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Benzene
The chemical substance benzene has the molecular formula C6H6
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Benzene is categorized as a hydrocarbon because it only has carbon and hydrogen
atoms
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It belongs to the basic class of
petrochemicals
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The aroma of petrol is due to benzene which is a
colorless, extremely combustible chemical with a sweet smell
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Discovery:
The term "benzene" arises from "gum benzoin," an aromatic resin that has been used in
Southeast Asia since ancient times
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[16] By sublimating benzoin, an acidic substance known as "flowers of benzoin" or benzoic
acid was created
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[17] In 1825, Michael Faraday first discovered benzene from greasy residue
obtained from production of illuminating gas, naming it as; bicarburet of hydrogen
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He called it as benzin
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Charles Blachford Mansfield separated benzene from coal tar [22] in 1845 while working for
August Wilhelm von Hofmann
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Chemists gradually came to the conclusion that
benzene was a chemically linked compound to a variety of other compounds, forming a
chemical family
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[25] In 1997, benzene was detected in deep
space
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[47][48] The prefixes
ortho-, meta-, and para- were first used in 1869 by German chemist Carl Gräbe to designate the
precise relative locations of the substituents on a di-substituted aromatic ring (i
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,
naphthalene)
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[50]

Early Applications:
Ludwig Roselius made benzene's usage for decaffeinating coffee mainstream in 1903
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Later, this procedure was stopped
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Some of these benzene-containing
formulations were no longer produced after 1950, but Liquid Wrench was still produced until the
late 1970s and still included considerable levels of benzene
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It results from the incomplete combustion
of a variety of elements
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However, the synthesis of benzene
from petroleum became necessary in the 1950s due to the rise in benzene demand, particularly
from the expanding polymers industry
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On Mars, benzene [53][54][55] has
been found
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The lengths of the C-C bonds are longer than a double bond (135
pm), but they are less than a single bond (147 pm)
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Hexane, the parent alkane of benzene, has 14
hydrogen atoms, whereas benzene only has 6
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The molecule is planar
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This stability probably plays a role in the
distinctive molecular and chemical characteristics known as aromaticity
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Derivatives:
By replacing one or more of the hydrogen atoms in benzene's hydrogen atoms with another
functional group, numerous significant chemical compounds are created
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Biphenyl is created by fusing benzene rings C6H5-C6H5
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The limit of the fusion process is the hydrogen-free allotrope
of carbon, graphite
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Nitrogen is
present in the most significant variants
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Despite having a similar structural makeup, benzene cannot be
converted into pyridine
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[64]

Production:
Four chemical processes contribute to industrial scale production:
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Catalytic reforming
Toluene hydrodealkylation
Toluene disproportionation
Steam cracking

Catalytic Reforming:
In catalytic reforming, hydrogen gas is combined with a variety of hydrocarbons having boiling
temperatures between 60 and 200 °C
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In
these circumstances, rings are formed and hydrogen is lost, converting aliphatic hydrocarbons
to aromatic hydrocarbons
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The reformate aromatics extraction phase aims to create aromatics with the fewest
non-aromatic components possible
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Toluene Hydrodealkylation:
Toluene is converted into benzene through toluene hydrodealkylation
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Sometimes, in identical reaction conditions, higher temperatures are employed in place of a
catalyst
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Over 95% of reactions typically have a yield
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In contrast to standard BTX (benzene-toluene-xylene) extraction techniques, this way of
producing benzene is frequently referred to as "on-purpose" methodology
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Given that demand for para-xylene (p-xylene) far outweighs demand for other xylene isomers,
the TDP process may be improved upon using Selective TDP (STDP)
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Even the benzene-to-xylenes ratio
can be changed in some systems to favour xylenes
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Steam cracking can result in the production of pyrolysis petrol, a liquid by-product rich
in the benzene found in the feedstock used to make the olefins
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Other Methods:
There are numerous more ways to obtain benzene, notwithstanding their lack of commercial
importance
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Decarboxylation converts benzoic acid
and its salts into benzene
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Acetylene is converted to benzene through alkyne trimerization
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Uses:
Most compounds, including ethylbenzene (and other alkylbenzenes), cumene, cyclohexane,
and nitrobenzene, are made using benzene as an intermediary
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[65]
A precursor of styrene, which is used to create polymers and plastics like polystyrene, is created
from more than half of the world's benzene output
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Around 10% of the benzene produced worldwide is used to make cyclohexane, which is largely
utilized to create nylon fibers for use in textiles and engineering plastics
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China and the USA were the two
nations that consumed the most benzene in 2013, respectively
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Nowadays, benzene is frequently replaced by töluene in applications like fuel additives
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Benzene can also be made from toluene
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Reactions:
The most frequent reactions of benzene involve other groups replacing a proton
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Because it is
so nucleophilic, benzene can be substituted by alkyl carbocations and acylium ions to produce
substituted derivatives
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Benzene (or many other aromatic rings) are acylated with an acyl chloride in this reaction, which
uses a potent Lewis acid catalyst like aluminium chloride or iron(III) chloride as the catalyst
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The process of sulfonating benzene uses oleum, a combination of sulfuric acid and
sulphur trioxide
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In the process of
nitration, nitronium ions (NO2+), a potent electrophile created by mixing sulfuric and nitric acids,
react with benzene
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Chlorine is chlorinated to produce
chlorobenzene in the presence of an aluminium trichloride-based Lewis acid catalyst
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Heterogeneous catalysts are present while high hydrogen pressures are used to produce this
reaction
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Alkenes, however, can
also be hydrogenated at temperatures close to ambient
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They need temperatures higher than 100 °C
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Hydrogen cannot penetrate benzene in the absence of the catalyst
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However, benzene is selectively hydrogenated to the diene through the
non-catalytic process of birch reduction

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