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"Arene" redirects here. For other uses, see Arene (disambiguation).

An aromatic hydrocarbon (abbreviated as AH) or arene [1] is a hydrocarbon, of which the molecular structure incorporates one or more planar sets of six carbon atoms that are connected by delocalised electrons numbering the same as if they consisted of alternating single and double covalent bonds. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 In chemistry delocalized electrons are Electrons in a Molecule that are not associated with a single Atom or to a Covalent bond. The term 'aromatic' was assigned before the physical mechanism determining aromaticity was discovered, and was derived from the fact that many of the compounds have a sweet scent. This sweet scent actually came from impurities in the compounds (which are not actually aromatic in the sense initially described). The configuration of six carbon atoms in aromatic compounds is known as a benzene ring, after the simplest possible such hydrocarbon, benzene. Benzene, or benzol, is an organic Chemical compound and a known Carcinogen with the molecular formula C 6 H 6 Benzene, or benzol, is an organic Chemical compound and a known Carcinogen with the molecular formula C 6 H 6 Aromatic hydrocarbons can be monocyclic or polycyclic.

Some non-benzene-based compounds called heteroarenes, which follow Hückel's rule, are also aromatic compounds. In Organic chemistry, Hückel's rule estimates whether a Planar ring Molecule will have Aromatic properties In these compounds, at least one carbon atom is replaced by one of the heteroatoms oxygen, nitrogen, or sulfur. In the nomenclature of Organic chemistry, a heteroatom (from Ancient Greek heteros, different + atomos) is any Atom that Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Examples of non-benzene compounds with aromatic properties are furan, a heterocyclic compound with a five-membered ring that includes an oxygen atom, and pyridine, a heterocyclic compound with a six-membered ring containing one nitrogen atom. Furan, also known as furane and furfuran, is a heterocyclic Organic compound. Pyridine is a Chemical compound with the formula C5[[Hydrogen H5]] N. [2]

Contents

Benzene ring model

Benzene
Benzene
Main article: aromaticity

Benzene, C6H6, is the simplest AH and was recognized as the first aromatic hydrocarbon, with the nature of its bonding first being recognized by Friedrich August Kekulé von Stradonitz in the 19th century. Benzene, or benzol, is an organic Chemical compound and a known Carcinogen with the molecular formula C 6 H 6 Benzene, or benzol, is an organic Chemical compound and a known Carcinogen with the molecular formula C 6 H 6 Friedrich August Kekule von Stradonitz (also August Kekulé) (7 September 1829 &ndash 13 July 1896 was a German organic chemist. Each carbon atom in the hexagonal cycle has four electrons to share. One goes to the hydrogen atom, and one each to the two neighboring carbons. This leaves one to share with one of its two neighboring carbon atoms, which is why the benzene molecule is drawn with alternating single and double bonds around the hexagon.

Many chemists draw a circle around the inside of the ring to show six electrons floating around in delocalized molecular orbitals the size of the ring itself. This also accurately represents the equivalent nature of the six bonds all of bond order ~1. Bond order is the number of bonds between a pair of atoms For example in Nitrogen N≡N the bond order is 3 in Acetylene H−C≡C−H the bond order between the 5. This equivalency is well explained by resonance forms. Resonance in Chemistry is a theory used to represent and model certain types of non-classical Molecular structures Resonance is a key component The electrons float above and below the ring, and the electromagnetic fields they generate keep the ring flat. General properties:

  1. Display aromaticity.
  2. The Carbon-Hydrogen ratio is very large.
  3. They burn with a sooty yellow flame because of the high carbon-hydrogen ratio.
  4. They undergo electrophilic substitution reactions and nucleophilic aromatic substitutions. Electrophilic aromatic substitution or EAS is an Organic reaction in which an atom usually Hydrogen, appended to an aromatic system is replaced nucleophilic aromatic substitution is a Substitution reaction in Organic chemistry in which the Nucleophile displaces a good Leaving group,

Arene synthesis

Many laboratory methods exist for the organic synthesis of arenes from non-arene precursors:

Arene reactions

The main arene reactions are

Lesser-known reactions:

Benzene and derivatives of benzene

Toluene
Toluene

Benzene derivatives have from one to six substituents attached to the central benzene core. Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of In Organic chemistry, a substituent is an atom or group of atoms substituted in place of a Hydrogen atom on the Parent chain of a Hydrocarbon Examples of benzene compounds with just one substituent are phenol, which carries a hydroxyl group and toluene with a methyl group. Phenol, is a toxic colourless Crystalline Solid with a sweet tarry odor commonly referred to as a "hospital smell" Hydroxyl in Chemistry stands for a molecule consisting of an Oxygen atom and a Hydrogen atom connected by a Covalent bond. Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of In Chemistry, a methyl group is a Hydrophobic Alkyl Functional group named after Methane (4 When there is more than one substituent present on the ring, their spatial relationship becomes important for which the arene substitution patterns ortho, meta, and para are devised. Arene substitution patterns are part of Organic chemistry IUPAC nomenclature and pinpoint the position of Substituents other than Hydrogen in For example, three isomers exist for cresol because the methyl group and the hydroxyl group can be placed next to each other (ortho), one position removed from each other (meta), or two positions removed from each other (para). This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. Cresols are Organic compounds which are methyl[[phenol]]s They are a widely occurring natural and manufactured group of Aromatic Organic compounds Xylenol has two methyl groups in addition to the hydroxyl group, and, for this structure, 6 isomers exist. Xylenol or dimethylphenol is an Arene compound with two Methyl groups and a Hydroxyl group

Examples of benzene derivatives with alkyl substituents (alkylbenzenes):

