aromatic hydrocarbon

Examples of aromatic hydrocarbon in the following topics:

• Polycyclic Aromatic Hydrocarbons

  • Polycyclic aromatic hydrocarbons are potent atmospheric pollutants that consist of fused aromatic rings and do not contain heteroatoms.
  • It can degrade high molecular mass polycyclic aromatic hydrocarbons of 4 and 5 rings.
  • Polycyclic aromatic hydrocarbons (PAHs), also known as poly-aromatic hydrocarbons or polynuclear aromatic hydrocarbons, are seen in .
  • It can degrade high molecular mass polycyclic aromatic hydrocarbons of 4 and 5 rings.
  • An image showing three examples of polycyclic aromatic hydrocarbons.

• Introduction to Hydrocarbons

  • This class can be further divided into two groups: aliphatic hydrocarbons and aromatic hydrocarbons.
  • Aromatic hydrocarbons, or arenes, which contain a benzene ring, were originally named for their pleasant odors.
  • For example, a chemical structure can be both aromatic and contain an alkyne.
  • The study of hydrocarbons is particularly important to the fields of chemical and petroleum engineering, as a variety of hydrocarbons can be found in crude oil.
  • The benzene molecules and its derivatives are the basis for aromatic structures.

• Properties of Aromatic Compounds

  • Aromatic compounds, originally named because of their fragrant properties, are unsaturated hydrocarbon ring structures that exhibit special properties, including unusual stability, due to their aromaticity.
  • Aromatic compounds are generally nonpolar and immiscible with water.
  • This stability is lost in electrophilic addition because the product is not aromatic.
  • Aromatic compounds are produced from a variety of sources, including petroleum and coal tar.
  • Poly-aromatic hydrocarbons are components of atmospheric pollution and are known carcinogens.

• Hydrocarbons

  • Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen, such as methane (CH4).
  • Hydrocarbons are often used as fuels: the propane in a gas grill or the butane in a lighter.
  • The hydrocarbons discussed so far have been aliphatic hydrocarbons, which consist of linear chains of carbon atoms.
  • Another type of hydrocarbon, aromatic hydrocarbons, consists of closed rings of carbon atoms.
  • Some hydrocarbons have both aliphatic and aromatic portions; beta-carotene is an example of such a hydrocarbon.

• Other Aromatic Compounds

  • Benzene is the archetypical aromatic compound.
  • Four illustrative examples of aromatic compounds are shown above.
  • The first example is azulene, a blue-colored 10 π-electron aromatic hydrocarbon isomeric with naphthalene.
  • Remarkably, this hydrocarbon is chemically unstable, in contrast to most other aromatic hydrocarbons.
  • Formulation of the Hückel rule prompted organic chemists to consider the possible aromaticity of many unusual unsaturated hydrocarbons.

• Antiaromaticity

  • Conjugated ring systems having 4n π-electrons (e.g. 4, 8, 12 etc. electrons) not only fail to show any aromatic properties, but appear to be less stable and more reactive than expected.
  • Examples of 8 and 12-π-electron systems are shown below, together with a similar 10 π-electron aromatic compound.
  • The simple C8H6 hydrocarbon pentalene does not exist as a stable compound, and its hexaphenyl derivative is air sensitive.
  • On the other hand, azulene is a stable 10-π-electron hydrocarbon that incorporates structural features of both pentalene and heptalene.
  • Azulene is a stable blue crystalline solid that undergoes a number of typical aromatic substitution reactions.

• Substitution Reactions of Benzene and Other Aromatic Compounds

  • The remarkable stability of the unsaturated hydrocarbon benzene has been discussed in an earlier section.
  • Since the reagents and conditions employed in these reactions are electrophilic, these reactions are commonly referred to as Electrophilic Aromatic Substitution.

• Anoxic Hydrocarbon Oxidation

  • Anoxic hydrocarbon oxidation can be used to degrade toxic hydrocarbons, such as crude oil, in anaerobic environments.
  • Hydrocarbons are organic compounds consisting entirely of hydrogen and carbon.
  • Crude oil contains aromatic compounds that are toxic to most forms of life.
  • Although it was once thought that hydrocarbon compounds could only be degraded in the presence of oxygen, the discovery of anaerobic hydrocarbon-degrading bacteria and pathways show that the anaerobic degradation of hydrocarbons occurs naturally.
  • Microbes may be used to degrade toxic hydrocarbons in anaerobic environments.

• Prokaryotes and Environmental Bioremediation

  • Hydrocarbon-degrading bacteria feed on hydrocarbons in the oil droplet, breaking down the hydrocarbons.
  • In addition to naturally occurring oil-degrading bacteria, humans select and engineer bacteria that possess the same capability with increased efficacy and the spectrum of hydrocarbon compounds that can be processed.
  • Other oil fractions containing aromatic and highly-branched hydrocarbon chains are more difficult to remove and remain in the environment for longer periods of time.

• Benzene and other Aromatic Compounds

  • The adjective "aromatic" is used by organic chemists in a rather different way than it is normally applied.
  • Benzoic acid was eventually converted to the stable hydrocarbon benzene, C6H6, which also proved unreactive to common double bond transformations, as shown below.
  • As experimental evidence for a wide assortment of compounds was acquired, those incorporating this exceptionally stable six-carbon core came to be called "aromatic".
  • This sort of stability enhancement is now accepted as a characteristic of all aromatic compounds.
  • A molecular orbital description of benzene provides a more satisfying and more general treatment of "aromaticity".