**History and Discovery of Benzene:**
– Benzene derives from gum benzoin and has been known since ancient times.
– Benzene was first isolated by Michael Faraday in 1825.
– Eilhard Mitscherlich and Charles Blachford Mansfield made significant contributions to benzene’s discovery.
– The term ‘aromatic’ was first applied to benzene by Hofmann in 1855.
– Benzene was detected in deep space in 1997.
**Chemical Structure and Properties of Benzene:**
– Proposed benzene structures by Couper, Loschmidt, and Kekulé.
– Benzene has a boiling point of 80.1°C and specific solubility characteristics.
– It is classified as an aromatic hydrocarbon due to its cyclic pi bonds.
– Benzene’s stability and planar structure contribute to its aromatic properties.
– X-ray diffraction reveals the equal length of all carbon-carbon bonds in benzene.
**Applications and Uses of Benzene:**
– Ludwig Roselius popularized benzene for decaffeinating coffee.
– Benzene was used in various consumer products but its use has been limited due to toxicity.
– Benzene was a by-product of coke production before World War II.
– Post-war, benzene production shifted to petroleum due to increased demand.
– Today, most benzene is sourced from the petrochemical industry.
**Benzene Derivatives and Production Methods:**
– Important compounds like phenol, toluene, and aniline are derived from benzene.
– Biphenyl and fused aromatic hydrocarbons are formed by linking benzene rings.
– Production involves catalytic reforming, toluene hydrodealkylation, and toluene disproportionation.
– Toluene hydrodealkylation and steam cracking are processes used in benzene production.
– Catalytic reformates played a significant role in U.S. benzene production in the late 20th century.
**Toxicity and Health Concerns of Benzene:**
– Benzene is a known carcinogen and volatile organic compound.
– Its toxicity limits its use in consumer items.
– Benzene’s explosive limits and autoignition temperature are important safety considerations.
– Benzene’s presence in petroleum and coal raises health and environmental concerns.
– Understanding the health risks associated with benzene is crucial for its safe handling and use.
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon.
 Space-filling model
| |||
| |||
 Benzene at room temperature
| |||
| Names | |||
|---|---|---|---|
| Preferred IUPAC name
Benzene | |||
| Other names
Benzol (historic/German)
Phenane Phenylene hydride Cyclohexa-1,3,5-triene; 1,3,5-Cyclohexatriene (theoretical resonance isomers) [6]Annulene (not recommended) Phene (historic) | |||
| Identifiers | |||
3D model (JSmol)
|
|||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.000.685 | ||
| EC Number |
| ||
| KEGG | |||
PubChem CID
|
|||
| RTECS number |
| ||
| UNII | |||
CompTox Dashboard (EPA)
|
|||
| |||
| |||
| Properties | |||
| C6H6 | |||
| Molar mass | 78.114 g·mol−1 | ||
| Appearance | Colorless liquid | ||
| Odor | sweet aromatic | ||
| Density | 0.8765(20) g/cm3 | ||
| Melting point | 5.53 °C (41.95 °F; 278.68 K) | ||
| Boiling point | 80.1 °C (176.2 °F; 353.2 K) | ||
| 1.53 g/L (0 °C) 1.81 g/L (9 °C) 1.79 g/L (15 °C) 1.84 g/L (30 °C) 2.26 g/L (61 °C) 3.94 g/L (100 °C) 21.7 g/kg (200 °C, 6.5 MPa) 17.8 g/kg (200 °C, 40 MPa) | |||
| Solubility | Soluble in alcohol, CHCl3, CCl4, diethyl ether, acetone, acetic acid | ||
| Solubility in ethanediol | 5.83 g/100 g (20 °C) 6.61 g/100 g (40 °C) 7.61 g/100 g (60 °C) | ||
| Solubility in ethanol | 20 °C, solution in ethanol: 1.2 mL/L (20% v/v) | ||
| Solubility in acetone | 20 °C, solution in acetone: 7.69 mL/L (38.46% v/v) 49.4 mL/L (62.5% v/v) | ||
| Solubility in diethylene glycol | 52 g/100 g (20 °C) | ||
| log P | 2.13 | ||
| Vapor pressure | 12.7 kPa (25 °C) 24.4 kPa (40 °C) 181 kPa (100 °C) | ||
| Conjugate acid | Benzenium | ||
| Conjugate base | Benzenide | ||
| UV-vis (λmax) | 255 nm | ||
| −54.8·10−6 cm3/mol | |||
Refractive index (nD)
|
1.5011 (20 °C) 1.4948 (30 °C) | ||
| Viscosity | 0.7528 cP (10 °C) 0.6076 cP (25 °C) 0.4965 cP (40 °C) 0.3075 cP (80 °C) | ||
| Structure | |||
| Trigonal planar | |||
| 0 D | |||
| Thermochemistry | |||
Heat capacity (C)
|
134.8 J/mol·K | ||
Std molar
entropy (S⦵298) |
173.26 J/mol·K | ||
Std enthalpy of
formation (ΔfH⦵298) |
48.7 kJ/mol | ||
Std enthalpy of
combustion (ΔcH⦵298) |
-3267.6 kJ/mol | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards
|
potential occupational carcinogen, flammable | ||
| GHS labelling: | |||
     | |||
| Danger | |||
| H225, H302, H304, H305, H315, H319, H340, H350, H372, H410 | |||
| P201, P210, P301+P310, P305+P351+P338, P308+P313, P331 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | −11.63 °C (11.07 °F; 261.52 K) | ||
| 497.78 °C (928.00 °F; 770.93 K) | |||
| Explosive limits | 1.2–7.8% | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
|
930 mg/kg (rat, oral) | ||
LCLo (lowest published)
|
44,000 ppm (rabbit, 30 min) 44,923 ppm (dog) 52,308 ppm (cat) 20,000 ppm (human, 5 min) | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible)
|
TWA 1 ppm, ST 5 ppm | ||
REL (Recommended)
|
Ca TWA 0.1 ppm ST 1 ppm | ||
IDLH (Immediate danger)
|
500 ppm | ||
| Safety data sheet (SDS) | HMDB | ||
| Related compounds | |||
Related compounds
|
Toluene Borazine Divinylacetylene(isomer) Dewar benzene(isomer) | ||
| Supplementary data page | |||
| Benzene (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |||
.svg)
Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline. It is used primarily as a precursor to the manufacture of chemicals with more complex structures, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. Although benzene is a major industrial chemical, it finds limited use in consumer items because of its toxicity. Benzene is a volatile organic compound.
Benzene is classified as a carcinogen.[1]