Benzene Created by: Tomáš Machula Filák Antonín
Benzene • Benzene, also known as C6H6, PhH, and benzol, is an organicchemical compound which is a colorless and flammable liquid with a pleasant, sweet smell. • Benzene is a known carcinogen. It is a component of gasoline. It is an important industrial solvent and precursor in the production of drugs, plastics, gasoline, synthetic rubber, and dyes. • Benzene is a natural constituent of crude oil, but it is usually synthesized from other compounds present in petroleum. • Benzene is an aromatic hydrocarbon, and the second [n]-annulene (-annulene). gasoline - benzín dyes – barviva rubber – guma crude - surový
General Systematic name Benzene Other names Benzol Molecular formula C6H6 Molar mass 78.11 g/mol Appearance Colorless liquid CAS number [71-43-2] Hazards R-phrases R45, R46, R11, R36/38,R48/23/24/25, R65 S-phrases S53, S45 Properties Density and phase 0.8786 g/cm³ Solubility in water 1.79 g/l (25 °C) Melting point 5.5 °C (278.6 K) Boiling point 80.1 °C (353.2 K) Viscosity 0.652 cP at 20 °C Structure Molecular shape Planar Dipole moment 0 D Properties of Benzene
History • Benzene was discovered in 1825 by the English scientist Michael Faraday, who isolated it from oil gas and gave it the name bicarburet of hydrogen. In 1833, the German chemist Eilhard Mitscherlich produced it via the distillation of benzoic acid (from gum benzoin) and lime. Mitscherlich gave the compound the name benzin. In 1845, the English chemist Charles Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar. Four years later, Mansfield began the first industrial-scale production of benzene, based on the coal-tar method. Michael Faraday
Production • Benzene may result whenever carbon-rich materials undergo incomplete combustion. It is produced naturally in volcanoes and forest fires, and is also a component of cigarette smoke. • Up until World War II, most benzene was produced as a byproduct of coke production in the steel industry. However, in the 1950s, increased demand for benzene, especially from the growing plastics industry, necessitated the production of benzene from petroleum. Today, most benzene comes from the petrochemical industry, with only a small fraction being produced from coal. • Three chemical processes contribute equally to industrial benzene production: catalytic reforming, toluene hydrodealkylation, and steam cracking. Byproduct – vedlejší produkt
Uses • In the 19th and early 20th centuries, benzene was used as an aftershave because of its pleasant smell. Prior to the 1920s, benzene was frequently used as an industrial solvent, especially for degreasing metal. As its toxicity became obvious, other solvents replaced benzene in applications that directly exposed the user to benzene. • As a gasoline additive, benzene increases the octane rating and reduces knocking. As a result, gasoline often contained several percent benzene before the 1950s, when tetraethyl lead replaced it as the most widely used antiknock additive. However, with the global phaseout of leaded gasoline, benzene has made a comeback as a gasoline additive in some nations. By far the largest use of benzene is as an intermediate to make other chemicals. The most widely produced derivatives of benzene are styrene, which is used to make polymers and plastics, phenol for resins and adhesives (via cumene), and cyclohexane, which is used in Nylon manufacture. Smaller amounts of benzene are used to make some types of rubbers, lubricants, dyes, detergents, drugs, explosives and pesticides.
Health Effects • Breathing very high levels of benzene can result in death, while high levels can cause drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion, and unconsciousness. Eating or drinking foods containing high levels of benzene can cause vomiting, irritation of the stomach, dizziness, sleepiness, convulsions, rapid heart rate, and death. • The major effect of benzene from chronic (long term) exposure is to the blood. Benzene damages the bone marrow and can cause a decrease in red blood cells leading to anemia. It can also cause excessive bleeding and depress the immune system, increasing the chance of infection. • The US Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 1 part of benzene per million parts of air (1 ppm) in the workplace during an 8-hour workday, 40-hour workweek. Exposure – vystaveni
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