Ethylbenzene

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Ethylbenzene
Skeletal formula Ball-and-stick model
Identifiers
Abbreviations EB
CAS number 100-41-4 YesY
PubChem 7500
ChemSpider 7219 YesY
UNII L5I45M5G0O YesY
DrugBank DB01722
KEGG C07111 YesY
ChEBI CHEBI:16101 YesY
ChEMBL CHEMBL371561 YesY
RTECS number DA0700000
Beilstein Reference 1901871
Jmol-3D images Image 1
Properties
Molecular formula C8H10
Molar mass 106.17 g mol−1
Appearance colorless liquid
Density 0.8665 g/mL
Melting point −95 °C (−139 °F; 178 K)
Boiling point 136 °C (277 °F; 409 K)
Solubility in water 0.015 g/100 mL (20 °C)
log P 3.27
Vapor pressure 9.998mmHg
Refractive index (nD) 1.495
Viscosity 0.669 cP at 20 °C
Dipole moment 0.58 D[1]
Thermochemistry
Specific
heat capacity
C
1.726 J/(gK)
Hazards
R-phrases R11 R20
S-phrases (S2) S16 S24/25 S29
Main hazards Flammable
NFPA 704
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasoline) Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 22.22 °C (72.00 °F; 295.37 K)
Explosive limits 1%-7.8%
LD50 5460 mg/kg
Related compounds
Related aromatic
hydrocarbons
styrene, toluene
Related compounds benzene
polystyrene
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Ethylbenzene is an organic compound with the formula C6H5CH2CH3. It is a highly flammable, colorless liquid with an odor similar to that of gasoline. This monocyclic aromatic hydrocarbon is important in the petrochemical industry as an intermediate in the production of styrene, the precursor to polystyrene, a common plastic material. In 2012, more than 99% of ethylbenzene produced was consumed in the production of styrene. Ethylbenzene is also used to make other chemicals, in fuel, and as a solvent in inks, rubber adhesives, varnishes, and paints. Ethylbenzene exposure can be determined by testing for the breakdown products in urine.

Physical and chemical properties[edit]

Ethylbenzene[2] is a colorless liquid that smells similar to gasoline with a sweet aroma, evaporates quickly and is highly flammable. It has a characteristic odor with an odor threshold at 2.3 ppm and a melting point of −95 °C (−139 °F) and a boiling point of 136 °C (277 °F).[3] It is classified as a monocyclic aromatic hydrocarbon since it is a compound that contains only carbon and hydrogen atoms.[2][4]

Occurrence and applications[edit]

Ethylbenzene occurs naturally in coal tar and petroleum, although this is not the main source of this compound.[5]

The dominant application of ethylbenzene is role as an intermediate in the production of polystyrene. Catalytic dehydrogenation of ethylbenzene gives hydrogen and styrene:

C
6
H
5
CH
2
CH
3
→ C6H5CH=CH2 + H
2

As of May 2012, greater than 99% of all the ethylbenzene produced is used for this purpose.

Niche uses[edit]

Ethylbenzene is added to gasoline as an anti-knock agent, meaning it reduces engine knocking and increase the octane rating. Ethylbenzene is often found in other manufactured products, including pesticides, cellulose acetate, synthetic rubber, paints, and inks.[5] Used in the recovery of natural gas, ethylbenzene many be injected into the ground.

Production[edit]

Ethylbenzene is produced in on a large scale by combining benzene (C
6
H
6
) and ethylene (C
2
H
4
) in an acid-catalyzed chemical reaction:

C
6
H
6
+ C
2
H
4
C
6
H
5
CH
2
CH
3

In 2012, more than 99% of ethylbenzene was produced in this way. Thus, manufacturers of ethylbenzene are the major buyers of benzene, claiming more than half of total output.[6]

Small amounts of ethylbenzene is recovered from the mix of xylenes by superfractioning, an extension of the distillation process.[2]

In the 1980s a zeolite-based process using vapor phase alkylation, offered a higher purity and yield. Then a liquid phase process was introduced using zeolite catalysts. This offers low benzene-to-ethylene ratios, reducing the size of the required equipment and lowering byproduct production.[7]

Approximately 24,700,000 tons were produced in 1999.[8]

Health effects[edit]

