Gas Library

naphthaleneNaphthalene (C10H8)

Naphthalene is an organic compound with formula C10H8. It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass.[1] As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings. It is best known as the main ingredient of traditional mothballs.

As a chemical intermediate, Naphthalene is used mainly as a precursor to other chemicals. The single largest use of naphthalene is the industrial production of phthalic anhydride, although more phthalic anhydride is made from o-xylene. Other naphthalene-derived chemicals include alkyl naphthalene sulfonate surfactants, and the insecticide 1-naphthyl-N-methylcarbamate (carbaryl). Naphthalenes substituted with combinations of strongly electron-donating functional groups, such as alcohols and amines, and strongly electron-withdrawing groups, especially sulfonic acids, are intermediates in the preparation of many synthetic dyes. The hydrogenated naphthalenes tetrahydronaphthalene (tetralin) and decahydronaphthalene (decalin) are used as low-volatility solvents. Naphthalene is also used in the synthesis of 2-naphthol, a precursor for various dyestuffs, pigments, rubber processing chemicals and other miscellaneous chemicals and pharmaceuticals.

Naphthalene sulfonic acids are used in the manufacture of naphthalene sulfonate polymer plasticizers (dispersants), which are used to produce concrete and plasterboard (wallboard or drywall). They are also used as dispersants in synthetic and natural rubbers, and as tanning agents (syntans) in leather industries, agricultural formulations (dispersants for pesticides), dyes and as a dispersant in lead–acid battery plates.
Naphthalene sulfonate polymers are produced by reacting naphthalene with sulfuric acid and then polymerizing with formaldehyde, followed by neutralization with sodium hydroxide or calcium hydroxide. These products are commercially sold in solution (water) or dry powder form.

•    Sulfonation Step (sulfuric acid plus naphthalene):
H2SO4 + C10H8 → C10H7-SO3H + H2O
•    Polymerization Step (naphthalenesulfonic acid plus formaldehyde):
C10H7-SO3H + CH2-O → C10H7-SO3H-(C10H7-SO3H)n + H2SO4
•    Neutralization Step (naphthalene sulfonic acid condensate plus sodium hydroxide):
C10H7-SO3H-(C10H7-SO3H)n + NaOH → C10H7-SO3Na-(C10H7-SO3Na)n + H2O + Na2SO4