The formula of toluene: what is toluene and how to get it?

The arenes to which toluene refers can be considered as derivatives of the ancestor and the first member of the homologous series - benzene. The general formula for compounds that belong to this class is C _n H _2n-6 . The molecules of aromatic hydrocarbons contain a benzene ring (a ring, a nucleus). The formula of toluene C ₇ H ₈ reflects the affiliation of the substance to this large group of organic compounds. To many people, toluene is known by another name - methylbenzene. The substance is widely used in industry, used as an organic solvent, stain remover and for other purposes.

What is toluene?

One of the most important arenas - toluene - is a methyl benzene derivative. Water-insoluble colorless liquid has a sweetish aroma, reminiscent of the smell of paints, varnishes, solvents.

The chemical formula of toluene - C ₇ H ₈ - can be written differently: C ₆ H ₅ -CH _3. In this case, the number of atoms remains the same, but the difference from benzene, which is in the methyl radical, is noticeable.

Using other principles of the nomenclature, the compound is called methylbenzene and phenylmethane. This is the same toluene, the general formula of which is C ₇ H _8. But in the first case, the emphasis is on the fact that one hydrogen atom of those connected with the carbon of the benzene ring is replaced by a methyl radical. For the second name, another approach has been chosen. It is believed that in methane, one hydrogen is replaced by a phenyl radical. This is a particle into which benzene is converted, giving off a hydrogen atom.

The structure of the molecule

The composition of an organic substance consisting only of carbon and hydrogen atoms reflects the formula of toluene. Ball-shaped and volumetric models give an idea of the structure of the molecule of the compound, its differences from substances of the same homologous series. There is a similarity between toluene and benzene, which consists in the presence of a ring of 6 carbon atoms in the state of sp ² -hybridization. Each of them forms three sigma-bonds with neighboring particles (two atoms of carbon and one hydrogen). Perpendicular to the ring there is a single electronic system of the remaining non-hybrid p-orbitals (one for six carbon atoms). As a result, the whole cycle, and hence the substance, toluene acquires considerable strength and stability. The structural formula of the compound includes the seventh carbon from the methyl group which is in the sp ^3- hybridization state. It is bonded to three hydrogen atoms, and the fourth link expends on a compound with one carbon in the benzene ring.

Structural formulas of methylbenzene

The electron density between the carbon atoms that form the aromatic core is distributed evenly. The phenomenon is reflected in the formula of benzene, toluene and other arenas by the sign of aromaticity (circle in the ring). The presence of a methyl radical at one of the carbon atoms in the nucleus is also noted. The connections between all particles are shown by dashes. The structural formula in this case reflects the composition and main features of the structure of the molecule of matter.

A simplified formula of toluene is a hexagon with a ring inside or dashes denoting a double bond. A methyl group can be present in any of the six nuclear atoms, they are equivalent to each other. The disadvantage of this method of image is obvious. The record does not give an idea of the composition of the substance and the equivalence of all carbon-carbon bonds in the ring.

Preparation of methylbenzene in the laboratory and industry

In the laboratory, toluene was first obtained in 1835-1938 by P. Peltier and A. Deville. The first scientist carried out distillation of pine gum, and the second used Toluansky balsam extracted from the South American tree of Toluifera in Colombia. So there was a trivial name for the substance - toluene. At present, a significant amount of methylbenzene gives distillation of oil and coal tar with subsequent purification. In the coking process, toluene is extracted from the coke oven gas. In the synthesis of styrene, it is released as a by-product of the reaction of benzene and ethylene. In the laboratory and industry, the production of toluene is carried out by various methods.

1. Dehydrocyclization of acyclic hydrocarbons. Toluene is prepared from heptane in the presence of a catalyst at a temperature of 300 ° C.
2. Alkylation of benzene, which was called the Friedel-Crafts reaction. Carried out in the presence of an AlCl3 catalyst or other catalysts: C ₆ H ₅ -H + CH ₃ Cl = C ₆ H ₅ -CH ₃ + HCl.
3. Reaction with bromobenzene: C ₆ H ₅ -Br + CH ₃ -Br + 2Na = C ₆ H ₅ -CH ₃ + 2NaBr.
4. Mixing of zinc and cresol: C ₆ H ₄ CH ₃ OH + Zn = C ₆ H ₅ CH ₃ + ZnO.
5. Treatment of toluenesulfonic acid.

Physical properties of methylbenzene

Toluene, the structural formula of which contains a benzene nucleus, exhibits physical properties typical of aromatic compounds.

