Toluene

The toluene , also called methylbenzene or phénylméthane is a transparent, insoluble liquid in the Eau and having an odor characteristic pointing out that of the solvent for painting. This odor points out that somewhat, douceâtre, of the related Benzène. It is a aromatic Hydrocarbure very widespread used like industrial starting product or Solvant.

History

The name of toluene drift of the older name toluöl which refers to the extract of tolu, an aromatic extract of the tropical tree Myroxylon balsamum from which it was extracted for the first time. One owes this name to the Swedish chemist Jöns Jacob Berzelius. Its synthesis was discovered by Rudolf Fittig.

Chemical properties

The toluene reacts like a aromatic Hydrocarbure normal by aromatic Substitution électrophile. The group Méthyle makes it 25 times more reactive roughly than the Benzène in this kind of reactions. By sulphonation it gives the paratoluenesulfonic Acide, while its chlorination by the Chlore in the presence of ferric chloride gives a mixture of isomers ortho and chlorotoluene para. Nitration by the nitric acid gives a mixture of ortho- and para-nitrotoluene. While heating, the reaction continues to give the Dinitrotoluène and finally the Trinitrotoluène (TNT) which is explosive.

The group Méthyle can also react in other reactions of Oxydation. The Permanganate of potassium gives the Benzoic acid , while the chromyle chloride gives the Benzaldéhyde. A Halogénation in ridicalizing conditions gives benzyl halides. For example, with the N-bromosuccinimide in the presence of AIBN, one obtains the Bromure of benzyl.

The catalytic Hydrogénation of toluene gives the méthylcyclohexane. Because of the particular stability of the aromatic system, this reaction requires a high pressure of Hydrogène.

Preparation

Toluene is present in small proportion in the Crude oil. It is usually produced by catalytic Reformage in the manufactoring process of the gasoline. One also obtains it by Craquage in the manufactoring process of the ethylene or then, starting from coal. Its final purification is done by Distillation or Extraction.

Uses

Toluene is used to raise the Number octane in the Carburant S. It is also used as Solvant for the Peinture S. One makes use of it like product of departure for various industrial processes: the synthesis of the rubber, the phenol, TNT, the toluene diisocyanate necessary to obtain the foam of Polyurethane. One also makes use of it in the Imprimerie, the Adhésif S, the Laque S, and the Tannage of the Cuir.

Precautions & Metabolism

The toluene vapor inhalation is harmful and induced nauseas with higher amounts. The chronic toluene inhalation in a prolonged way causes irreversible damage with the brain.

The Toxicité of toluene is explained by its Métabolisme. As toluene is very slightly water soluble, it cannot leave the organization by the traditional ways (urine, deposit, perspiration). It must initially be metabolized to be excreted. The methyl group of toluene oxidizes more easily than the aromatic nucleus. This reaction is carried out by the Cytochrome S P450. It follows that 95% of toluene are transformed into benzylic Alcool. In fact the 5% remaining create the toxic metabolites, the epoxy S of the aromatic nucleus. The great majority of these epoxies is combined with the Glutathione, however the little which manages to escape seriously damages the cellular machinery while going alkyler some Protéine S, and even DNA.

Toluene is excreted mainly in the form of Benzoic acid - obtained by enzymatic oxidation of benzylic alcohol - and in the form of Hippuric acid obtained by conjugation of the benzoic acid with the Glycine.

Sentences of risk and the Councils of prudence

Rules Labelling

  • R11 : Easily flammable

  • R38: Irritating for the skin
  • R48/20: Harmful: risk serious effects for health in the event of exposure prolonged by inhalation.
  • R63: Possible risk during the pregnancy of harmful effects for the child
  • R65: Harmful: can cause an attack of the lungs in the event of ingestion.
  • R67: The vapor inhalation can cause somnolence and giddinesses.

  • S2 : To preserve out of the range of the children

  • S36/37: To wear suitable protective clothing and an apparatus of protection of the yeux/du face.
  • S46: In the event of ingestion to consult a doctor immediately and to show him packing or the label.
  • S62: In the event of ingestion not to make vomit: to consult a doctor immediately and to show him packing or the label

External bonds

  • toxicological Card of the INRS

  • international Card of safety

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