2-Naphthol

{{chembox

| Watchedfields = changed

| verifiedrevid = 477214746

| ImageFile = Beta-Naphthol.svg

| ImageSize = 180px

| ImageFile1 = 2-Naphthol-3D-balls.png

| ImageSize1 = 180px

| ImageFile2 = Β-Naphthol.jpg

| ImageSize2 = 220px

| PIN=Naphthalen-2-ol

| OtherNames=2-Hydroxynaphthalene; 2-Naphthalenol; beta-Naphthol; Naphth-2-ol

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo=135-19-3

| Beilstein = 742134

| ChEBI_Ref = {{ebicite|correct|EBI}}

| ChEBI = 10432

| ChEMBL_Ref = {{ebicite|correct|EBI}}

| ChEMBL = 14126

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 8341

| EC_number = 205-182-7

| Gmelin = 27395

| KEGG_Ref = {{keggcite|correct|kegg}}

| KEGG = C11713

| PubChem=8663

| RTECS = QL2975000

| UNNumber = 3077

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = P2Z71CIK5H

| SMILES = Oc2ccc1c(cccc1)c2

| InChI = 1/C10H8O/c11-10-6-5-8-3-1-2-4-9(8)7-10/h1-7,11H

| InChIKey = JWAZRIHNYRIHIV-UHFFFAOYAV

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/C10H8O/c11-10-6-5-8-3-1-2-4-9(8)7-10/h1-7,11H

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = JWAZRIHNYRIHIV-UHFFFAOYSA-N

| SMILES1 = c1ccc2cc(ccc2c1)O

}}

|Section2={{Chembox Properties

| C=10 | H=8 | O=1

| Appearance=Colorless crystalline solid

| Density=1.280 g/cm³

| MeltingPtC = 121 to 123

| BoilingPtC = 285

| Solubility=0.74 g/L

| pKa = 9.51

| MagSus = −98.25·10⁻⁶ cm³/mol

}}

|Section3={{Chembox Hazards

| MainHazards= Harmful when inhaled or swallowed; dangerous to environment, esp. aquatic organisms.{{Cite web |title=MSDS safety data for 2-naphthol |url=https://msds.chem.ox.ac.uk/NA/2-naphthol.html |url-status=dead |archive-url=https://web.archive.org/web/20110303133020/https://msds.chem.ox.ac.uk/NA/2-naphthol.html |df=dmy-all |archive-date=2011-03-03}}

| FlashPtC = 161

| FlashPt_ref =

| AutoignitionPtC =

| NFPA-H = 2

| NFPA-F = 1

| NFPA-R = 0

| GHSPictograms = {{GHS07}} {{GHS09}}

| GHSSignalWord = Warning

| HPhrases = {{H-phrases|302|332|400}}

| PPhrases = {{P-phrases|261|264|270|271|273|301+312|304+312|304+340|312|330|391|501}}

}}

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

Traditionally, 2-naphthol is produced by a two-step process that begins with the sulfonation of naphthalene in sulfuric acid:{{Ullmann|first=Gerald|last=Booth|title=Naphthalene Derivatives|year=2005|doi=10.1002/14356007.a17_009}}. [https://pdfslide.net/documents/ullmanns-encyclopedia-of-industrial-chemistry-naphthalene-derivatives.html full-text PDF]

: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-Naphthol-derived 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.{{cite book|last1=Booth|first1=Gerald|first2=Heinrich|last2=Zollinger|first3=Keith|last3=McLaren|first4=William G.|last4=Sharples|first5=Alan|last5=Westwell|year=2000|publisher=Wiley-VCH|doi=10.1002/14356007.a09_073|title=Ullmann's Encyclopedia of Industrial Chemistry|isbn=9783527306732|chapter=Dyes, General Survey}} Sudan dyes I–IV and Sudan Red G consist of arylazo-substituted naphthols.

File:Sudan I.svg|Sudan I

File:Sudan II.svg|Sudan II

File:Sudan III.svg|Sudan III

File:Sudan IV.svg|Sudan IV

File:Oil Red O.svg|Oil Red O

File:Naphthol AS.svg|Naphthol AS

Reactions

Some reactions of 2-naphthol are explicable with reference to its tautomerism, which produces a small amount of the keto tautomer.

:File:Beta-naphthol tautomerism.svg

One consequence of this tautomerism is the Bucherer reaction, the ammonolysis of 2-naphthol to give 2-aminonaphthalene.

2-Naphthol can be oxidatively coupled to form BINOL, a C₂-symmetric ligand popularized for use in asymmetric catalysis.

File:CuCl2 naphthol coupling.png{{clear left}}

2-Naphthol converts to 2-naphthalenethiol by reaction with dimethylthiocarbamoyl chloride via the Newman–Kwart rearrangement.{{cite journal|title=Thiophenols from Phenols: 2-Naphthalenethiol|author1=Melvin S. Newman |author2=Frederick W. Hetzel|url=https://www.orgsyn.org/demo.aspx?prep=CV6P0824 |journal=Organic Syntheses|year=1971|volume=51|page=139|doi=10.15227/orgsyn.051.0139|url-access=subscription}} The OH→Br conversion has been described.{{cite journal |doi=10.15227/orgsyn.049.0006|title=2-Bromonaphthalene |journal=Organic Syntheses |year=1969 |volume=49 |page=6 |author1=J. P. Schaefer|author2=Jerry Higgins|author3=P. K. Shenoy }}

Electrophilic attack occurs characteristically at the 1-position as indicated by nitrosylation to give 1-nitroso-2-naphthol.{{cite journal |doi=10.15227/orgsyn.002.0061|journal=Organic Syntheses |year=1922 |volume=2 |page=61 |title=Nitroso-β-Naphthol |first1=C. S.|last1=Marvel|first2=P. K.| last2=Porter}} Bromination{{cite journal |doi=10.15227/orgsyn.020.0018|title=6-Bromo-2-Naphthol |journal=Organic Syntheses |year=1940 |volume=20 |page=18 |author=C. Frederick Koelsch }} and alkylations proceed with similar regiochemistry.{{cite journal |doi=10.15227/orgsyn.022.0063|title=2-Hydroxy-1-Naphthaldehyde |journal=Organic Syntheses |year=1942 |volume=22 |page=63|author=Alfred Russell Luther B. Lockhart }} Ring-opening reactions have been documented.{{cite journal |doi=10.15227/orgsyn.034.0008 |journal=Organic Syntheses |year=1954 |volume=34 |page=8|title=β-(o-Carboxyphenyl)propionic Acid |author=G. A. Page, D. S. Tarbell }}

Carbonation of 2-naphthol gives 2-hydroxy-1-naphthoic acid.

Safety

2-Naphthol has been described as "moderately toxic.

References

External links

[http://webbook.nist.gov/cgi/cbook.cgi?Name=2-naphthol&Units=SI NIST Chemistry WebBook 2-Naphthalenol]
{{cite EB1911 |wstitle=Napthols |volume=19 |pages=168–169 |short=1}}

Category:2-Naphthyl compounds