1. A clear, colorless liquid emits a paint odor.
2. It hardens methylbenzene at low temperatures and begins to melt at -93 ° C.
3. The boiling point of toluene is 110.63 ° C. The density of the substance is 0.8669 g / ml.
4. The solubility of methylbenzene in water at a temperature of 20 ° C is 0.47 g / l. The molar mass of the substance M (C ₇ H ₈ ) = 92.14 g / mol.

Chemical properties of toluene: oxidation

The characteristics of all arenas are determined by a chemically stable cycle of six carbon atoms. The toluene formula is a benzene ring that is formally unsaturated and a methyl radical. Aromatic hydrocarbons are close in properties to alkenes, which are characterized by addition reactions. But hydrogen atoms in benzene molecules and its homologues can participate in substitution reactions, which brings arenas and alkanes closer together. Toluene is more reactive than benzene. The substance is characterized by oxidation reactions.

1. Combustion, which is accompanied by the release of carbon dioxide and the formation of water: C ₇ H ₈ + 9O ₂ = 7CO ₂ + 4H ₂ O.
2. In the reaction of toluene with potassium permanganate , the methyl group in the side chain of the molecule of the substance is oxidized to carboxyl. As a result of the reaction, benzoic acid is obtained.

Chemical reactions of the aromatic toluene nucleus

1. Bromination, which is carried out in the presence of catalysts. A halogenated compound is formed: C ₇ H ₈ + Br ₂ = C ₇ H ₇ Br + HBr.
2. Nitration of methylbenzene is carried out by a mixture consisting of concentrated nitric and sulfuric acids. The nitro group in toluene can occupy the ortho- and para position. The reaction proceeds by the mechanism of electrophilic substitution. At high temperature, explosive trinitrotoluene (TNT) is formed.
3. Hydrogenation with hydrogen on the catalyst leads to de-aromatization and the production of methylcyclohexane: C ₇ H ₈ + 3H ₂ = C ₇ H _14.
4. Chlorination under strong heating or under the influence of UV radiation is completed by the formation of hexachlorocyclohexane.

The use of methylbenzene

Toluene is widely used as a starting material in organic synthesis. It is an essential material in the production of many substances. Application of toluene:

• Obtaining dyes;
• Manufacturing of stain removers, detergents;
• Production of TNT explosives;
• Use as a solvent of adhesives, paints, synthetic perfumes and cleaning agents;
• Manufacture of paints for construction works;
• Release of products for nails;
• Production of pharmaceuticals;
• Increasing the octane number of fuel;
• Organic synthesis of benzoic acid, benzaldehyde, benzyl chloride, saccharin, benzyl alcohol and other substances;

Toluene acts as an industrial solvent in dry cleaners, it is used in the process of tanning leather. It is a precursor of a number of petroleum products, phenol, formaldehyde, pesticides and other compounds.

Toxicity Toxicity

Methylbenzene is a fire hazardous substance. The steam-air mixture explodes under certain conditions. It is easy to ignite liquid toluene. Structural formula gives an idea of the composition and structure, but does not contain information about the effect of the substance on the human body. It was found that toluene is toxic, has a carcinogenic effect. Pairs of methylbenzene freely penetrate through the skin, respiratory system, cause changes in the central nervous system, irritation of integumentary tissues, dermatitis. When inhaling the fumes of toluene, the person manifests inhibition, tremor, disrupted the activity of the vestibular apparatus. Work with toluene, paints, solvents in rubber gloves, carefully ventilate the room or use a hood. Methylbenzene is a weak narcotic substance, causing toluene toxicomania. Other forms of adverse effects of the substance:

• Eye irritation and color vision disorder;
• Prolonged exposure can lead to hearing loss;
• High concentration in the blood causes liver damage, kidney necrosis;
• Inhalation of a large number of vapors leads to dizziness, drowsiness, headache.

Conclusion

Toluene is produced in large quantities in petrochemical plants or obtained as a by-product in coke plants. The compound is a valuable raw material for large-scale organic synthesis, used in the pharmaceutical industry. Included is methylbenzene in many types of solvents, which are used in the work with paintwork materials. Toluene belongs to the classification of toxic compounds to the third hazard class. When working with a substance, the concentration of its vapor in the air should not exceed the values determined by sanitary and hygienic standards. Do not allow the appearance of open fire, sparks when handling toluene, this can lead to an explosion. There are also environmental problems associated with the release of toluene into the atmosphere:

• When burning oil, various types of fuel;
• In active volcanoes;
• In forest fires;
• When using solvents and paints.

Toxic properties of toluene, fire and explosion hazard require an acute handling of liquid substance and its vapors.