Some questions about benzene

Haven’t heard of it; please advise from downstairs.

Benzene (C6H6) is a colorless, sweet-tasting transparent liquid at room temperature, with a strong aromatic odor. Benzene is flammable, toxic, and also a carcinogen. Benzene is a hydrocarbon and also the simplest aromatic compound. It is insoluble in water, soluble in organic solvents, and can also be used as an organic solvent itself. Benzene is a basic raw material in the petrochemical industry. The production volume of benzene and the technological level of its production are **one of the indicators of the development level of the petrochemical industry**. The ring system in benzene is called the benzene ring, and it is the simplest aromatic ring. The structure of benzene with one hydrogen atom removed is called phenyl, denoted by Ph. Therefore, benzene can also be represented as PhH. Table of Contents: Chinese meaning, History, Structure, Valence bond theory, Molecular orbital model, Physical properties, Chemical properties, Substitution reactions, Addition reactions, Oxidation reactions, Others, Photoisomerization, Production methods, Extraction from coal tar, Extraction from petroleum, Separation of aromatic hydrocarbons, Toluene dealkylation, Toluene disproportionation and alkylation transfer, Other methods, Detection methods, Industrial uses, Health hazards, Toxicological data, Exposure limits, Metabolism, Symptoms of poisoning, Clinical manifestations of acute benzene poisoning, First aid measures. Chinese meaning, History, Structure, Valence bond theory, Molecular orbital model, Physical properties, Chemical properties, Substitution reactions, Addition reactions, Oxidation reactions, Others, Photoisomerization, Production methods, Extraction from coal tar, Extraction from petroleum, Separation of aromatic hydrocarbons, Toluene dealkylation, Toluene disproportionation and alkylation transfer, Other methods, Detection methods, Industrial uses, Health hazards, Toxicological data, Exposure limits, Metabolism, Symptoms of poisoning, Clinical manifestations of acute benzene poisoning, First aid measures. Staudte (filled) model of benzene. Chinese meaning: ① In the Tang dynasty pronunciation system: bu cun qie, pronounced as “běn”. 　　②According to the \"Yu Pian\": Benchui refers to grass that grows in clusters. 　　③\"Book of Jin: Biography of Wei Heng\": Crops and plants bear ears of grain. Detailed character annotations. 　　④Benzene (C6H6) is an organic compound and the simplest aromatic hydrocarbon in terms of structure. At room temperature, it is a colorless, sweet-smelling transparent liquid with a strong aromatic odor. Benzene is flammable and toxic, and it is classified as a Group 1 carcinogen by IARC. Benzene is insoluble in water but soluble in organic solvents, and it can also be used as an organic solvent itself. Benzene is a basic raw material in the petrochemical industry. The production volume of benzene and the technological level of its production are **one of the indicators of the development level of the petrochemical industry**. The ring system in benzene is called the benzene ring, and it is the simplest aromatic ring. The structure of benzene after one hydrogen atom has been removed is called phenyl; phenyl is denoted by Ph. Therefore, benzene can also be represented as PhH. 　　CAS number: 71-43-2 　　RTECS number: CY1400000 　　SMILES: C1=CC=CC=C1 　　Chemical formula: C6H6 　　Molar mass: 78.11 g mol-1 　　Density: 0.8786 g/mL 　　Melting point: 278.65 K (5.5 ℃) 　　Boiling point: 353.25 K (80.1 ℃) 　　Solubility in water: 0.18 g/100 ml of water 　　Standard molar entropy at 298 K: 173.26 J/mol·K 　　Standard molar heat capacity at 298.15 K: 135.69 J/mol·K 　　Flash point: -10.11℃ (closed cup) 　　Autoignition temperature: 562.22℃. 　　Structure: Planar hexagon. History: Benzene was first synthesized in the early 18th century during research on using gas as a lighting source. 　　Between 1803 and 1819, G. T. Accum produced many products, some of which were found to contain trace amounts of benzene when analyzed using modern methods. 　　