Question

How many substances are found in coal tar?

Answer 1

Hint: Coal tar is a very thick liquid which is produced as a by-product of the production of coke and coal gas from coal. Coal tar comprises a lot of different chemicals. It contains around ten thousand chemicals. Most of the chemicals in coal tar are not even identified. Many commercially important compounds can be obtained from coal tar.

Complete answer:
Coal tar is produced by the thermal decomposition of coal. This process can also be called Pyrolysis. The composition of coal tar varies depending on the process and the type of coal used. The different types of coal are lignite, Bituminous and anthracite.
Components of coal tar include polycyclic aromatic hydrocarbons (4-rings: chrysene, fluoranthene, pyrene, naphthacene, benzanthracene, 5-rings: picene, benzo[a]pyrene, benzofluoranthene, perylene, 6-rings: benzopyrenes, di benzofluoranthene s, 7-rings: coronene). They also contain methylated and poly methylated derivatives, mono- and polyhydroxylated derivatives, and heterocyclic compounds. Sometimes coal tar can also contain benzene, toluene, xylenes and naphthalene. Most of the compounds described above are carcinogenic, meaning they can have the capacity to cause cancer in humans.
Tar acids and phenolic compounds are extracted from coal tar after it has been distilled. The bases such as pyridine extracted from coal tar have medicinal uses as solvent in many pharmaceutical products.

Note:
Derivatives of coal tar have analgesic properties. Paracetamol is a very common example for this category even though there are other pharmaceutical methods for its preparation today. There are a lot of medicines that were first prepared from coal tar distillation products.
Tar and bitumen are different substances even though the words are used interchangeably. Bitumen is used in tarring roads.