Naphthalene-1-sulfonic acid is an organic compound with the formula C₁₀H₇SO₃H. A colorless, water-soluble solid, it is often available as the dihydrate C₁₀H₇SO₃H^.2H₂O. It is one of two monosulfonic acids of naphthalene, the other being the more stable naphthalene-2-sulfonic acid. The compound is mainly used in the production of dyes.^[1]

Naphthalene-1-sulfonic acid

Names
Preferred IUPAC name Naphthalene-1-sulfonic acid
Other names 1-naphthalenesulfonic acid
Identifiers
CAS Number	85-47-2
3D model (JSmol)	Interactive image
Beilstein Reference	2099069
ChEBI	CHEBI:30895
ChEMBL	ChEMBL1160029
ChemSpider	6553
ECHA InfoCard	100.001.464
EC Number	246-676-2
Gmelin Reference	366290
KEGG	C16201
PubChem CID	6812
UNII	0SJH61WM2J
CompTox Dashboard (EPA)	DTXSID7048033
InChI InChI=1S/C10H8O3S/c11-14(12,13)10-7-3-5-8-4-1-2-6-9(8)10/h1-7H,(H,11,12,13) Key: PSZYNBSKGUBXEH-UHFFFAOYSA-N
SMILES C1=CC=C2C(=C1)C=CC=C2S(=O)(=O)O
Properties
Chemical formula	C10H8O3S
Molar mass	208.23 g·mol−1
Appearance	white solid
Melting point	139–140 °C (282–284 °F; 412–413 K)
Solubility in water	good
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H314, H351, H411
Precautionary statements	P201, P202, P260, P264, P270, P273, P280, P281, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P321, P330, P363, P391, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Naphthalene-1-sulfonic acid undergoes many reactions, some of which are or were of commercial interest. Upon heating with dilute aqueous acid, it reverts to naphthalene. Fusion with sodium hydroxide followed by acidification gives 1-naphthol. Further sulfonation gives 1,5-naphthalene-disulfonic acid. Reduction with triphenylphosphine gives 1-naphthalenethiol.