Years later, specifically in 1834, the German chemist Eilhardt Mitscherlich produced benzene by heating benzoic acid. In 1845, it was the turn of German chemist AW Von Hofmann who isolated benzene from coal tar.
- 1 History
- 2 Features
- 3 Properties
- 4 Importance
- 5 dangers
History Of benzene :
Since then, the structure of benzene has been studied. Thus, the German chemists Joseph Loschmidt (in 1861) and August Kekulé Von Stradonitz (in 1866) suggested a structural formula with six carbon atoms with alternative single and double covalent bonds, which was then modified by Kekulé, where the double bonds made oscillations between the atoms of the aromatic ring, forming two equivalent structures.
In 1931, the American chemist Linus Pauling proposed that benzene had a unique structure, which was a resonance hybrid of both Kekulé structures.
According to the experiments, the single (CC) and double (C = C) covalent bonds have a bond length of 0.154 nm and 0.134 nm, respectively. However, all carbon bonds in benzene are equal to 0.139 nm.
The International Union of Pure and Applied Chemistry (IUPAC) recommends the use of one of the resonance forms to represent the benzene molecule, avoiding its representation by its resonance hybrid (hexagon with a circle in the center).
features of benzene
- Molar mass: 78.11 g / mol
- Density: 0.8765 (20) g / cm 3
- Boiling Point: 80.1 ° C
- Melting Point: 5.5 ° C
- Dipole moment: 0 D (debye)
- Water solubility: 0.8 g / L (15 ° C)
Properties of benzene :
Benzene is a colorless or light yellow liquid at room temperature, with a sweet and highly flammable odor , evaporates quickly in the air, is soluble in ethanol and chloroform , and is slightly soluble in water (0.18%).
Today, crude oil is the main source of benzene. However, it can be found in volcano gas emissions and forest fires.
Importance of benzene :
Benzene is a very important compound because various substances are manufactured from it for industrial use , using hydrogenation, sulfonation, nitration, Friedel-Crafts acylation, Friedel-Crafts alkylation, chlorination and bromination techniques.
Its main activity is as a solvent in the pharmaceutical and chemical industry, and as an intermediary in the synthesis of chemical products.
The most synthesized chemical is ethylbenzene, which, from dehydrogenation, forms styrene, and then polystyrene.
The second main use is in the production of phenol. Benzene can also be a raw material in the production of aniline, rubbers, lubricants, dyes, detergents, medications and pesticides.
In addition to being a precursor to the substances that will later be used in the production of plastics, resins, nylon and synthetic fibers.
Dangers Of benzene :
Benzene is highly toxic, carcinogenic and mutagenic and is absorbed through contact with mucous membranes, skin, inhalation and ingestion.
It acts directly on the Central Nervous System (CNS), causing effects such as headaches, vomiting, dizziness, among others. In addition, its continuous exposure causes anemia, leukemia and metabolic acidosis.
It is important to invest in individual protection measures during manufacturing processes, as well as in a strict inspection of products that may be contaminated with benzene and their replacement in processes by less toxic molecules.
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