Chlorobenzene is an aromatic compound with the chemical formula C₆H₅Cl, specifically an aromatic halide. At room temperature it is a colorless, flammable liquid, which is frequently used as a solvent and degreaser. In addition, it serves as raw material for the manufacture of numerous highly useful chemical compounds.

In the last century it served as the basis for the synthesis of the insecticide DDT, very useful in the eradication of diseases such as malaria. However, in 1970 its use was prohibited due to its high toxicity to humans. The chlorobenzene molecule is polar due to the higher electronegativity of chlorine relative to the carbon atom to which it is attached.

This results in chlorine having a moderate negative charge density δ- with respect to carbon and the rest of the aromatic ring. Likewise, chlorobenzene is practically insoluble in water, but it is soluble in liquids of an aromatic chemical nature, such as: chloroform, benzene, acetone, etc.

Additionally, Rhodococus phenolicus is a bacterial species capable of degrading chlorobenzene as the only carbon source.

Chemical Structure

The upper image illustrates the structure of chlorobenzene. The black carbon spheres make up the aromatic ring, while the white and green spheres the hydrogen and chlorine atoms, correspondingly.

https://chemistrypage.in/chlorobenzene-formula-chemistry-formula/

Unlike the benzene molecule, chlorobenzene has a dipole moment. This is because the Cl atom is more electronegative than the rest of the sp2-hybridized carbons.

For this reason there is not a uniform distribution of electron density in the ring, but rather the majority is directed towards the Cl atom.

According to this explanation, with an electron density map it could be corroborated that, although weak, there is a region δ- rich in electrons.

Consequently, the chlorobenzene molecules interact with each other through dipole-dipole type forces. However, they are not strong enough for this compound to exist in a solid phase at room temperature; for this reason it is a liquid (but with a boiling point higher than benzene).

Chlorobenzene Synthesis :

In industry, the method introduced in 1851 is used, in which chlorine gas (Cl2) is passed through liquid benzene at a temperature of 240 ºC in the presence of ferric chloride (FeCl3), which acts as a catalyst.

C6H6 => C6H5Cl

Chlorobenzene is also prepared from aniline in the Sandmayer reaction. Aniline forms benzenediazonium chloride in the presence of sodium nitrite; and benzenediazonium chloride forms benzene chloride in the presence of copper chloride.

Chlorobenzene Applications/Uses

Uses in organic synthesis

It is used as a solvent, defatting agent and serves as a raw material for the preparation of numerous highly useful compounds. Chlorobenzene was used in the synthesis of the insecticide DDT, currently in disuse due to its toxicity to humans.

Although to a lesser degree, chlorobenzene is used in the synthesis of phenol, a compound that has fungicidal, bactericidal, insecticidal, and antiseptic action and is also used in the production of agrochemicals, as well as in the manufacturing process of acetisalicylic acid.

It is involved in the manufacture of diisocyanate, a degreasing agent for automobile parts.

It is used to obtain p-nitrochlorobenzene and 2,4 dinitrochlorobenzene.

It is used in the synthesis of the compounds triphenylphosphine, thiophenol, and phenylsilane.

Triphenylphosphine is used in the synthesis of organic compounds; thiophenol is a pesticidal agent and pharmaceutical intermediate. Instead, phenylsilane is used in the silicone industry.

It is part of the raw material for the manufacture of diphenyl oxide, which is used as a heat transfer agent, in the control of plant diseases, and in the manufacture of other chemical products.

p-Nitrochlorobenzene obtained from chlorobenzene is a compound used as an intermediate in the manufacture of dyes, pigments, pharmaceuticals (paracetamol) and in rubber chemistry.

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Uses for synthesis of organic solvents

Chlorobenzene is also used as a raw material for the preparation of solvents used in the synthesis reactions of organic compounds, such as methylenediphenyldiisocyanate (MDI) and urethane.

MDI is involved in the synthesis of polyurethane, which has many functions in the manufacture of construction products, refrigerators and freezers, bedding, footwear, automobiles, coatings and adhesives, and other applications.

Likewise, urethane is a raw material for the production of adjuvant compounds for agriculture, paints, inks and cleaning solvents for use in electronics.

Chlorobenzene Medical uses

2,4 dinitrochlorobenzene has been used in dermatology in the treatment of alopecia areata. It has also been used in allergy studies and in the immunology of dermatitis, vitiligo and in the prognosis of the evolution in patients with malignant melanoma, genital warts and common warts.

It has had therapeutic use in patients with HIV. On the other hand, immunomodulatory functions have been attributed to it, an aspect that is subject to discussion.

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