Polynuclear aromatic compound• Polycyclic aromatic hydrocarbons (PAHs), also

known as poly-aromatic hydrocarbons or polynuclear aromatic hydrocarbons are potent atmospheric pollutants that consist of fused aromatic rings and do not contain heteroatoms or carry substituents.

• Napthalene is the simplest example of a PAH. • PAHs occur in oil, coal, and tar deposits, and are

produced as byproducts of fuel burning. • As a pollutant, they are of concern because some

compounds have been identified as carcinogenic, mutagenic, and teratogenic.

Polynuclear aromatic compound• The simplest PAHs, are phenanthrene and

anthracene, which both contain three fused aromatic rings.

• PAHs may contain four-, five-, six- or seven-member rings, but those with five or six are most common.

• Naphthalene, consisting of two coplanar six-membered rings sharing an edge, is another aromatic hydrocarbon. By formal convention, it is not a true PAH, though is referred to as a bicyclic aromatic hydrocarbon.

Polynuclear aromatic compoundsCompound

Anthracene Benzopyrene

Chrysene Coronene

Corrannulene Tetracene

Naphthalene Pentacene

Phenenthrene Pyrene

Triphenylene Ovalene

Napthalene• Naphthalin

Napthalene-Properties• Molecular Formula

• Molar Mass

• Appearance

• Density

• Melting Point

• Boiling Point

• C10H8

• 128.17 g/mol

• White solid

• 1.14 g/cc

• 80.26 oC

• 218 oC

Napthalene Properties• Naphthalene, also known as naphthalin, bicyclo[4.4.0]deca-

1,3,5,7,9-pentene or antimite is a crystalline, aromatic, white, solid hydrocarbon with formula C10H8 and the structure of two fused benzene rings.

• It is volatile, forming a flammable vapor, and readily sublimes at room temperature, producing a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass.

Structure and Reactivity• A naphthalene molecule is derived by the fusion of a pair of

benzene rings. • Unlike benzene, the carbon-carbon bonds in naphthalene are not of

the same length.• Like benzene, naphthalene can undergo electrophilic aromatic

substitution. • For many electrophilic aromatic substitution reactions, naphthalene

reacts under milder conditions than does benzene. • For example, whereas both benzene and naphthalene react with

chlorine in the presence of a ferric chloride or aluminium chloride catalyst, naphthalene and chlorine can react to form 1-chloronaphthalene even without a catalyst.

• Similarly, whereas both benzene and naphthalene can be alkylated using Friedel-Crafts reactions,

• naphthalene can also be alkylated by reaction with alkenes or alcohols, with sulfuric or phosphoric acid as the catalyst.

• Like benzene, naphthalene can undergo electrophilic aromatic substitution.