Examples of other aromatic compounds:

The arene ring has an ability to stabilize charges. Ethylbenzene is an Organic compound with the formula C6H5CH2CH3 Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of o-Xylene|m-Xylene|p-XyleneThe term xylene or xylol refers to a mixture of three Benzene derivatives which is used as a Solvent in the Printing m -Xylene is an Aromatic Hydrocarbon, based on Benzene with two Methyl Substituents It is an isomer of ''o''-xylene p -Xylene is an Aromatic hydrocarbon, based on Benzene with two Methyl Substituents The “p” stands for para, identifying In Organic chemistry, mesitylene or 135-trimethylbenzene (C9H12 is an Aromatic hydrocarbon with three Methyl Durene, or 1245-tetramethylbenzene, is an Aromatic Hydrocarbon used as a Solvent. Aniline, phenylamine or aminobenzene is an Organic compound with the formula C6H7N Aspirin, or acetylsalicylic acid (ASA (əˌsɛtɨlsælɨˌsɪlɨk ˈæsɨd is a Salicylate drug, often used as an Analgesic to relieve Benzoic acid, C7H6O2 (or C6H5COOH is a colorless crystalline solid and the simplest Aromatic Carboxylic acid Biphenyl (or diphenyl or phenyl benzene or 11'-biphenyl or lemonene) is a solid Organic compound that forms colorless to yellowish crystals Chlorobenzene is an Aromatic Organic compound with the chemical formula C6H5Cl Nitrobenzene, also known as nitrobenzol or oil of mirbane, is an Organic compound with the Chemical formula C 6 Paracetamol ( INN) (ˌpærəˈsiːtəmɒl -ˈsɛtə- or acetaminophen ( USAN) is a widely-used Analgesic and Antipyretic Medication Phenacetin, introduced in 1887 was used principally as an Analgesic, and was one of the first synthetic fever reducers to go on the market Phenol, is a toxic colourless Crystalline Solid with a sweet tarry odor commonly referred to as a "hospital smell" "TNP" redirects here For the airport with the IATA airport code TNP see Twentynine Palms Airport. Salicylic acid (from the Latin word for the willow tree Salix, from whose bark it can be obtained is a Beta hydroxy acid (BHA with the formula Trinitrotoluene ( TNT) is a Chemical compound with the formula C6H2(NO23CH3 This is seen in, for example, phenol (C6H5-OH), which is acidic at the hydroxyl (OH), since a charge on this oxygen (alkoxide -O–) is partially delocalized into the benzene ring. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are

Polyaromatic hydrocarbons

Main article: Polycyclic aromatic hydrocarbon
Naphthalene
Naphthalene

Some important arenes are the polyaromatic hydrocarbons (PAH); they are also called polycyclic aromatic hydrocarbons and polynuclear aromatic hydrocarbons. Polycyclic aromatic hydrocarbons ( PAH s are Chemical compounds that consist of fused Aromatic rings and do not contain Heteroatoms or Naphthalene, also known as naphthalin, naphthaline, tar camphor, white tar, albocarbon, or antimite and not to be They are composed of more than one aromatic ring. The simplest PAHs are benzocyclopropene (C7H6), benzocyclopropane (C7H8), benzocyclobutadiene (C8H6), and benzocyclobutene (C8H8). Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Benzocyclobutadiene is the simplest Polycyclic aromatic hydrocarbon, being composed of a Benzene ring fused to a Cyclobutene ring Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Benzocyclobutene ( BCB) is a Benzene ring fused to a Cyclobutane ring Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1

Common examples are naphthalene with two fused rings, anthracene with three, tetracene with four, and pentacene with five linearly fused rings. Naphthalene, also known as naphthalin, naphthaline, tar camphor, white tar, albocarbon, or antimite and not to be Anthracene is a solid Polycyclic aromatic hydrocarbon consisting of three fused Benzene rings derived from Coal-tar. Tetracene, also called naphthacene, benzanthracene and 23-benzanthracene, is a Polycyclic aromatic hydrocarbon. Pentacene is a Polycyclic aromatic hydrocarbon consisting of 5 linearly-fused Benzene rings Phenanthrene and triphenylene are examples of non-linear connections. Phenanthrene is a Polycyclic aromatic hydrocarbon composed of three fused Benzene rings In Chemistry, the Organic compound triphenylene is a flat Polycyclic aromatic hydrocarbon (PAH consisting of four fused Benzene rings More exotic examples are helicenes and corannulene. Helicenes in Organic chemistry are ortho-condensed Polycyclic aromatic compounds in which benzene rings or other aromatic compounds Corannulene is a Polycyclic aromatic hydrocarbon with Chemical formula C 20 H 10

These compounds are one of the most widespread organic pollutants, remaining on beaches and marine environmentals for a long time after an oil spill. Persistent organic pollutants ( POP s are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic For the fictional character see Oil Slick (Transformers. An oil spill is the release of a Liquid Petroleum Hydrocarbon into Recent investigations have concluced that their toxicity is up to 100 times worse than first assumed. [4]

See also

External links

References

  1. ^ Definition IUPAC Gold Book Link
  2. ^ HighBeam Encyclopedia: aromatic compound
  3. ^ Jerry March Advanced Organic Chemistry 3Ed. Compendium of Chemical Terminology (ISBN 0-86542-684-8 is a book published by IUPAC containing internationally accepted definitions for terms in Chemistry. , ISBN 0-471-85472-7
  4. ^ Sound battles back, but threats linger. NOAA Fisheries. Retrieved on 2008-02-02. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 962 - Translatio imperii: Pope John XII crowns Otto I Holy Roman Emperor, the first Holy Roman Emperor
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