Alkylbenzene

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Toluene (or methylbenzene) is a common chemical found in chemistry laboratories. Bottle of Toluene.jpg
Toluene (or methylbenzene) is a common chemical found in chemistry laboratories.

An alkylbenzene is a chemical compound that contains a monocyclic aromatic ring attaching to one or more saturated hydrocarbon chains. [1] Alkylbenzenes are derivatives of benzene, in which one or more hydrogen atoms are replaced by alkyl groups. The simplest member, toluene (or methylbenzene), has the hydrogen atom of the benzene ring replaced by a methyl group. The chemical formula of alkylbenzenes is CnH2n-6. [2]

Contents

Safety hazards of toluene. Oftentimes, toluene is used as an organic solvent. Safety Hazard of Toluene.jpg
Safety hazards of toluene. Oftentimes, toluene is used as an organic solvent.

Alkylbenzenes are a very important class of hydrocarbons, especially in the synthetic production industry. It is the raw material in the production of synthetic sulfonate detergents, which are found in a variety of household products such as soap, shampoo, toothpaste, laundry detergent, etc. Linear alkylbenzenes (LAB) and branched alkylbenzenes (BAB) are families of alkylbenzene used to prepare synthetic sulfonates. However, LABs are more industrially favoured since the discovery of its extensive biodegradable yield over BAB-based sulfonates in the 1960s. [3]

Examples of alkylbenzenes

Parent compound:

Benzene

Alkylbenzenes
Benzol.svg Benzene Toluol.svg Toluene
Xylenes
Ortho-Xylol - ortho-xylene 2.svg o-xylene Meta-Xylol - meta-xylene 2.svg m-xylene Para-Xylol - para-xylene 2.svg p-xylene
Trimethylbenzenes
Hemimellitene.svg hemimellitene Pseudocumene.svg pseudocumene Mesitylen.svg mesitylene
Tetramethylbenzenes
1,2,3,4-Tetramethylbenzol.svg prehnitene 1,3,4,5-Tetramethylbenzol.svg isodurene 1,2,4,5-Tetramethylbenzol.svg durene
Miscellaneous
Ethylbenzol.svg Ethylbenzene Cumol.svg Cumene P-Cymol.svg p-Cymene
Xylene isomers are also used as solvents in laboratories. Note that in the photo, o-xylene, not being stored in a brown glass bottle, appears to have auto-oxidized. Xylenes isomers.jpg
Xylene isomers are also used as solvents in laboratories. Note that in the photo, o-xylene, not being stored in a brown glass bottle, appears to have auto-oxidized.

Reactions

Spectroscopy

Alkylbenzene isomers can be differentiated by observing the position of alkyl substituents on the benzene ring using chemical ionization-proton exchange mass spectrometry. Conventional GC-MS yields limited results because the isomers have identical molecular weight and substituents. [6]

Production

Some alkylbenzenes such as toluene, trimethylbenzenes, and tetramethylbenzenes occur naturally in coal tar oil and as byproducts of the crude oil refinery process. Others can be prepared by Friedel-Crafts alkylation. [3]

Alkylbenzenes used to be synthesized from tetrapropylene, however, the reaction is now rarely used because of the low biodegradable alkylbenzene sulfonates it yields. [3]

Safety hazards

Alkylbenzenes are flammable. Most of them are eye and skin irritants and pose an acute health hazard when ingested. Alkylbenzenes are toxic to aquatic life with long-lasting effects.

Application

Synthetic sulfonates

Alkylbenzenes are the primary raw material in making synthetic alkylbenzene sulfonates. Synthetic sulfonates are the most widely used detergents, as industrial oil, emulsifiers, demulsifiers, rust inhibitors, dispersants, surfactants for enhanced oil recovery, ore-floatation agents, and wetting agents, among others. LABs such as alkylbenzene, dialkylbenzene, and alkyltoluene are most commonly used to prepare sulfonate detergents. [4]

Solvent use

Some less substituted alkylbenzenes such as toluene and xylene are commonly used as solvents industrially.

Literature

Related Research Articles

<span class="mw-page-title-main">Petrochemical</span> Chemical product derived from petroleum

Petrochemicals are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as maize, palm fruit or sugar cane.

