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Toluol from Wikipedia, the free encyclopedia

Structural formula and Kalottenmodell General information Name Toluol Other names Toluen, methyl benzene, Methylbenzen, phenylmethan Sum formula C7H8 CAS number 108-88-3 Short description colorless liquid Characteristics Mol mass 92,14 g/mol Density 0,87 g/cm3 Melting point -95 °C Boiling point 110,6 °C Steam pressure 29 hPa Safety references R and s-sentences R: 11-20 S: 16-25-29-33 MAK 50 ml/m3

So far possible and common, SI units were used. If not differently notes, the indicated data apply with standard conditions.


Toluol (also Toluen, methyl benzene, phenylmethan, after IUPACnomenclature Methylbenzen mentioned) is a colorless, blumig smelling, volatile liquid, which resembles the benzene in many characteristics. Toluol is an aromatic hydrocarbon, frequently replaces it as solvent the poisonous benzene. There is found among other things also in the gasoline. Table of contents [AnzeigenVerbergen] 1 historical information 2 characteristics 3 use 4 occurrences and emissions 5 production 6 reactions 7 dangers and metabolismus 8 literature 9 Web on the left of [work on]


Historical information

1844 were won toluol for the first time by dry distillation by Henri Etienne Sainte Claire Deville from tolubalsam; also its name is based on that. Of toluol then 1861 were made by the German chemist Joseph Wilbrand for the first time - only impure - TNT, 1880 could be made it then also in pure form of toluol. The large-scale production was taken up to Germany in the year 1891 over nitrating of toluol, this procedure is finally used still today. [work on]


Characteristics

Toluol is a simplest representative the alkylof benzene. At air it burns flame only incompletely with yellow, strong Russian that. The liquid smells blumig, stinging pleasantly (similarly as benzene) and has a smell threshold of 0,6 - 263 mg/m3. Toluol melts with -95 °C, simmers with 111 °C and is with standard conditions a colorless, clear, water-bright liquid, which is strongly refractive (refractive index: 1,4961). In water it is nearly insoluble (0.52 g/l); with kohlenstoffdisulfid, alcohol and ether it is mixable in each relationship. Also in chloroform, acetone and most further organic solvents toluol is well soluble. The dynamic viscosity amounts to 0.6 mPa s, toluol is thus more highly liquid than water. The heat value amounts to with 40.940 kJ/kg, its flash point lies with 4 °C and the ignition temperature with 535 °C. [work on]


Use

Toluol is substitute and substitute solution means for the similar, but poisonous benzene. As such it becomes frequent as solvent for resins, fats and oils, lacquers, sticking and coloring materials (nagellack) as well as many further materials used. It may be contained up to five percent by volume in the gasoline and this mixed, because it increases the octane number (anti-knock quality), in the USA will become up to 95 per cent of manufactured toluol fuels mixed. Toluol is basic material for the synthesis of the explosive 2,4,6-Trinitrotoluol, which admit better under the abbreviation TNT are, and many further chemicals, like for example of the preservative benzoic acid, of phenol, benzene, Caprolactam and Saccharin (in the rem EN pale mountain procedure). Furthermore it is used in the microscopy as lightening means. Occasionally it is used even despite its dangers as cleaning agent. Beside benzene and xylene it belongs to the so-called VTX aromatics, this is in the industry the three aromatic hydrocarbons with the greatest technical importance. [work on]


Occurrence and emissions

Toluol comes in the oil and in the light oil, which results with hard coal tar distillation, into smaller quantities forwards. Toluol is set free among other things from Kfz traffic, because there is found in the gasoline, and results in small quantities with the incomplete burn of organic materials. In the last years a decrease of the toluol missions is to be registered, the annual average amounts to for example in Rhineland-Palatinate 30 µg/m3, depending upon place can it however to larger fluctuations of this value come. Main mission factor is also around the 65 per cent Kfz traffic, 33 per cent is to the use of toluol products and 2 per cent to the toluol production to be due. The toluol missions are diminished in the terrestrial atmosphere, like with the benzene, after several days by hydroxyl radicals (OH radicals). [work on]


Production

In the industry it is won mainly from oil. During the Second World War it came into Germany because of the missing oil to bottlenecks during the toluol production, why it was made also of benzene and methanol. In addition it results with the production of Ethen and propen . The world production lies annually between 5.000.000 and 10.000.000 tons. Direct production from oil or by trockendestillation hard coal would not be economical however. Therefore it is won with the processing of oil by Cracken or Dehydrocyclisierung of n-heptane:

  • Dehydrocyclisierung of nheptane: Heptane is reformed to methyl cyclohexane and dehydrogenated afterwards to toluol.