In 1825, Michael Faraday isolated benzene of higher purity from the thermal decomposition products of substances such as fish oil, calling it “bicarburet of hydrogen”. Furthermore, some physical properties of benzene and its chemical composition were determined, and the carbon-to-hydrogen ratio of the benzene molecule was explained. 　　In 1833, Milscherlich determined the empirical formula of the benzene molecule, which is C6H6, consisting of 6 carbon atoms and 6 hydrogen atoms. 　　In 1845, the German chemist Hoffmann discovered benzene in the light fractions of coal tar, and his student C. Mansfield subsequently processed it for purification. Later, he invented a crystallization method to refine benzene. He also conducted research on industrial applications, pioneering methods for the processing and utilization of benzene. 　　In 1861, chemist Johann Jasef Loschmidt first proposed a structure for benzene in which single and double bonds alternated, but his work was not given much attention. 　　Kekulé’s bond-bending model: In 1865, Friedrich Kekulé, in his paper \"Researches on Aromatic Compounds,\" reconfirmed the structure of benzene as proposed four years earlier; this structure of benzene was thus named the \"Kekulé structure.\" He explained this structure by saying that the positions of the double bonds in the ring are not fixed and can move rapidly, which results in 6 carbon atoms being equivalent. Through his studies of monochlorinated and dichlorinated derivatives of benzene, he discovered that benzene has a ring structure with each carbon atom bonded to one hydrogen atom. 　　Furthermore, James Dewar discovered an analog of benzene ； Named “Duwa benzene,” it has been proven to be obtainable from benzene under light exposure. 　　In 1865, benzene became an industrial product. It was initially recovered from coal tar. As its uses expanded, production continued to rise, and by 1930 it had become one of the world’s top ten products by tonnage. Structure The delocalized large π-bonds in the benzene molecule give benzene its special aromaticity due to its benzene ring structure. The benzene ring is the simplest aromatic ring, consisting of a six-membered ring formed by six carbon atoms, with a group attached to each carbon atom; in benzene, all six of these groups are hydrogen atoms. 　　Research has shown that the carbon atoms in the benzene ring’s main chain are not connected by the single and double bonds as previously believed (as proposed by Kekulé); rather, the bond between every pair of carbon atoms is identical, being a bond that is neither a double bond nor a single bond. (It can be understood as an averaged bond, lying between a single bond and a double bond, possessing the properties of both; it can undergo substitution as well as addition.) Bond theory Ring olefins with a carbon count of 4n+2 (where n is a positive integer; benzene corresponds to n=1) and a structure in which single and double bonds alternate are called annulenes; benzene is one such annulene. The benzene molecule is a planar molecule, with all 12 atoms lying in the same plane; the 6 carbon atoms and 6 hydrogen atoms are arranged evenly. The length of the C-H bond is 1.08 Å, while the length of the C-C bond is 1.40 Å, values that lie between those of single and double bonds. All bond angles in the molecule are 120°, and the carbon atoms are all sp2 hybridized. Each carbon atom also has a remaining p orbital perpendicular to the molecular plane, with one electron in each orbital. Six orbitals overlap to form a delocalized large π bond. According to Linus Pauling’s resonance hybridization theory, the presence of resonance hybrids in benzene is the reason for the high stability of the benzene ring, and it is also what gives the benzene ring its aromatic properties. 　　 