Toluene

Toluene is a chemical compound that exists as a colorless liquid with scent of paint thinners as an aromatic hydrocarbon. In toluene, CH3, a univalent group, substitutes a hydrogen atom in benzene molecular shape. It is released from crude oil, volcanoes, water, or forest fires. Also, petroleum fuels and paint thinner emit toluene into the atmosphere. Toluene is widely used in various fields such as solvent, coating, paint, fuels, resin, and rubbers. It can harm people when they are exposed to excessive amount of toluene. It can cause dermatitis and damage on liver and kidney.

History
Toluene was named by Jöns Jakob Berzelius initially, and was derived from toluol that comes form the tropical Colombian tree Myroxylon balsamum.

Toxicity
Exposure to toluene may cause dermal symptoms and nervous system symptoms. However, severe and excessive exposure to it will affect one's kidney and liver. In animal experiments, mice and rats substantiate embryo toxicity and maternal toxicity of toluene that it can cause malformation of offspring, but malformation does not happen in rabbits. In humans, a few cases of spontaneous abortion and malformation after exposure to toluene have been observed. Also, hepatic or renal symptoms are barely observed. For example, no symptoms of hepatic damage had been seen among 153 workers who were exposed to 1 to 60 ppm of toluene.

Toluene toxicity is mainly observed in the central nervous system and in some cases, it also causes reproductive toxicity, aberrations of chromosomes, and breaks of DNA strands. Those effects have been proved through animal experiments with mice and rats and also in cultured mammalian cells.

Through experiments, scientists cannot find any association between cancer and the exposure to toluene. Some cohorts revealed elevated rates of lung cancer while the others have high rates of colorectal cancer or colon cancer. Also, they found that the sites of cancers are not related to the exposure of toluene. Also, according to animal carcinogenicity data, animals like mice and rats do not prove the relation between rates of cancer and toluene.

Properties
Toluene is more reactive than benzene when it reacts to electrophilic aromatic substitution. It goes through chlorination with FeCl3, sulfonation, and also nitration. However, if toluene is heated, it can result in dinitrotoluene and trinitrotoluene (TNT). Toluene goes through oxidation when it reacts with other reagents. With potassium permanganate, it results in benzoic acid.

Occurrences
Toluene can be naturally emitted from volcanoes, crude oil, and fires in forests, and also found in water and soil. In groundwater, surface water, and even in drinking water, scientists have found small amount of toluene. It is also found in the atmosphere since exhaustion of motor vehicle, thinners, solvent's containing toluene, and petroleum fuels release toluene.

Uses
Toluene is commonly used to mix the chemical substances. It is mainly composed of benzene, toluene diisocyanates, benzoic acid, benzyl chloride, benzoyl chloride, phenol, xylene, plasticizers, sodium benzoate, benzaldehyde, styrene, benzene derivatives, caprolactam, saccharine, pharmaceuticals, dyes, perfumes, TNT and detergents. Also, used in fuels, toluene is used in paints, rubber, resins, thinners in nitrocellulose lacquers and adhesives. However, although toluene has been used as a solvent, it becomes less used since solvent emissions are started to restricted by environmental and health regulations. In minor usage of toluene is in mattresses, automotive seats, coatings, polyurethane elastomers, or upholstery as toluene diisocyanate (TDI).

According to the National Occupational Exposure Survey, during 1981 to 1983 toluene has been exposed to about 2 million of workers in United States in various occupations. Since cleaning operations, laboratories, car repairing, painting, varnishing needs toluene to work, occupational exposure of toluene has been unavoidable.

With developments and technologies, toluene is ued to produce benzene and xylenes. To make benzene, reactions happen between toluene and hydrogen in the hydrodealkylation process. However, in the transalkylation process, C9 aromatics is needed with toluene to make xylenes.

