Benzene is the simplest organic compound and an aromatic hydrocarbon. It is the parent compound of the various important aromatic compounds. It is colorless liquid and has a characteristic odor, and primarily it is used in the production of the polystyrene. Benzene is a carcinogen as it is highly toxic, and the exposure to the benzene may cause Leukemia. Even the exposure to the small amounts may cause neurological disorders, aplastic anemia by affecting the bone marrow, damage to the immune system and excessive bleeding. So, strict control is implemented on benzene emissions. The majority of the non-industrial applications of the benzene are also limited due to the same reason.
Benzene is a colorless, clear, highly volatile, liquid and flammable compound that belongs to the category of the aromatic hydrocarbons and has an odor like that of gasoline. Benzene is obtained as a byproduct of the oil refining processes and is found in the crude oils. Benzene was discovered in 1825 by Michael Faraday who was an English Scientist. In 1834 EilhardtMitscherlich who was a German Scientist heated the benzoic acid with the lime and produced benzene. In 1845 benzene was isolated from the coal tar by the German chemist A.W. Von Hoffman.
Since its discovery, the structure of benzene is of much interest. By using the modern bonding models, the structure and stability of the benzene are explained in the terms of delocalization of the six electrons. Here, in this case, the delocalization is referring to the attraction of the electron by the six carbons present in the ring instead of only one or two of them. Due to this delocalization, the electrons are more strongly held thus making the benzene less reactive and more stable, as compared to that of unsaturated hydrocarbon. Resultantly the hydrogenation of the benzene occurs more slowly than the hydrogenation of the alkenes. The oxidation of benzene is much more difficult than the oxidation of the alkenes.
Experimental studies by using the X-ray diffraction reveals that the benzene has a planar structure and the distance between each carbon to carbon bond is 1.40 angstroms. The boiling point of the benzene is 80.1 degrees Celsius and it’s melting point is 5.5 degrees Celsius. Benzene is freely soluble in the organic solvents but slightly soluble in the water. The density of benzene is less than the water so it easily floats on the water surface and its vapors are heavier than the air.
There was a time when benzene was entirely obtained from the coal tar but since the 1950s the methods of obtaining the benzene from the coal tar have been replaced by the petroleum processes. Each year more than half of the produced benzene is converted to the ethylbenzene then to the styrene and later to the polystyrene. Benzene is used to prepare the aniline which is used in dyes and for the preparation of the dodecylbenzene which is an important ingredient of the detergents. Benzene is being used in the industry as a chemical intermediate, as a solvent and for the synthesis of various chemicals.