<span class="mw-page-title-main">Detergent</span> Surfactants with cleansing properties

A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more soluble in hard water, because the polar sulfonate is less likely than the polar carboxylate to bind to calcium and other ions found in hard water.

The Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring. Friedel–Crafts reactions are of two main types: alkylation reactions and acylation reactions. Both proceed by electrophilic aromatic substitution.

<span class="mw-page-title-main">Alkylation</span> Transfer of an alkyl group from one molecule to another

Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene. Alkylating agents are reagents for effecting alkylation. Alkyl groups can also be removed in a process known as dealkylation. Alkylating agents are often classified according to their nucleophilic or electrophilic character. In oil refining contexts, alkylation refers to a particular alkylation of isobutane with olefins. For upgrading of petroleum, alkylation produces a premium blending stock for gasoline. In medicine, alkylation of DNA is used in chemotherapy to damage the DNA of cancer cells. Alkylation is accomplished with the class of drugs called alkylating antineoplastic agents.

In organic chemistry, an aryl halide is an aromatic compound in which one or more hydrogen atoms, directly bonded to an aromatic ring are replaced by a halide. The haloarene are different from haloalkanes because they exhibit many differences in methods of preparation and properties. The most important members are the aryl chlorides, but the class of compounds is so broad that there are many derivatives and applications.

<span class="mw-page-title-main">Sulfonic acid</span> Organic compounds with the structure R−S(=O)2−OH

In organic chemistry, sulfonic acid refers to a member of the class of organosulfur compounds with the general formula R−S(=O)2−OH, where R is an organic alkyl or aryl group and the S(=O)2(OH) group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound is the parent sulfonic acid, HS(=O)2(OH), a tautomer of sulfurous acid, S(=O)(OH)2. Salts or esters of sulfonic acids are called sulfonates.

<span class="mw-page-title-main">Aromatic sulfonation</span>

Aromatic sulfonation is an organic reaction in which a hydrogen atom on an arene is replaced by a sulfonic acid functional group in an electrophilic aromatic substitution. Aryl sulfonic acids are used as detergents, dye, and drugs.

Polysulfones are a family of high performance thermoplastics. These polymers are known for their toughness and stability at high temperatures. Technically used polysulfones contain an aryl-SO2-aryl subunit. Due to the high cost of raw materials and processing, polysulfones are used in specialty applications and often are a superior replacement for polycarbonates.

p-Cymene is a naturally occurring aromatic organic compound. It is classified as an alkylbenzene related to a monoterpene. Its structure consists of a benzene ring para-substituted with a methyl group and an isopropyl group. p-Cymene is insoluble in water, but miscible with organic solvents.

Chlorotoluene is a group of three isomeric chemical compounds. They consist of a disubstituted benzene ring with one chlorine atom and one methyl group.

<span class="mw-page-title-main">Hydrazines</span> Class of chemical compounds

Hydrazines (R2N−NR2) are a class of chemical compounds with two nitrogen atoms linked via a covalent bond and which carry from one up to four alkyl or aryl substituents. Hydrazines can be considered as derivatives of the inorganic hydrazine (H2N−NH2), in which one or more hydrogen atoms have been replaced by hydrocarbon groups.

<span class="mw-page-title-main">Durene</span> Chemical compound

Durene, or 1,2,4,5-tetramethylbenzene, is an organic compound with the formula C6H2(CH3)4. It is a colourless solid with a sweet odor. The compound is classified as an alkylbenzene. It is one of three isomers of tetramethylbenzene, the other two being prehnitene (1,2,3,4-tetramethylbenzene) and isodurene (1,2,3,5-tetramethylbenzene). Durene has an unusually high melting point (79.2 °C), reflecting its high molecular symmetry.

<span class="mw-page-title-main">Benzene</span> Hydrocarbon compound consisting of a 6-sided ring

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.

In organic chemistry, transalkylation is a chemical reaction involving the transfer of an alkyl group from one organic compound to another. The reaction is used for the transfer of methyl and ethyl groups between benzene rings. This is of particular value in the petrochemical industry to manufacture p-xylene, styrene, and other aromatic compounds. Motivation for using transalkylation reactions is based on a difference in production and demand for benzene, toluene, and xylenes. Transalkylation can convert toluene, which is overproduced, into benzene and xylene, which are under-produced. Zeolites are often used as catalysts in transalkylation reactions.