Molecular orbital model: From the perspective of molecular orbital theory, the σ bonds in the benzene ring can be considered as resulting from the interaction of the 6 p orbitals of benzene, which forms 6 π molecular orbitals. Among these, ψ1, ψ2, and ψ3 are bonding orbitals with lower energy, while ψ4, ψ5, and ψ6 are antibonding orbitals with higher energy. ψ2, ψ3 and ψ4, ψ5 are two pairs of degenerate orbitals. In its ground state, the electron cloud distribution of benzene is the result of the superposition of three bonding orbitals; therefore, the electron cloud is evenly distributed above and below the benzene ring as well as on the ring atoms, forming a closed electron cloud. It is the source of the circulating current generated by benzene molecules in a magnetic field. Physical properties: Benzene has a boiling point of 80.1°C and a melting point of 5.5°C. At room temperature, it is a colorless, aromatic, transparent liquid that is highly volatile. Benzene has a lower density than water, at 0.88 g/ml, but its molecular weight is greater than that of water. Benzene is insoluble in water; at most 1.7 g of benzene can dissolve in 1 liter of water ； However, benzene is a good organic solvent with a strong ability to dissolve organic molecules as well as some non-polar inorganic molecules. 　　Benzene can form an azeotrope with water, with a boiling point of 69.25°C and a benzene content of 91.2%. Therefore, benzene distillation is often added in reactions that produce water in order to remove it. 　　The saturated vapor pressure within the range of 10–1500 mmHg can be calculated using Antoine’s equation: lgP = A – P/(C + t). The parameters are A = 6.91210, B = 1214.645, and C = 221.205. Here, P is in mmHg and t is in °C. Chemical properties There are roughly three types of chemical reactions involving benzene molecules: one is a substitution reaction that occurs between other groups and the hydrogen atoms on the benzene ring ； One is an addition reaction that occurs at the C=C double bond ； One is the breakage of the benzene ring. 　　 Substitution reaction 　　Main entries: Substitution reaction, Electrophilic aromatic substitution 　　Under certain conditions, the hydrogen atoms on the benzene ring can be replaced by halogens, nitro groups, sulfonic acid groups, hydrocarbon groups, etc., to form corresponding derivatives. Due to different substituents as well as varying positions and numbers of hydrogen atoms, a different number of isomers with various structures can be formed. 　　The electron cloud density of the benzene ring is high, so the substitution reactions that occur on it are mostly electrophilic substitution reactions. Electrophilic substitution reactions are representative reactions of aromatic rings. In the electrophilic substitution of benzene, the position of the second substituent depends on the type of the original substituent. 　　Halogenation reaction The general formula for the halogenation of benzene can be written as: PhH + X2 → PhX + HX During this reaction, the halogen molecule dissociates under the action of both benzene and a catalyst; X+ attacks the benzene ring, while X- combines with the catalyst. 　　Taking bromine as an example, when liquid bromine is mixed with benzene, bromine dissolves in benzene to form a reddish-brown liquid; no reaction occurs. However, upon adding iron filings, the bromine reacts with benzene under the catalysis of the resulting ferric tribromide. The mixture begins to simmer, and the reaction releases heat while producing reddish-brown bromine vapor. The condensed gas forms white mist when it comes into contact with air (HBr). Catalytic mechanism: 　　FeBr3 + Br- → FeBr4- 　　PhH + Br + FeBr4- → PhBr + FeBr3 + HBr 　　The mixture after the reaction is poured into cold water, where a reddish-brown oily mass (containing bromine) settles at the bottom of the water. After washing with dilute alkaline solution, colorless liquid bromobenzene is obtained. 　　In industry, the substitutes of chlorine and bromine in halobenzenes are the most important. 　　Nitration reaction: Benzene and nitric acid can produce *** in the presence of concentrated sulfuric acid as a catalyst. PhH+HO-NO2——→PhNO2+H2O. The nitration reaction is a highly exothermic reaction; it is easy to form monosubstituted products, but further reactions proceed more slowly. 　　Sulfonation reaction: Benzene can be sulfonated to form benzenesulfonic acid using concentrated sulfuric acid or fuming sulfuric acid at high temperatures. 　　PhH+HO-SO3H——→PhSO3H+H2O Introducing a sulfonic acid group onto the benzene ring reduces its reactivity, making further sulfonation difficult; higher temperatures are required to introduce a second or third sulfonic acid group. This shows that both nitro and sulfonic groups are passivating groups, that is, groups that prevent further electrophilic substitution from occurring. 　　