1. 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.
2. 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.
5. Napthalene-Properties
• Molecular Formula • C10H8
• Molar Mass • 128.17 g/mol
• Appearance • White solid
• Density • 1.14 g/cc
• Melting Point • 80.26 oC
• Boiling Point • 218 oC
6. 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.
7. 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.
8. • Like benzene, naphthalene can undergo electrophilic aromatic
substitution.
