Sodium naphthalene

Sodium naphthalene is an organic salt with the chemical formula Na⁺[C₁₀H₈]⁻. In the research laboratory, it is used as a reductant in the synthesis of organic, organometallic, and inorganic chemistry. It is usually generated in situ. When isolated, it invariably crystallizes as a solvate with ligands bound to Na⁺.^[1]

Sodium naphthalene

Names
Preferred IUPAC name Sodium naphthalenide
Systematic IUPAC name Sodium naphthalen-1-ide
Other names sodium naphthalenide, sodium naphthalide
Identifiers
CAS Number	3481-12-7
3D model (JSmol)	Interactive image
ChemSpider	10004279 N
ECHA InfoCard	100.020.420
EC Number	222-460-3
PubChem CID	11829632
CompTox Dashboard (EPA)	DTXSID50188347
InChI InChI=1S/C10H8.Na/c1-2-6-10-8-4-3-7-9(10)5-1;/h1-8H;/q-1;+1 N Key: NCVIXNVCXNGGBW-UHFFFAOYSA-N N InChI=1/C10H8.Na/c1-2-6-10-8-4-3-7-9(10)5-1;/h1-8H;/q-1;+1 Key: NCVIXNVCXNGGBW-UHFFFAOYAJ
SMILES c1ccc2=C[CH][CH-]C=c2c1.[Na+]
Properties
Chemical formula	Na+[C10H8]−
Molar mass	151.164 g·mol−1
Appearance	Deep green crystals
Related compounds
Other anions	Lithium naphthalene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Preparation and properties

A solution of lithium naphthalenide, the lithium salt of naphthalene, in tetrahydrofuran.

The alkali metal naphthalene salts are prepared by stirring the metal with naphthalene in an ethereal solvent, usually as tetrahydrofuran or dimethoxyethane. The resulting salt is dark green.^[2][3][4] The anion is a radical, giving a strong EPR signal near g = 2.0. Its deep green color arises from absorptions centered at 463 and 735 nm.

Several solvates of sodium naphthalenide have been characterized by X-ray crystallography. The effects are subtle, the outer pair of CH−CH bonds contract by 3 pm and the other nine C−C bonds elongate by 2–3 pm. The net effect is that reduction weakens the bonding.^[5][6]

Reactions

Redox

With a reduction potential near −2.5 V vs NHE, the naphthalene radical anion is a strong reducing agent.^[1] It is capable of defluorinating PTFE and is commonly used for chemically etching PTFE to allow adhesion.^[7]

Protonation

The anion is strongly basic, and a typical degradation pathway involves reaction with water and related protic sources such as alcohols. These reactions afford dihydronaphthalene:

2 Na⁺[C₁₀H₈]⁻ + 2 H₂O → C₁₀H₁₀ + C₁₀H₈ + 2 NaOH

As a ligand

Alkali metal salts of the naphthalene radical anion are used to prepare complexes of naphthalene.^[8]

Related reagents

Main article: radical anion