It is one of the most commonly used solvents in the organic chemical laboratory. Benzene melts at 5. 5° C (41. 9° F), boils at 80. 1° C (176. 2° F), and has a relative density of 0. 88 at 20° C (68° F). It is widely regarded as carcinogenic and, if inhaled in large quantities, is poisonous. The vapors are explosive, and the liquid violently flammable. Many compounds, such as nitrobenzene, are obtained from benzene. Benzene is also used in the manufacture of drugs and in the production of important derivatives, such as aniline and phenol (see Hogben, Lancelot.
Science for the Citizen: A Self-Educator Based on the Social Background of Scientific Discovery, 1999). Benzene and its derivatives are included in the important chemical group known as aromatic compounds. II. Discussion Benzene is only slightly soluble in water, but can be mixed in all proportions with acetone, alcohol, ether, or glacial acetic acid. It burns with a smoky flame. The vapor forms an explosive mixture with air, and has been used in parts of the world as a motor fuel.
At one time, most benzene was obtained from tars and gases produced during the making of coke for the iron and steel industry. Now, however, much of the world’s supply of benzene is obtained by the refining of petroleum. Moreover, the benzene molecule is believed to be shaped like a ring, rather than like a cube or a chain as are other hydrocarbon molecules. The theory of the benzene ring is an important principle in organic chemistry. The aromatic series of hydrocarbons are compounds containing benzene ring.
The theory of the structure of the benzene molecule was first stated by the German chemist August Kekuke in 1865. He suggested that the six carbon atoms of benzene were arranged in a hexagonal ring, with each of the six hydrogen atoms attached to one of the carbon atoms. Since each carbon atom has a valence of 4, alternate carbon atoms share two valence bonds in the benzene ring (see Aftalion, Fred and Benfey,Otto Theodor. A History of the International Chemical Industry, 2000).
Pure benzene burns with a smoky flame because of its high carbon content. When mixed with a large proportion of petrol it makes a satisfactory fuel. In Europe benzene mixed with some methylbenzene and other related compounds has long been added to motor fuels. The wisdom of this in the face of benzene's carcinogenic qualities has only recently been addressed as a concern. Benzene was discovered in 1825 by the English scientist Michael Faraday, and in 1842 it was made available in large quantities after it was found that coal tar contains benzene.
A ton of coal, if coked in a by-product oven, yields about 7. 6 liters (2 gallons) of benzene (see Audrieth, Ludwig Frederick. Salts, Acids, and Bases: Electrolytes Stereochemistry, 2001). Large quantities of benzene are now obtained from petroleum, either by direct extraction from certain types of crude oils or by chemical treatment of petroleum (hydroforming and cyclization). III. Conclusion The structure of the benzene molecule is of the utmost importance to the theory of organic chemistry.
The first to formulate the resonating ring structure described above was the German chemist Friedrich August Kekulé von Stradonitz, in 1865. For various reasons, 20th-century theorists found difficulties with this picture and instead developed a “molecular orbital” picture of electrons orbiting the entire molecule rather than particular carbon atoms. In the 1980s, however, more advanced studies returned to Kekulé's picture, but with the electrons in deformed orbits around their particular atoms.