According to United States- based consultant CMAI, more than half of toluene demand is consumed to make benzene and xylenes while about 25% of it is used in solvents, 15% in production of gasoline, and 7% in toluene diisocyanate (TDI). Also it estimated that more than 30% of toluene usage in West Europe is used to make benzene in hydrodealkylation plants, and about 25% to make gasoline. For the whole Europe, according to Dewitt & Co, 2.38 m tonnes of toluene were consumed in 2007 and 1.38 m tonnes were converted to xylenes and benzene. 526,000 tonnes were used in solvents. In North America, toluene is mainly used in gasoline and selective toluene disproportionation processes in 2006. Then hydrodealkylation processes, conventional toluene disproportionation, and toluene diisocyanate, and solvents follow the main usages. However, in Asia, toluene usage in solvents takes a lead about 40% of the whole demand. Next, toluene transaklyation to make xylenes is used the second most, and then toluene disproportionation, hydrodealkylation, toluene diisocyanate follow.

Preparation
CH3Cl + AlCl3 → CH3+ + AlCl4- C6H5H + CH3+ + AlCl4- → C6H5CH3 + HCl + AlCl3 C6H5Br + CH3Br + 2Na → C6H5CH3 + 2NaBr C6H4CH3OH (cresol) + Zn → C6H5CH3 (toluene) + ZnO CH3C6H4SO3H (toluenesulfonic acid) + HOH (steam) → C6H5CH3 (toluene) + H2SO4 (sulfuric acid) C6H6 + ClCOCH3 → C6H5COCH3 (acetophenone) + HCl C6H5COCH3 + 4H → C6H5CH2CH3 (ethyl benzene)
 * From benzene(Friedel–Crafts reaction)
 * From bromobenzene (Wurtz-Fittig reaction)
 * From cresol
 * From toluenesulfonic acid
 * From aromatic ketones

Biology
Toluene can act as a GABAA receptor positive allosteric modulator and non-competitive N-Methyl-D-aspartic acid (NMDA)receptor antagonist like 1,1,1-trichloroethane or alkylbenzenes. Also, through the forced swim test (FST) and the tail suspension test (TST), it proves to have antidepressant-like effects in rats.

Metabolism
Toluene's metabolism can explain its toxicity. Since it has low water solubility, toluene needs to be metabolized to exit the body. It is impossible to be excreted through sweat, urine, or feces. In metabolism, about 95% of toluene becomes benzyl alcohol after oxidization and the rest of 5% becomes benzaldehyde and cresols.

Potential Health effects
Too much exposure to toluene can cause confusion, headache, dizziness, drowsiness, and fatigue. It also cause skin sensations and numbness, even it can cause unconsciousness and death. Swallowing toluene would bring abdominal spasms and other symptoms similar to the that of inhalation. Chemical pneumonitis can occur as a result of aspiration of material into the lungs. Toluene causes irritation and skin can absorb it. Causes severe eye irritation with redness and pain. Chronic exposure of toluene decreases blood cell, bone marrow hypoplasia, and damage one's kidney and liver. Also, it results in drying, dermatitis, and redness. Toluene can aggravate the people with skin infection, or damaged kidney or liver. However, alchoholic drinks can increase the toxicity of toluene.
 * Inhalation
 * Ingestion
 * Skin Contact
 * Eye Contact
 * Chronic Exposure
 * Aggravation of Pre-existing Conditions

Possible Symptoms
◦Become tachypneic, or tachycardic
 * General

◦Hypotension

◦Fever

◦Smelling odor (Hair, breath, and clothing may smell of sweet solvent.)

◦Paint or oil stains may be seen on clothing.

◦Burning mouth, eyes, or throat

◦Nystagmus ◦Consciouslessness
 * Neurologic

◦Dizziness/ headaches

◦Confusion

◦Hallucinations

◦Amnesia

◦Paresthesias

◦Balance problems ◦Respiratory distress
 * Pulmonary

◦Dyspnea

◦Chest pain

◦Tachypnea

◦Cyanosis ◦Nausea
 * Gastrointestinal

◦Vomiting

◦Abdominal pain

◦Hematemesis

◦Jaundice

Production
 Worldwide Production of Toluene

Video
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Additional Information

 * ATSDR- Case Studies in Environmental Medicine: Toluene Toxicity U.S. Department of Health and Human Services (public domain)
 * Health Effects of Toluene Canadian Centre for Occupational Health and Safety
 * Toluene Prices and Pricing Information ICIS.com