Toluol

toluol (also Toluen, methyl benzene, Phenylmethan, after IUPAC - nomenclature 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. Itis contained among other things also in the gasoline.

Structural formula and Kalottenmodell
Strukturformel des Toluol Kalottenmodell des Toluol
general
name toluol
other names
  • Toluen
  • methyl benzene
  • Methylbenzen
  • Phenylmethan
sum formula C 7 H 8
CAS number 108-88-3
short description colorless liquid
characteristics
mol mass 92.14 g/mol
density 0.87 g/cm ³
melting point -95 °C
boiling point 110.6 °C
steam pressure 29 hPa
Flash point of 4 °C
safety references
of Gefahrensymbole
Xn
F
lightinflammatory
R
and S-sentences

R and S-sentences for toluol were changed injurious to health:

  • R: 11-38-48/20-63-65-67
  • S: 36/37 46 62

source: Official journal OF the European union L 152/1 of 30. April 2004

MAK 50 ml/m ³ (190 mg/m ³)
ASKED 1,70mg/l in the blood after laminating ones
as far as possible and common, are used SI-UNITs. If not differently notes, the indicated data apply with standard conditions.

Table of contents

historical information

1844 toluol was won for the first time by Henri Etienne Sainte Claire Deville by dry distillation from Tolubalsam; also its name is based on that. From toluol 1861 of the German chemist Joseph Wilbrand became for the first time - only impure - TNTmanufactured, 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 this very day.

characteristics

toluol is the simplest representative that alkylbenzene. 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/m ³. Toluol melts with -95 °C, simmers with 111 °C and is 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 solventstoluol 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 40,940 kJ/kg, its flash point lies with 4 °C and the ignition temperature with 535 °C.


occurrence and emissions

toluol come in the oil andin the light oil, which results with hard coal tar distillation, in 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, like for example when smoking. Into the latterYears is to be registered a decrease of the toluol missions, the annual average amounts to for example in Rhineland-Palatinate 30 µg/m ³, 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 on the use ofTo attribute toluol products and 2 per cent to the toluol production. The toluol missions are diminished in the terrestrial atmosphere, like with the benzene, after several days by hydroxyl radicals (OH-radicals).

production

in the industry is won it mainly from oil. During the Second World War it came into Germanybecause 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 throughTrockendestillation of hard coal would not be economical however. Therefore it is won with the processing of oil by Cracken or Dehydrocyclisierung of n-heptane:

  • <math> \ mathrm {C_7H_ {16} \ rightarrow C_7H_ {14} + H_2 \ rightarrow C_7H_8 + 4 \, H_2} </math>
  • Dehydrocyclisierung of n heptane: Heptane is reformed to methyl cyclohexane and thereafterto toluol dehydrogenates.

Toluol occurs also in cigarettes.

Photochemically it is accessible by isomerization of Cycloheptatrien.

reactions

toluol it is stably and relatively poorly reactive however violently with standard conditions, with oxidizing agents and acids reacts. It is received similar reactions as phenol andBenzene; the reactivity of toluol lies between these two connections. Toluol attacks plastics and in glass containers is therefore kept. By oxidation (for example with sour potassium permanganates - solution) toluol over benzyle alcohol and Benzaldehyd can be converted to benzoic acid. Toluol goes above 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 andBromwasserstoff 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 bromineto p bromine toluol and Bromwasserstoff. This reaction becomes intermediate by FeBr of 3 over itself screen end FeBr 4 - and Br + catalyzes.
Toluol reacts with nitric acid to Nitrotoluol and water. The actual nitrating agent (NO 2 +) becomes in presence from sulfuric acid Nitric acid in an educated manner. Over repeated nitrating TNT ( trinitrotoluene) can be won.

Technically important reactions

  • < math> \ mathrm {C_7H_8 + O \ rightarrow C_7H_8O - H_2O + O \ rightarrow C_6H_5CHO + O \ rightarrow C_7H_7O_2}< /math>
To toluol oxidizes and thereafter dehydrogenated, one develops for benzoic acid.

dangers and Metabolismus

toluolworks injurious to health (Xn) and is easy inflammatory (F). Toluol works not hereditarygood-changing, is however frequently contaminated with benzene. The smaller Giftigkeit of toluol opposite benzene can be explained with another Metabolismus. Toluol hardly becomes contrary to the benzene by oxidation of the ring, butmainly by oxidation of the Seitenkette to benzoic acid metabolisiert. The reason for it is the high selectivity of the Monoxygenasesystems P 450 for the group of methyls of toluol. For this reason karzinogenes epoxy hardly develops as in case of the benzene. The small quantities of epoxy can by conjugation on Glutathion, spontaneous intramolekulare relocation to the phenol or by enzymatic hydrolysis to the Diol to be diminished.

Metabolismus of toluol.

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

Metabolismus of toluol into elimination products.

Toluol causes nerve, kidney andpossibly 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 anaesthetizingAnd the eyes and respiratory organs provoke effect 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. Between an air volume portion of1,2 to 7 per cent it forms explosive mixtures.

literature

  • sub-committee effect questions a LAYMAN: Evaluation of toluol and xylene immissions. Erich Schmidt publishing house, Berlin 1997, ISBN 3503040714
  • Jürgen Angerer: Prevention of vocationally conditioned health damage by benzene, toluol, Xylole and Ethylbenzol. 1983, ISBN 3872473115
  • A Seeber, M Blaszkewicz, P Demes:Toluol in low printering: Final report to a research project. ISBN 3883836230
  • H. Dirt: Work unhealthy works. Reason toxicological-according to industrial medicine of MAK values: Toluol. VCH, Weinheim (1985).

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