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Reactions

Toluol is stably and relatively poorly reactive with standard conditions, with oxidizing agents and acids reacts it however violently. It is received similar reactions as phenol and benzene. Toluol attacks plastics and in glass containers is therefore kept. By oxidation (for example with sour potassium permanganatessolution) toluol over benzyle alcohol and Benzaldehyd can be converted to benzoic acid. The reaction behavior of toluol resembles that of the benzene. Toluol is received before all radical substitution reactions, elektrophile substitution reactions and radical addition reactions . Nukleophile substitution reactions are rarer.

In particular in the heat or under irradiation with light toluol with suitable reaction partners (for example bromine )can be received radical substitution reactions at group of methyls (see SSS rule).


Toluol reacts with bromine under heating up to Phenyltribrommethan and bromwasserstoff in form of a radical substitution.

Since toluol is relatively poorly reactive, elektrophile substitution reactions at it run off only relatively slowly. In presence of a suitable catalyst the reaction rate can be substantially increased (see KKK rule). Preferentially para and orthosubstituierte products develop.


Toluol reacts with nitric acid to Nitrotoluol and water. The actual nitrating Agenz (NO2+) is formed in presence of sulfuric acid from nitric acid. Over repeated nitrating TNT can be won.


Toluol reacts with bromine to pbromine toluol and bromwasserstoff. This reaction becomes intermediate byFeBr of 3 over itself screen end FeBr4- and Br+ catalyzes.

Technically important reactions


To toluol oxidizes and thereafter dehydrogenated, one develops for benzoic acid.


Driven and metabolismus

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Injurious to health (Xn).

Easily inflammatory (F).

Toluol works injurious to health (Xn) and is easy inflammatory (F). Toluol exhibits however not the poisonous effect of the benzene and does not work not hereditarygood-changing. This can be explained with another metabolismus. Toluol is hardly metabolisiert in contrast to the benzene by oxidation of the ring, but by main oxidation of the seitenkette to benzoic acid. The reason for it is the high selectivity of the Monoxygenasesystems P450 for the group of methyls of toluol. For this reason karzinogenes epoxy hardly develops as in the case of the benzene. The small quantities of epoxy can be diminished by conjugation atGlutathion, spontaneous intramolekulare relocation to the phenol or by enzymatic hydrolysis to the Diol.


Metabolismus of toluol

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In the form of benzoic acid and Hippursaeure toluol, apart from small quantities o-cresol, is separated over the urine.


Metabolismus of toluol into elimination products

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Toluol causes nerves -, for kidney and possibly also liver damage. Toluol is reproduction-endangering as well as fruit-damaging. The inhalation of toluol steams can lead to nonspecific symptoms such as tiredness, indisposition, feeling disturbances, disturbances of the movement co-ordination and the consciousness loss. With regular contact it can come to a toluol craze, which accompanies with amusements and excitation intoxications. Toluol steams have an anaesthetizing effect and to provoke the eyes and respiratory organs heavily, allergische reactions to toluol are possible. Toluol should be kept for on well ventilated places.

Toluol is even in small quantities, although it is not water soluble, water-endangering (WKG 2). It is biologically easily degradable. Starting from an air volume portion from 1,2 to 7 per cent it forms explosive mixtures.


Literature

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  • Evaluation of toluol and xylene immissions. E. Schmidt, Berlin (July 2000), ISBN 3503040714
  • Juergen Angerer:Prevention of vocationally conditioned health damage by benzene, toluol, Xylole and ethylbenzol. 1983, ISBN 3872473115
  • A Seeber, M Blaszkewicz, P Demes:Toluol in Tiefdruckereien : Final report to a research project. ISBN 3883836230
  • H. Dirt:Work unhealthy works. Reason toxicological-according to industrial medicine of mA K-values: Toluol. VCH, Weinheim (1985).


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Classification: Chemical compound

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