Chemistry Reference
In-Depth Information
BENZENE (C
6
H
6
)
Properties
Clear, colorless, flammable liquid that boils at 80°C
(176°F) and freezes at 5.5°C (42°F). It has a very
characteristic odor. Recently it has been found to
be toxic and is suspected of being a human
carcinogen. Exposure to it should be very limited
or, preferably, avoided.
Commercial grades
Available in three grades: refined-535, refined-485
(nitration grade), and industrial. The numbers
following the grade refer to the freezing point
specification times 100. It is shipped in steel drums,
tank trucks, and tank cars under heavily regulated
conditions.
Uses
It is used as a chemical raw material for a myriad of
everyday products such as plastics, detergents,
textile fibers, drugs, dyes, and insecticides. It is also
found in gasoline with other aromatic hydrocarbons.
Manufacture
Benzene used to be made from coal, but it is now
made from petroleum by two different routes:
catalytic reforming of naptha and hydrodealkylation
of toluene. The first route provides toluene as a by-
product for the second route.
Producers
ExxonMobil, Chevron Phillips, Equistar, Koch, Dow,
Citgo, BP Chemicals, and many others.
Benzene was first isolated in 1825 by Michael Faraday in London, but its
structure remained somewhat of a mystery for over a century. In 1865, in
what is now thought of as one of the most important pronouncements in the
science of chemistry, a German chemist by the name of August Kekule
suggested that there are alternating double bonds in the benzene ring and
that they continuously trade places with each other. In the 1930s, the late
chemist Linus Pauling offered convincing evidence in favor of Kekule's
theory using a mathematical treatment known as quantum mechanics.