Friedel-Crafts reaction: Under the catalysis of AlCl3, benzene can also react with alcohols, alkenes, and halogenated hydrocarbons; the hydrogen atoms on the benzene ring are replaced by alkyl groups to form alkylbenzenes. This reaction is called an alkylation reaction, also known as the Friedel-Crafts alkylation reaction. For example, the alkylation of ethylene to produce ethylbenzene: PhH+CH2=CH2—AlCl3→Ph-CH2CH3. During this reaction, the R group may undergo rearrangement; for instance, 1-chloropropane reacts with benzene to yield isopropylbenzene, as free radicals always tend toward more stable configurations. 　　Under the catalysis of strong Lewis acids, benzene reacts with acyl chlorides or carboxylic anhydrides; the hydrogen atoms on the benzene ring are replaced by acyl groups to form acylbenzenes. The reaction conditions are similar to those of the alkylation reaction. 　　 Addition reaction Main entry: Addition reaction Although the benzene ring is very stable, it can still undergo addition reactions at double bonds under certain conditions. Typically, through catalytic hydrogenation using nickel as a catalyst, benzene can be converted into cyclohexane. 　　C6H6 + 3H2 → C6H12 Additionally, the reaction that produces hexachlorocyclohexane (BHC) from benzene can take place under ultraviolet light, through the addition of chlorine to benzene. 　　 Oxidation reaction 　　Combustion 　　Benzene, like other hydrocarbons, can burn. When there is an adequate supply of oxygen, the products are carbon dioxide and water. But when burned in air, the flame is bright and produces thick black smoke. This is because the mass fraction of carbon in benzene is high. 　　2C6H6 + 15O2 → 12CO2 + 6H2O 　　Ozonation reaction 　　Benzene can also be oxidized by ozone under certain conditions, with glyoxal as the product. This reaction can be regarded as an ozonation reaction of cyclic polyolefins formed by the localization of the delocalized electrons of benzene. 　　Under normal conditions, benzene cannot be oxidized by strong oxidizing agents. However, in the presence of catalysts such as molybdenum oxide, benzene can be selectively oxidized to maleic anhydride in reaction with oxygen in the air. This is one of the few reactions that can break the six-membered carbon ring of benzene. (Maleic anhydride is a five-membered heterocycle.) ) It is a highly exothermic reaction. 　　 Others: At high temperatures, benzene can undergo a condensation reaction to form biphenyl using iron, copper, or nickel as catalysts. It can form chloro** with formaldehyde and hypochlorous acid in the presence of zinc chloride. Reaction with alkyl metal compounds such as sodium ethylate can yield phenyl metal compounds. Phenyl Grignard reagents can be obtained by reacting magnesium with **furan, chlorobenzene, or bromobenzene**. 　　 Photoisomerization: Benzene can be converted into Dewar benzene under intense light exposure. Dewar benzene is highly reactive; benzene itself is in a stable aromatic state with low energy, while converting it to Dewar benzene requires a large amount of light energy, which results in Dewar benzene having high energy and being unstable. 　　Under laser action, it can be converted into the more reactive rhombane. Rhombane exists in a three-dimensional structure, which results in significant repulsion between the π bonds formed by the sp3 hybridized orbitals of the carbon atoms, making it even less stable. Production 　　Benzene can be obtained through the incomplete combustion of substances with a high carbon content. In nature, both volcanic eruptions and forest fires can produce benzene. Benzene is also present in cigarette smoke. 　　Until World War II, benzene was still a by-product of the coking process in the steel industry. This method can only extract 1 kilogram of benzene from 1 ton of coal. After the 1950s, as industrial demand for benzene increased, particularly from the growing plastic industry, a process for producing benzene from oil was developed. Today, most benzene worldwide comes from the petrochemical industry. The three most important processes for industrial benzene production are catalytic reforming, toluene hydrodealkylation, and steam cracking. 　　 