Lithium naphthalene is an organic

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

with the chemical formula Li⁺. In the research laboratory, it is used as a

reductant In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are commonly reducing agents include the Earth meta ...

in the synthesis of organic, organometallic, and inorganic chemistry. It is usually generated in situ. Lithium naphthalene crystallizes with ligands bound to Li⁺.

Preparation and properties

The compound is prepared by stirring the metallic

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...

with naphthalene in an

ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...

eal solvent, usually as

tetrahydrofuran Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water- miscible organic liquid with low viscosity. It is ...

dimethoxyethane Dimethoxyethane, also known as glyme, monoglyme, dimethyl glycol, ethylene glycol dimethyl ether, dimethyl cellosolve, and DME, is a colorless, aprotic, and liquid ether that is used as a solvent, especially in batteries. Dimethoxyethane is mi ...

. The resulting salt is dark green. The reaction of naphthalene with lithium can be accelerated by sonication. Methods for assaying lithium naphthalene have been developed as well. The anion is a radical, giving a strong EPR signal near ''g'' = 2.0. Its deep green color arises from absorptions at 463, 735 nm. Several solvates of lithium naphthalene have been characterized by

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

. The effects are subtle, the outer pair of HC–CH bonds contract by 3 pm and the other nine C–C bonds elongate by 2–3 pm. Net: reduction weakens the bonding.

Reactions

Redox

With a

reduction potential Redox potential (also known as oxidation / reduction potential, ''ORP'', ''pe'', ''E_'', or E_) is a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and thereby be reduced or oxidised respe ...

near −2.5 V versus the normal hydrogen electrode, the naphthalene radical anion is a strong reducing agent.

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 LiC₁₀H₈ + 2H₂O → C₁₀H₁₀ + C₁₀H₈ + 2LiOH

As a ligand precursor

Alkali metal salts of the naphthalene radical anion are used to prepare complexes of naphthalene.

Related compounds

Many related

radical anion In organic chemistry, a radical anion is a free radical species that carries a negative charge. Radical anions are encountered in organic chemistry as reduced derivatives of polycyclic aromatic compounds, e.g. sodium naphthenide. An example of ...

s are known such as those derived from anthracene, with other alkali metals (especially sodium), and with diverse ligands attached to the alkali metal cations. Dilithium naphthalene is also known in the form i(tmeda)₂sub>2C₁₀H₈.

References

{{Lithium compounds Free radicals Lithium salts One-electron reducing agents Organolithium compounds Naphthalenes