1-Nitroso-2-naphthol

1-Nitroso-2-naphthol is an organic compound with the formula C₁₀H₆(NO)OH. It is one of several possible nitrosonaphthols, and the most studied for applications as an indicator and a dye.^[2]

1-Nitroso-2-naphthol

Identifiers
CAS Number	131-91-9 Y
3D model (JSmol)	Interactive image
ChemSpider	8262
ECHA InfoCard	100.004.586
EC Number	205-043-0
PubChem CID	8580
UNII	757I55U2QX
CompTox Dashboard (EPA)	DTXSID9059622
InChI InChI=1S/C10H7NO2/c12-9-6-5-7-3-1-2-4-8(7)10(9)11-13/h1-6,12H Key: YXAOOTNFFAQIPZ-UHFFFAOYSA-N
SMILES C1=CC=C2C(=C1)C=CC(=C2N=O)O
Properties
Chemical formula	C10H7NO2
Molar mass	173.171 g·mol−1
Appearance	Yellowish-brown
Melting point	109.5 °C (229.1 °F; 382.6 K)
Hazards
GHS labelling:[1]
Pictograms
Signal word	Warning
Hazard statements	H302, H315, H319, H335, H400
Precautionary statements	P261, P264, P264+P265, P270, P271, P273, P280, P301+P317, P302+P352, P304+P340, P305+P351+P338, P319, P321, P330, P332+P317, P337+P317, P362+P364, P391, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis and reactions

1-Nitroso-2-naphthol can be prepared by treatment of 2-naphthol with nitrous acid:^[3]

C₁₀H₇OH + HNO₂ → C₁₀H₆(NO)OH + H₂O

Its conjugate base forms deeply colored complexes with iron(II) and cobalt(II), complexes [M(C₁₀H₆(NO)O)₃]^2-.^[4] The deep colors of these complexes results from the delocalized bonding within each five-membered chelate ring. These species can be classified as nitroso complexes.

See also

• Naphthol Green B, the iron complex of a sulfonated derivative of 1-nitroso-2-naphthol