Toluene

Toluene
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Name	Toluene
Other names	Methylbenzene; phenylmethane
Formula	C7H8
Molar mass	92.14 g·mol−1
Appearance	Colorless liquid
Density	0.8669 g·cm−3 (20 °C)
Melting point	−95 °C
Boiling point	110.6 °C
Solubility	0.05 g·100 mL−1 (20 °C)
CAS number	108-88-3

Toluene

Introduction

Toluene is an aromatic hydrocarbon widely used as a solvent and chemical intermediate. It appears as a colorless, volatile liquid with a distinctive sweet, pungent odor and is produced and handled by numerous ExxonMobil, Shell plc, BP, Chevron Corporation, and TotalEnergies operations worldwide. Historically significant in the development of organic chemistry, toluene was characterized in studies associated with Friedrich August Kekulé, August Wilhelm von Hofmann, and later industrialized during the expansion of the Petroleum Industry and the rise of companies like Standard Oil and Royal Dutch Shell. Its trade and regulation intersect with agencies such as the United States Environmental Protection Agency, the European Chemicals Agency, and national ministries including the United Kingdom Department for Environment, Food and Rural Affairs and the Ministry of Ecology and Environment (China).

Physical and Chemical Properties

The molecule has the formula C7H8 and a methyl substituent on a benzene ring; its physical behavior has been examined in contexts involving Ludwig Boltzmann-related thermodynamics, Arrhenius activation concepts, and spectroscopic methods pioneered by Joseph von Fraunhofer and Max Planck. Toluene's refractive index, vapor pressure, and heat capacity have been measured in laboratories affiliated with institutions such as Massachusetts Institute of Technology, University of Cambridge, ETH Zurich, University of Tokyo, and California Institute of Technology. Its infrared and nuclear magnetic resonance spectra were characterized using equipment developed by companies like Bruker, Thermo Fisher Scientific, and Agilent Technologies. Chemically, toluene undergoes electrophilic aromatic substitution reactions studied in the context of mechanisms reported by Gilbert N. Lewis, Christopher Ingold, and Robert Robinson; it is also a substrate for oxidation and halogenation processes applied in research at Max Planck Institute for Coal Research and industrial labs at DuPont and BASF.

Production and Synthesis

Commercial production derives from catalytic reforming and toluene extraction units in refineries operated by firms such as ConocoPhillips, PetroChina, and Saudi Aramco; steam cracking and coal tar fractionation at facilities like Sasol and ArcelorMittal also yield toluene. Synthesis routes include methylation of benzene using methanol over zeolite catalysts developed in research at Shell Research and UOP LLC and Friedel–Crafts methylation catalyzed historically by agents associated with Charles Friedel and James Crafts. Laboratory-scale oxidations to benzoic acid employ reagents studied by Herbert C. Brown and protocols refined in academic groups at Harvard University and Stanford University. Separation and purification techniques such as extractive distillation and solvent extraction have been optimized with equipment from Emerson Electric and Siemens.

Industrial and Commercial Uses

Toluene serves as a solvent for paints, adhesives, and inks in manufacturing operations by Sherwin-Williams, 3M, H.B. Fuller, and Avery Dennison; it is an intermediate for production of benzene derivatives in facilities run by LyondellBasell and INEOS. It is a feedstock for synthesis of benzene via disproportionation processes used at plants by Chevron Phillips Chemical and for manufacture of polymers and resins employed by Dow Chemical Company and Eastman Chemical Company. Toluene was historically used as an octane booster in gasoline blending at refineries such as Shell Rotterdam Refinery and in racing fuels associated with motorsport organizations like Fédération Internationale de l'Automobile; it is also a precursor in synthesis of pharmaceuticals developed at companies including Pfizer, Roche, Novartis, and GlaxoSmithKline. Analytical laboratories in institutions such as Centers for Disease Control and Prevention and National Institutes of Health use toluene as a reference solvent in chromatographic methods standardized by International Organization for Standardization and the American Society for Testing and Materials.

Health and Safety

Occupational exposure has been addressed by regulatory bodies like the Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health following toxicology research linked to investigators at Johns Hopkins University, Mount Sinai Health System, and Karolinska Institutet. Acute inhalation affects the central nervous system; clinical manifestations and case reports have been published in journals affiliated with Mayo Clinic, Cleveland Clinic, and John Radcliffe Hospital. Chronic exposure concerns, including neurotoxicity and peripheral neuropathy, have been evaluated in cohort studies coordinated by the World Health Organization and the European Agency for Safety and Health at Work. Personal protective equipment guidance produced by International Labour Organization and emergency response protocols from National Fire Protection Association are widely used in industry.

Environmental Impact and Fate

Environmental monitoring networks managed by organizations such as United States Geological Survey, Environment Agency (England)', Environment and Climate Change Canada, and European Environment Agency track toluene concentrations in air, water, and soil. Atmospheric degradation proceeds via reaction with hydroxyl radicals in mechanisms studied by researchers at Scripps Institution of Oceanography and NCAR; photochemical smog formation links to studies by California Air Resources Board and New York State Department of Environmental Conservation. Biodegradation pathways have been characterized in microbial ecology labs at Wageningen University, University of Copenhagen, and National Taiwan University involving genera like Pseudomonas reported in publications from American Society for Microbiology. Contamination incidents at sites remediated under programs by the United States Department of Defense and United Nations Environment Programme illustrate legal and technical responses.

Regulation and Standards

Permissible exposure limits and environmental quality standards are enforced by agencies including OSHA, EPA, ECHA, and national ministries such as the Ministry of Health (Brazil), Ministry of Health and Family Welfare (India), and Japanese Ministry of Health, Labour and Welfare. Transport and classification follow criteria from the United Nations Economic Commission for Europe and the International Maritime Organization via the IMDG Code and the Globally Harmonized System of Classification and Labelling of Chemicals. Industry standards and testing methods are published by ASTM International, ISO, and consensus bodies like IEC and ANSI; product stewardship programs are managed by trade associations including the American Chemistry Council and the European Chemical Industry Council.

Category:Organic solvents