Lithium Naphthalene is the simplest condensed aromatic hydrocarbon composed of two benzene rings, commonly known as “sanitary ball”. Naphthalene occurs in industry in the form of crude naphthalene (industrial and pressed naphthalene) and refined naphthalene. The melting point is 80.28°C, the solid density is 1.145g/cm3, the liquid density (85°C) is 0.9752g/cm3, the specific heat capacity (100°C) is 1809J/(kg·K), and the refractive index (85°C) is 1.5898. Naphthalene is a colorless monoclinic crystal, volatile, sublimating, has a special odor, is flammable, and can form explosive mixtures with air; its petroleum ether solution is red-purple fluorescent under a mercury lamp, almost insoluble in water, soluble in ether, Alcohol, benzene and other solvents. Naphthalene vapor and dust can be poisoned when inhaled into the human body or absorbed through the skin, and the maximum allowable concentration in the air is 20mg/m3. Naphthalene is one of the basic raw materials for industries such as dyes, plastics, paints, medicines and pesticides. Naphthalene is more prone to substitution reactions than benzene—halogenation, nitration, sulfonation and Friedel-Crafts reactions. The electron density on the α-carbon atom is higher, and the rate of generating the α-substituted product is faster; the β-substituted product is more stable. The ratio of α- and β-substituted products in the substitution reaction depends on factors such as the nature of the reagents, catalysts, solvents, and temperature. For example, the halogenation and nitration reactions are irreversible, and generally produce mainly α-substituted products, in which the bromination reaction can occur without a catalyst.
The sulfonation reaction is reversible. When the temperature is low, the main product is α-naphthalene sulfonic acid. When the temperature is high, the main product is β-naphthalene sulfonic acid. When the temperature is increased, α-naphthalene sulfonic acid can be converted into more Stabilized beta-naphthalenesulfonic acid:

The sulfonation reaction is reversible. When the temperature is low, the main product is α-naphthalene sulfonic acid. When the temperature is high, the main product is β-naphthalene sulfonic acid. When the temperature is increased, α-naphthalene sulfonic acid can be converted into more Stabilized beta-naphthalenesulfonic acid:
