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Sodium naphthalenide, also known as sodium naphthalide, is an organic salt with the formula Na+C10H8−. In the research laboratory, it is used as a reductant in the synthesis of organic, organometallic, and inorganic chemistry. It has not been isolated as a solid, but it is usually prepared fresh before use.
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Preparation and properties
The alkali metal naphthalenides are prepared by stirring the metal with naphthalene in an ethereal solvent, usually as tetrahydrofuran or dimethoxyethane. The resulting salt is dark green. The anion is a radical, giving a strong EPR signal near g = 2.0, with a reduction potential near -2.5 V vs NHE. Its deep green color arises from absorptions centered at 463, 735 nm.
The anion is strongly basic, and a typical degradation pathway involves reaction with water and related protic sources. These reactions afford dihydronaphthalene:
2 NaC10H8 + 2 H2O → C10H10 + C10H8 + 2 NaOHRelated reagents
For some synthetic operations, sodium naphthalenide is excessively reducing (too negative), in which case milder reductants are selected. Larger rings give milder reductants. Sodium acenaphthalenide is milder by about 0.75 V.
The corresponding lithium salt, lithium naphthalenide, is also known.