Thursday, December 23, 2021

Discovery of benzene

Michael Faraday, an English scientist isolated a pure compound from the oily mixture in the year of 1825. Faraday succeeded in isolating the compound by distillation and crystallization of the light mobile oil left behind in the gas cylinders.

He named this liquid “bicarburet of hydrogen” and found that the boiling point to be 80 °C. He determined elemental analysis evidenced hydrogen-to-carbon ratio of 1:1, corresponding to an empirical formula of CH.

In 1834, Eilhardt Mitscherlich a German chemist conducted vapor density measurements on benzene. He synthesized the same compound by heating benzoic acid, isolated from gum benzoin, in the presence of lime.

Like Faraday, Mitscherlich found that the empirical formula was CH. A vapor-density measurement showed the molecular weight of about 78, for a molecular formula of C6H6. He named it as benzin, since it was derived from gum benzoin and now it is called, benzene.

German chemist August Wilhelm von Hofmann in 1845 successfully isolated benzene from coal tar. German chemists Joseph Loschmidt (in 1861) and August Kekulé von Stradonitz (in 1866) independently proposed a cyclic arrangement of six carbons with alternating single and double bonds.

In 1861, Loschmidt started writing a sort of ring structure for benzene with a circle symbolizing the six carbons to which were sticking six smaller circles representing the six hydrogen atoms.

August Kekulé, used the principles of structural theory to postulate a structure for the benzene molecule. He suggested that the carbon atoms of benzene are in a ring. They are bonded to each other by alternating single and double bonds, and one hydrogen atom is attached to each carbon atom.
Discovery of benzene

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