Extracted from coal tar The light tar produced during the coal coking process contains large amounts of benzene. This was the original method for producing benzene. The resulting coal tar and gas are passed together through washing and absorption equipment, using high-boiling-point coal tar as a washing and absorbing agent to recover coal tar from the gas; after distillation, crude benzene and other high-boiling-point fractions are obtained. Industrial-grade benzene can be obtained by refining crude benzene. The purity of benzene obtained by this method is relatively low, it causes severe environmental pollution, and the process is rather outdated. 　　 Extracted from petroleum 　　　 A small amount of benzene is present in crude oil, and extraction of benzene from petroleum products is the most widely used method for its production. 　　Alkane aromatization: Reforming refers here to the process of converting aliphatic hydrocarbons into cyclic structures through dehydrogenation to form aromatic hydrocarbons. This is a technique that developed during World War II. 　　At 500–525°C and 8–50 atmospheres of pressure, various aliphatic hydrocarbons with boiling points between 60–200°C are converted into benzene and other aromatic hydrocarbons through dehydration and cyclization, using a platinum-rhodium catalyst. After the aromatic hydrocarbon products are extracted from the mixture, benzene is separated through distillation. These fractions can also be used as high-octane gasoline. 　　Steam cracking is a process by which olefins are produced from low-molecular-weight alkanes such as ethane, propane, or butane, as well as petroleum components like naphtha and heavy diesel. One of its by-products, pyrolysis gasoline, is rich in benzene, from which benzene and various other components can be distilled out. Pygase can also be mixed with other hydrocarbons as an additive for gasoline. 　　Benzene accounts for about 40-60% of the pyrolysis gasoline; it also contains dienes and other unsaturated compounds such as styrene. These impurities are prone to further reacting during storage to form high-molecular-weight gums. Therefore, a hydrogenation process must first be carried out to remove these impurities and sulfides from the pyrolysis gasoline, followed by appropriate separation to obtain benzene products. 　　 　　 Aromatic separation: The benzene-containing fractions obtained through various methods have very complex compositions, and conventional separation techniques are not effective for dealing with them. Generally, solvent-based liquid-liquid extraction or extractive distillation is used to separate the aromatics, after which conventional separation methods are employed to separate benzene, toluene, and xylene. There are also various separation methods depending on the solvent and technique used. 　　·Udex method: Developed jointly by Dow Chemical Company and UOP in 1950, it initially used diethylene glycol ether as a solvent; later, triethylene glycol ether and tetraethylene glycol ether were used as solvents, with a multouocomer extractor being employed in the process. The yield of benzene was 100%. 　　·Suifolane process: Developed by Shell Netherlands, with the patent held by UOP. Sulfolane is used as the solvent, and a rotary extractor tower is employed for extraction; the product requires treatment with clay. The yield of benzene was 99.9%. 　　·Arosolvan method: Developed in 1962 by the German company Rucho. The solvent is N-methylpyrrolidone (NMP); to increase the yield, 10-20% ethylene glycol ether is sometimes added as well. Using a specially designed Mechnes extractor, the yield of benzene is 99.9%. 　　·IFP method: Developed by the French Institute of Petrochemistry in 1967. Anhydrous dimethyl sulfoxide is used as the solvent, and butane is employed for back-extraction; a rotary tray tower is used in this process. The yield of benzene was 99.9%. 　　·Formex method: Developed in 1971 by the Italian company SNAM and its LRSR oil processing division. Morpholine or N-formylmorpholine is used as the solvent, with a rotary tower. The total yield of aromatic hydrocarbons was 98.8%, with the yield of benzene being 100%. 　　 