Naphthalene is a white, crystalline solid at room temperature (melting point, 176°F/80°C) with a strong coal-tar odor. Soluble in benzene, absolute alcohol, and ether, it is derived either from boiling coal-tar oils with subsequent crystallization and distillation, or from petroleum fractions following various catalytic processing operations. Naphthalene is toxic when inhaled. It is used as a moth repellent, insecticide, fungicide, lubricant, preservative, and antiseptic. Naphthalene has the chemical formula is C₁₀H₈. Structurally, the molecule consists of two benzene rings fused in such a way that they share two carbon atoms. (Figure 1)

Auguste Laurent (1807-1853, working with Jean-Baptiste Dumas (1800-1884) in France, succeeded in preparing pure naphthalene from coal tar and in studying its halogen derivatives in 1831. Out of Laurent's studies of naphthalene arose the modern notion that all compounds can be thought of as being derived from hydrocarbons by substitutions, with the number of carbon atoms the sole basis for classification into a series.