2-Naphthol

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2-Naphthol
Beta-Naphthol.svg
2-Naphthol-3D-balls.png
Names
IUPAC name
Naphthalen-2-ol
Other names
2-Hydroxynaphthalene; 2-Naphthalenol; beta-Naphthol; Naphth-2-ol
Identifiers
135-19-3 YesY
ChEBI CHEBI:10432 YesY
ChEMBL ChEMBL14126 YesY
ChemSpider 8341 YesY
Jmol 3D model Interactive image
Interactive image
KEGG C11713 YesY
PubChem 8663
UNII P2Z71CIK5H YesY
Properties
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)
0.74 g/L
Acidity (pKa) 9.51
Hazards
Main hazards Harmful when inhaled or swallowed; dangerous to environment, esp. aquatic organisms.[1]
R-phrases R20 R22 R50
S-phrases S24 S25 S61
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 161 °C (322 °F)[1]
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 (or occasionally yellow) 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[edit]

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

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.[2]

Applications[edit]

Dyes[edit]

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.[3] Sudan dyes I -IV and Sudan Red G consist of arylazo-substituted naphthols.

Precursor to BINOL[edit]

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[edit]

Naphthols (both 1 and 2 isomers) are used as biomarkers for livestock and humans exposed to polycyclic aromatic hydrocarbons.[4]

References[edit]

  1. ^ a b Safety data for 2-naphthol
  2. ^ a b Gerald Booth "Naphthalene Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a17_009.
  3. ^ Booth, Gerald (2000). Dyes, General Survey. Wiley-VCH. doi:10.1002/14356007.a09_073. 
  4. ^ Sreekanth, R.; Prasanthkumar, Kavanal P.; Sunil Paul, M. M.; Aravind, Usha K.; Aravindakumar, C. T. (7 November 2013). "Oxidation Reactions of 1- and 2-Naphthols: An Experimental and Theoretical Study". The Journal of Physical Chemistry A 117 (44): 11261–11270. doi:10.1021/jp4081355. PMID 24093754. 

External links[edit]