INTRODUCTION TO METHYLBENZENE

Methylbenzene or(tōl`yo͞oēn’) toluene

(mĕth’əlbĕn`zēn), C7H8, colorless liquid aromatic hydrocarbon that melts at −95°C; and boils at 110.8°C;. It is insoluble in water but highly soluble in most organic solvents. Toluene is obtained from coal tar and petroleum by distillation. It is used as a solvent and as a starting material for the synthesis of many compounds, including dyes and explosives. When toluene is treated with a mixture of nitric and sulfuric acids (a process known as nitration), trinitrotoluene
or TNT
, CH3C6H2(NO2)3, crystalline, aromatic compound that melts at 81°C;. It is prepared by the nitration of toluene.
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 (TNT) is produced.

 

Toluene

(or methylbenzene), a colorless, flammable liquid with an odor similar to that of benzene. Melting point, –95°C; boiling point, 110.6°C; density, 0.8669 g/cm3 at 20°C.

Toluene forms explosive mixtures with air in proportions of 1.27–7.0 percent by volume. Its ignition temperature is 552°C, and its flash point is 4.4°C. Toluene is miscible with most organic solvents; at 22°C, 0.492 g of toluene dissolves in 1 kg of water, and 0.526 g of water dissolves in 1 kg of toluene.

Methylbenzene is a component of certain petroleums. In industry, it is isolated mainly from coal tars and the products of the thermal conversion of petroleum fractions. Toluene is an important chemical raw material. It is characterized by reactions of electro-philic substitution in the aromatic ring and transformations of the methyl group, with retention of the ring. Electrophilic substitution occurs more readily than in benzene and is directed mainly at the para (4-) and ortho (2,6-) positions.

Thus, the nitration of toluene using a mixture of nitric and sulfuric acids yields, in sequence, the mononitro and dinitro derivatives and then 2,4,6-trinitrotoluene (TNT). Transformations of the methyl group occur through a radical mechanism. For example, chlorination under ultraviolet irradiation and with heating leads to benzyl chloride, C6H5CH2C1, benzal chloride, C6H5CHC12, and trichloromethylbenzene, C6H5CC13. Nitration with a solution of HNO3 in acetic acid yields α-nitrotoluene, C6H5CH2NO2, and oxidation yields benzyl alcohol, C6H5CH2OH, benzaldehyde, C6H5CHO, and benzoic acid, C6H5COOH.

Methylbenzene is used in the manufacture of dyes, explosives, pharmaceuticals, and various intermediates. It is also used as a solvent in the production of plastics, paints, varnishes, and printing inks, as well as in the rubber industry.

Methylbenzene is less toxic than benzene. The maximum permissible concentration of toluene vapor in the air is 0.05 mg per liter.

Methylbenzene

C6H5CH3 A colorless, aromatic liquid derived from coal tar or from the catalytic reforming of petroleum naphthas; insoluble in water, soluble in alcohol and ether, boils at 111°C; used as a chemical intermediate, for explosives, and in high-octane gasolines. Also known as methylbenzene; phenylmethane; toluol.

INTRODUCTION TO METHYLBENZENE

ASSIGNMENT : INTRODUCTION TO METHYLBENZENE ASSIGNMENT MARKS : 10  DURATION : 1 week, 3 days

 

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