Naphthalene

Naphthalene (also known as naphthalin, naphthaline, tar camphor, white tar, albocarbon, or naphthene) is a crystalline white solid hydrocarbon, with the empirical formula C₁₀H₈. It is volatile, forming a flammable vapor. Its molecules consist of two benzene rings joined at one side. It is manufactured from coal tar, and converted to phthalic anhydride for the manufacture of plastics, dyes and solvents. It is also used as an antiseptic and insecticide, especially in mothballs.

Structure and reactivity

A naphthalene molecule is composed of two fused benzene rings. (In organic chemistry, rings are fused if they share two or more atoms). Accordingly, naphthalene is classified as a benzenoid polycyclic aromatic hydrocarbon (PAH). Naphthalene has three resonance structures, which are shown in the above drawing. Naphthalene has two sets of equivalent hydrogens. The alpha positions are positions 1, 4, 5, and 8 on the above drawing. The beta positions are positions 2, 3, 6, and 7. The numbers 1-8 are used to

Like benzene, naphthalene can undergo electrophilic substitution. The major product generally has the electrophile in the "alpha" position. Sulfonation, however, gives a mixture of the "alpha" product 1-naphthalenesulfonic acid and the "beta" product 2-naphthalenesulfonic acid, with the ratio dependent on reaction conditions. Naphthalene can be hydrogenated to give tetralin, C₁₀H₁₈, also known as bicyclo[4.4.0]decane. Oxidation of naphthalene with chromate or permanganate, or catalytic oxidation with O₂ and a vanadium catalyst, gives phthalic acid.

Health effects

In humans, exposure to large amounts of naphthalene may damage or destroy red blood cells. This could cause the body to have too few red blood cells until it replaces the destroyed cells. Humans, particularly children, have developed this condition after ingesting mothballs or deodorant blocks containing naphthalene. Some of the symptoms of this condition are fatigue, lack of appetite, restlessness, and pale skin. Exposure to large amounts of naphthalene may also cause nausea, vomiting, diarrhea, blood in the urine, and a yellow color of the skin.

Animals sometimes develop cloudiness in their eyes after swallowing naphthalene. It is not clear if this also develops in humans.

When mice were repeatedly exposed to naphthalene vapors for two years, their noses and lungs became inflamed and irritated.

Name

The name naphthalene is derived from the Latin word of Iranian origin naphtha. Naphtha is a term for any volatile and usually flammable liquid hydrocarbon mixture, normally in the context of a solvent. It was earlier spelt naphthaline. The name phthalic acid is a shortened naphthalic acid, which is named from naphthalene.

description: white crystalline powder
molecular formula: C₁₀H₈
molecular weight: 128.6 g/mol
density: 4.42 g/cm^3 @20 C
boiling point: 218 C
melting point: 80.5 C