The acute toxicity of ethylbenzene is low, with an LD50 of about 4 grams per kilogram of body weight. The longer term toxicity and carcinogenicity is ambiguous.[8] Eye and throat sensitivity can occur when high level exposure to ethylbenzene in the air occurs. At higher level exposure, ethylbenzene can cause dizziness.[5] Once inside the body, ethylbenzene biodegrades to 1-phenylethanol, acetophenone, phenylglyoxylic acid, mandelic acid, benzoic acid and hippuric acid.[8]

As of September 2007, the United States Environmental Protection Agency (EPA) determined that drinking water with concentration of 30 parts per million (ppm) for one day or 3 ppm for ten days is not expected to have any adverse effect in children. Lifetime exposure of 0.7 ppm ethylbenzene is not expected to have any adverse effect either. The U.S. Occupational Safety and Health Administration (OSHA) limits exposure to workers to an average 100 ppm for an 8-hour work day, a 40-hour workweek.[5]

Ethylbenzene is classified as a possible carcinogen by the International Agency for Research on Cancer (IARC) however, the EPA has not determined ethylbenzene to be a carcinogen. The National Toxicology Program conducted an inhalation study in rats and mice. Exposure to ethylbenzene resulted in an increased incidence of kidney and testicular tumors in male rats, and trends of increased kidney tumors in female rats, lung tumors in male mice, and liver tumors in female mice.

As for all organic compounds, ethylbenzene vapors form an explosive mixture with air.[2] When transporting ethylbenzene, it is classified as a flammable liquid in class 3, Packing Group II.[2]

Environmental effects[edit]

Ethylbenzene is found mostly as a vapor in the air since it can easily move from water and soil.[5] A median concentration of 0.62 parts per billion (ppb) was found in urban air in 1999.[3] A study conducted in 2012 found that in country air the median concentration was found to be 0.01 ppb and indoors the median concentration was 1.0 ppb. It can also be released into the air through the burning of coal, gas, and oil. The use of ethylbenzene in industry contributes to ethylbenzene vapor in the air. After about three days in the air with the help of sunlight, other chemicals break down ethylbenzene into chemicals that can be found in smog.[5] Since it does not readily bind to soil it can also easily move into groundwater. In surface water, it breaks down when it reacts with chemicals naturally found in water.[9] Generally, ethylbenzene is not found in drinking water, however it can be found in residential drinking water wells if the wells are near waste sites, underground fuel storage tanks that are leaking, or landfills.[5]

As of 2012, according to the EU Dangerous Substances Directive, ethylbenzene is not classified as hazardous to the environment.[2]

Biodegredation[edit]

Certain strands of the fungus Cladophialophora can grow on ethylbenzene.[10]

References[edit]

  1. ^ Lange's Handbook of Chemistry (15th ed.). 1999. 
  2. ^ a b c d e f "ETHYLBENZENE : ENVIRONMENTAL, HEALTH & SAFETY GUIDELINES". CEFIC. Retrieved 14 February 2013. 
  3. ^ a b "Technology Transfer Network Air Toxics Web Site: Ethylbenzene". US Environmental Protection Agency. Retrieved 13 February 2013. 
  4. ^ --, William H. Brown ... [et al.]. (2009). Organic Chemistry. (5th ed. . ed.). Belmont, CA: Brooks/Cole Cengage Learning. pp. 56, 208. ISBN 9780495388579. 
  5. ^ a b c d e f g "Ethylbenzene". Agency for Toxic Substances and Disease Registry. Retrieved 12 February 2013. 
  6. ^ Market Study Benzene, published by Ceresana, July 2011 [1]
  7. ^ "Ethylbenzene (EB) Production and Manufacturing Process". PIERS. Retrieved 14 February 2013. 
  8. ^ a b c Vincent A.Welch, Kevin J. Fallon, Heinz-Peter Gelbke “Ethylbenzene” Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a10_035.pub2
  9. ^ "Ethylbenzene". eco-usa.net. Retrieved 12 February 2013. 
  10. ^ Francesc X. PRENAFETA-BOLDU; Andrea KUHN; Dion M. A. M. LUYKX; Heidrun ANKE; Johan W. van GROENESTIJN; Jan A. M. de BONT (April 2001). Isolation and characterisation of fungi growing on volatile aromatic hydrocarbons as their sole carbon and energy source 105 (4). pp. 477–484. 
  • National Toxicology Program. Toxicology and Carcinogenesis Studies of Ethylbenzene (CAS No. 100-41-4) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). TR No. 466. U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, Bethesda, MD. 1999.

External links[edit]