anthracene

[an-thruh-seen]

anthracene, C₁₄H₁₀, solid organic compound derived from coal tar. It melts at 218°C; and boils at 354°C;. When pure it is colorless and has a violet fluorescence; it darkens when exposed to sunlight. Anthracene is insoluble in water but is quite soluble in carbon disulfide and somewhat soluble in ethanol, methanol, benzene, chloroform, and other organic solvents. It is readily oxidized to form anthraquinone, the parent compound of the alizarin series of dyes. The molecular structure of anthracene consists of three benzenelike rings joined side by side; it is thus an aromatic compound. It is the first member of the anthracene series, a group of aromatic hydrocarbons that are structurally related to it and have the general formula C_nH_2n-18.

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Anthracene

Anthracene is a solid polycyclic aromatic hydrocarbon consisting of three fused benzene rings derived from coal-tar. Anthracene is used in the artificial production of the red dye alizarin. It is also used in wood preservatives, insecticides, and coating materials. Anthracene is colorless but exhibits a blue (400-500 nm peak) fluorescence under ultraviolet light.

Synthesis

A classic method for the preparation of anthracene in the laboratory is by cyclodehydration of o-methyl- or o-methylene-substituted diarylketones in the so-called Elbs reaction (named for the German chemist Karl Elbs).

Reactions

Anthracene has the ability to photodimerize with irradiation by UV light. This results in considerable changes in the physical properties of the material.

The dimer is connected by two covalent bonds resulting from the [4+4] cycloaddition. The dimer reverts to anthracene thermally or with UV irradiation below 300 nm. The reversible bonding and photochromic properties of anthracenes is the basis of many potential applications using poly and monosubstituted anthracene derivatives. The reaction is sensitive to oxygen.

In most other reactions of anthracene, the central ring is also targeted, as it is the most highly reactive. Electrophilic substitution occurs at the "9" and "10" positions of the center ring, and oxidation of anthracene occurs readily, giving anthraquinone, C₁₄H₈O₂ (below).

Uses

Anthracene can also have a hydroxyl group to form 1-hydroxyanthracene and 2-hydroxyanthracene, homologous to phenol and napthol, and hydroxyanthracene is also called anthrol, and anthracenol. Hydroxyanthracene derivatives are pharmacologically active, and are contained in aloe for example.

Anthracene is an organic semiconductor. It is used as a scintillator for detectors of high energy photons, electrons and alpha particles. Plastics such as polyvinyltoluene can be doped with anthracene to produce a plastic scintillator that is approximately water equivalent for use in radiation therapy dosimetry. Anthracene's emission spectrum peaks at between 400 nm and 440 nm.

Bipedal derivative

In 2005, chemists at the University of California, Riverside developed the first bipedal molecule, 9,10-Dithioanthracene, which propels itself in a straight line when heated on a flat copper surface. Researchers believe the molecule has potential for use in molecular computers.