Toluene dealkylation 　　　 Benzene can be produced by toluene dealkylation through catalytic hydrogenation dealkylation, or via thermal dealkylation without a catalyst. The raw material can be toluene, mixtures of toluene and xylene, or fractions containing benzene as well as other alkyl aromatics and non-aromatics. 　　Toluene catalytic hydrodealkylation: Using catalysts such as chromium, molybdenum, or platinum oxide, toluene mixed with hydrogen can be converted into benzene at high temperatures of 500–600°C and pressures of 40–60 atmospheres; this process is known as hydrodealkylation. If the temperature is higher, the catalyst can be omitted. The reaction proceeds according to the following equation: Ph-CH3 + H2 → PhH + CH4. There are various process methods depending on the catalyst used and the process conditions. · The Hydeal method was developed in 1961 by Ashiand & Refing and UOP company. The raw materials can be reformate, hydrocracked gasoline, toluene, C6–C8 mixed aromatics, dealkylated coal tar, etc. The catalyst is alumina-chromium oxide, the reaction temperature is 600–650°C, and the pressure is 3.43–3.92 MPa. The theoretical yield of benzene is 98%, with a purity of over 99.98%, resulting in a higher quality than benzene produced by the Udex method. 　　·The Detol method, developed by Houdry Company. Alumina and magnesium oxide are used as catalysts, the reaction temperature is 540–650°C, the reaction pressure is 0.69–5.4 MPa, and the raw materials are mainly carbon 7–carbon 9 aromatics. The theoretical yield of benzene is 97%, with a purity that can reach 99.97%. 　　·The Pyrotol method was developed by Air Products and Chemicals and Houdry Company. Suitable for producing benzene from ethylene-derived cracked gasoline. The catalyst is alumina-chromium oxide, the reaction temperature is 600–650°C, and the pressure is 0.49–5.4 MPa. 　　·The Bextol process, developed by Shell. 　　·The BASF process, developed by BASF Corporation. 　　·The Unidak process, developed by UOP. 　　Thermal dealkylation of toluene: Toluene can be dealkylated to produce benzene at high temperatures in a hydrogen stream, without the need for a catalyst. The reaction is exothermic, and various process methods have been developed to address the different problems that arise. 　　·The MHC hydrodealkylation process was developed in 1967 by Mitsubishi Petrochemical Corporation and Chiyoda Construction Company in Japan. The raw material can be pure alkylbenzenes such as toluene, or aromatic fractions containing no more than 30% non-aromatic compounds. The operating temperature is 500–800°C, the operating pressure is 0.98 MPa, and the hydrogen/hydrocarbon ratio is 1–10. Process selectivity: 97–99% (mol), product purity: 99.99%. 　　·The HDA hydrodealkylation process was developed in 1962 by the American companies Hydrocarbon Research and Atlantic Richfield. The raw materials used are toluene, xylene, hydrocracked gasoline, and reformate. The reaction temperature is controlled using hydrogen from different parts of the reactor; it ranges from 600 to 760°C, the pressure is between 3.43 and 6.85 MPa, the hydrogen/hydrocarbon ratio is 1 to 5, and the residence time is 5 to 30 seconds. Selectivity 95%, yield 96-100%. 　　·The Sun process, developed by Sun Oil Company. · The THD process, developed by Gulf Research and Development Company. · The Monsanto process, developed by Monsanto Company. 　　 Toluene disproportionation and transalkylation 　　　As the demand for xylene increased, toluene disproportionation and transalkylation technologies were developed in the late 1960s to increase xylene production simultaneously. (The main reactions are shown in the figure below.) The alkylation reaction is a reversible reaction, and its process varies depending on the catalyst used, process conditions, and raw materials. 　　①① The LTD liquid-phase toluene disproportionation process was developed by Mobil Chemicals in the United States in 1971. It uses non-metallic zeolite or molecular sieve catalysts, with a reaction temperature of 260–315°C. A liquid-phase adiabatic fixed-bed reactor is employed, and toluene serves as the raw material; the conversion rate exceeds 99%.

