Naphthalene molecule can be viewed as the fusion of a pair of benzene rings. As such, naphthalene is classified as a benzenoid polycyclic aromatic hydrocarbon (PAH).

Polycyclic aromatic hydrocarbons (PAHs) are a class of chemicals that occur naturally in coal, crude oil, and gasoline. Naphthalene is a PAH that is produced commercially in the United States to make other chemicals and mothballs.

Mothballs are commonly made of naphthalene or para- dichlorobenzene, both of which are toxic to humans. These chemicals are solids at room temperature and are made into round balls, flakes or cakes that slowly change to a gas and become fumes in the air.

Mothballs in the U.S. contain very high concentrations of the chemical naphthalene or paradichlorobenzene as active ingredients. They are meant to be used in closed, airtight containers so that the fumes they produce are trapped. The trapped fumes build up and kill any clothes moths inside.

A polynuclear aromatic hydrocarbon is a hydrocarbon made up of fused aromatic ring molecules. These rings share one or more sides and contain delocalized electrons. Another way to consider PAHs is molecules made by fusing two or more benzene rings.

Naphthalene. Naphthalene is the simplest polycyclic aromatic hydrocarbon since it is only a bicyclic molecule made up of two aromatic benzenes. Naphthalene is also planar and has 4n + 2 pi electrons (10) giving it the stabilizing and resonating aromatic properties shared with benzene.

Updated November 25, 2019. A polynuclear aromatic hydrocarbon is a hydrocarbon made up of fused aromatic ring molecules. These rings share one or more sides and contain delocalized electrons. Another way to consider PAHs is molecules made by fusing two or more benzene rings.

The key difference between polycyclic and polynuclear aromatic hydrocarbons is that the term polycyclic aromatic hydrocarbon describes the presence of two or more cyclic structures fused to each other whereas the term polynuclear aromatic hydrocarbon describes the presence of more than one atom.

Naphthalene, with two fused rings, is the simplest polycyclic aromatic molecule. Note that all the carbon atoms except those at the points of fusion have a bond to a hydrogen atom. Naphthalene, which has 10 π electrons, satisfies the Hückel rule for aromaticity.

Naphthalene mothballs contain 99.9 percent naphthalene [3], and can range in weight from 0.5 g to 5 g [4].

Hydrocarbon molecule with two or more closed rings; examples are naphthalene, C10H8, with two benzene rings side by side, or diphenyl, (C6H5)2, with two bond-connected benzene rings. Also known as polycyclic hydrocarbon.

In the case of aniline, the molecule is aromatic. The benzene ring is, in agreement with Hückel’s rule, aromatic. The lone pair of electrons on the amino substituent clearly interact with the π system of the benzene ring as evidenced by the reduced basicity of aniline in comparison to ammonia.

Polynuclear aromatic hydrocarbons ( Chapter 1) are a class of compounds found throughout the environment in the air, in the soil, and in water. They are found naturally in crude oil, coal tar and coal, and are constituents of emissions produced during the incomplete combustion of hydrocarbons like coal, oil, gas, tobacco, and during forest fires.

Polycyclic Aromatic Hydrocarbons (PAHs) Factsheet. PAHs generated from these sources can bind to or form small particles in the air. High-temperature cooking will form PAHs in meat and in other foods. Naphthalene is a PAH that is produced commercially in the United States to make other chemicals and mothballs. Cigarette smoke contains many PAHs.

How PAHs Affect People’s Health. Workers who have been exposed to large amounts of naphthalene from skin contact with the liquid form and from breathing naphthalene vapor have developed blood and liver abnormalities. Several of the PAHs and some specific mixtures of PAHs are considered to be cancer-causing chemicals.

Other examples of PAH occurring in combustion processes include anthracene and phenanthrene (three rings), pyrene (four rings), etc. Most of the PAHs are known to have serious effects on health so attention has to be given to their formation even in trace amounts.