<span class="mw-page-title-main">Alkylbenzene sulfonate</span> Class of chemical compounds

Alkylbenzene sulfonates are a class of anionic surfactants, consisting of a hydrophilic sulfonate head-group and a hydrophobic alkylbenzene tail-group. Along with sodium laureth sulfate, they are one of the oldest and most widely used synthetic detergents and may be found in numerous personal-care products and household-care products . They were introduced in the 1930s in the form of branched alkylbenzene sulfonates (BAS). However following environmental concerns these were replaced with linear alkylbenzene sulfonates (LAS) during the 1960s. Since then production has increased significantly from about one million tons in 1980, to around 3.5 million tons in 2016, making them most produced anionic surfactant after soaps.

<span class="mw-page-title-main">Alkynol</span> Type of organic chemical compound

In organic chemistry, alkynols (hydroxyalkynes) are organic compounds that contain both alkyne and alcohol functional groups. Thus, as structural features, they have a C≡C triple bond and a hydroxyl group. Some alkynols play a role as intermediates in the chemical industry.

<span class="mw-page-title-main">Benzyl iodide</span> Chemical compound

Benzyl iodide is an organic compound with the chemical formula C
7
H
7
I
. The compound consists of a benzene ring with an attached iodidemethyl group. The substance is an alkyl halide and is a constitutional isomer of the iodotoluenes.

<span class="mw-page-title-main">Photochlorination</span>

Photochlorination is a chlorination reaction that is initiated by light. Usually a C-H bond is converted to a C-Cl bond. Photochlorination is carried out on an industrial scale. The process is exothermic and proceeds as a chain reaction initiated by the homolytic cleavage of molecular chlorine into chlorine radicals by ultraviolet radiation. Many chlorinated solvents are produced in this way.

<i>o</i>-Cymene Organic compound

o-Cymene is an organic compound classified as an aromatic hydrocarbon. Its structure consists of a benzene ring ortho-substituted with a methyl group and an isopropyl group. It is a flammable colorless liquid which is nearly insoluble in water but soluble in organic solvents.

<i>m</i>-Cymene Organic compound

m-Cymene is an organic compound classified as an aromatic hydrocarbon. Its structure consists of a benzene ring meta-substituted with a methyl group and an isopropyl group. It is a flammable colorless liquid which is nearly insoluble in water but soluble in organic solvents.

References

  1. Francis, Alfred W. (1948-02-01). "Properties of Alkylbenzenes". Chemical Reviews. 42 (1): 107–162. doi:10.1021/cr60131a003. ISSN   0009-2665. PMID   18904921.
  2. Sazhin, S. S. (2022). Droplets and sprays : simple models of complex processes. Cham, Switzerland: Springer. ISBN   978-3-030-99746-5. OCLC   1333919856.
  3. 1 2 3 Griesbaum, Karl; Behr, Arno; Biedenkapp, Dieter; Voges, Heinz-Werner; Garbe, Dorothea; Paetz, Christian; Collin, Gerd; Mayer, Dieter; Höke, Hartmut (2013-09-16), "Hydrocarbons", in Wiley-VCH Verlag GmbH & Co. KGaA (ed.), Ullmann's Encyclopedia of Industrial Chemistry, Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, pp. 1–61, doi:10.1002/14356007.a13_227.pub2, ISBN   978-3-527-30673-2, S2CID   242394133 , retrieved 2023-04-12
  4. 1 2 3 Lubricant additives : chemistry and applications. Leslie R. Rudnick. [Place of publication not identified]. 2017. ISBN   978-1-351-64696-3. OCLC   1003859957.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)
  5. De, Surya K. (2021-01-26). Applied Organic Chemistry: Reaction Mechanisms and Experimental Procedures in Medicinal Chemistry (1 ed.). Wiley. doi:10.1002/9783527828166.ch5. ISBN   978-3-527-34785-8. S2CID   242435919.
  6. Hawthorne, Steven B.; Miller, David J. (1985-03-01). "Identifying alkylbenzene isomers with chemical ionization-proton exchange mass spectrometry". Analytical Chemistry. 57 (3): 694–698. doi:10.1021/ac00280a027. ISSN   0003-2700.

References