② The Tatoray process was developed by Toray Industries in Japan and UOP in 1969. Toluene and mixed carbon 9 aromatics are used as raw materials, with mordenite as the catalyst. The reaction temperature ranges from 350–530°C, the pressure is 2.94 MPa, and the hydrogen/hydrocarbon ratio is 5–12. An adiabatic fixed-bed reactor is used, resulting in a single-pass conversion rate of over 40%, a yield of over 95%, and a selectivity of 90%. The product is a mixture of benzene and xylene. 　　The xylene plas process: Developed by the American companies Atlantic Richfield and Engelhard. It uses rare-earth Y-type molecular sieves as catalysts, features a gas-phase moving bed reactor, and operates at a reaction temperature of 471–491°C under normal pressure. 　　③The TOLD process was developed by Mitsubishi Gas Chemical Company in Japan in 1968; it uses a hydrofluoric acid-boron fluoride catalyst, with a reaction temperature of 60–120°C and operates in a low-pressure liquid phase. It is somewhat corrosive. 　　 Other methods 　　In addition, benzene can also be obtained through the polymerization of acetylene, but the yield is very low. Detection methods Gas chromatography and high-performance liquid chromatography can be used to detect the benzene content in various products. The purity of benzene is generally determined using the freezing point method. 　　For the detection of trace amounts of benzene in the air, volatile organic solvents such as methyl silicone oil or low-molecular-weight polymers can be used for absorption, followed by analysis via chromatography ； Or use colorimetry for analysis ； It is also possible to deeply freeze air containing benzene to freeze the benzene, then add ferrous sulfate and hydrogen peroxide solutions to obtain a yellow-brown or black precipitate; this precipitate is subsequently dissolved in nitric acid, followed by analysis using colorimetry. Alternatively, nitric acid can be used to absorb benzene from the air and nitrate it to form m-***benzene, which is then titrated using a titanium dichloride solution; or colorimetric quantification can be carried out using an alkali solution prepared from m-xylene. Industrial uses As early as the 1920s, benzene was already a commonly used solvent in industry, primarily for metal degreasing. Due to the toxicity of benzene, it is no longer used as a solvent in the production processes where solvents come into direct contact with the human body. 　　Benzene can act as an anti-knock agent and thus be used as a gasoline additive. Before the use of tetraethyl lead in the 1950s, all anti-knock agents were benzene. However, now that leaded gasoline is being phased out, benzene has been brought back into use. Due to the adverse effects of benzene on the human body and its contamination of groundwater quality, Europe and the United States **require that the benzene content in gasoline not exceed 1%. 　　The most important industrial use of benzene is as a chemical raw material. Benzene can be used to synthesize a range of benzene derivatives: · Benzene reacts with ethylene to produce ethylbenzene, which can be used to manufacture styrene for plastics ； 　　·Benzene and propylene react to form isopropylbenzene, which can be used in the isopropylbenzene process to produce phenol for making resins and adhesives ； 　　Cyclohexane for producing nylon ； 　　·Synthetic maleic anhydride ； 　　·Used for producing aniline*** ； 　　·Various chlorobenzenes widely used in pesticides ； 　　·Various alkylbenzenes are synthesized for the production of detergents and additives. 　　·Synthesize chemical products such as hydroquinone and anthraquinones. Health hazards 　Due to benzene’s high volatility, it spreads easily when exposed to air. When humans and animals inhale or come into skin contact with large amounts of benzene, it can cause acute and chronic benzene poisoning. Some studies have shown that part of the cause of benzene poisoning is the formation of phenol in the body from benzene. 　　Special attention: (1) Prolonged inhalation can damage the nervous system, while acute poisoning can cause nerve spasms, even coma and death. 　　(2) A large proportion of leukemia patients have a history of exposure to benzene and its derivatives. Is it detailed enough?

The details upstairs are really thorough, hehe, I’ve learned something:victory:

I used to major in organic chemistry. As far as I know, benzene can be used to produce toluene or xylene at specific reaction sites under conditions such as those involving halogens or Grignard reagents; there are likely many details on these conditions available through Scifinder. However, the conditions under which they polymerize are not well understood