol-derived dyes
• 

  Sudan I

• 

  Sudan II

• Sudan III.svg

  Sudan III

• Sudan IV.svg

  Sudan IV

Precursor to BINOL

They can be also used in the production of dyes and in organic synthesis. For example, 2-naphthol reacts to form BINOL.

Coupling of beta-naphthol using CuCl2

Safety

Naphthols (both 1 and 2 isomers) are used as biomarkers for livestock and humans exposed to polycyclic aromatic hydrocarbons.

External links

• NIST Chemistry WebBook 2-Naphthalenol