Hexacene is an
aromatic
In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...
compound consisting of six linearly-fused benzene rings. It is a blue-green, air-stable solid with low solubility.
[
Hexacene is one of a series of linear polycyclic molecules created by such aromatic ring fusions, a series termed ]acene
In organic chemistry, the acenes or polyacenes are a class of organic compounds and polycyclic aromatic hydrocarbons made up of benzene () rings which have been linearly fused. They follow the general molecular formula .
The larger represent ...
s; the previous in the series is pentacene
Pentacene () is a polycyclic aromatic hydrocarbon consisting of five linearly-fused benzene () rings. This highly conjugated compound is an organic semiconductor. The compound generates excitons upon absorption of ultra-violet ( UV) or visible ...
(with five fused rings) and the next is heptacene
Heptacene is an organic compound and a polycyclic aromatic hydrocarbon and the seventh member of the acene or polyacene family of linear fused benzene rings. This compound has long been pursued by chemists because of its potential interest in elec ...
(with seven). It and other acenes and their derivatives have been investigated in potential applications related to organic semiconductor
Organic semiconductors are solids whose building blocks are pi-bonded molecules or polymers made up by carbon and hydrogen atoms and – at times – heteroatoms such as nitrogen, sulfur and oxygen. They exist in the form of molecular crystals o ...
s. Like larger acenes, hexacene is poorly soluble, but derivatives have been prepared with improved solubility, such as 6,15-Bis(tri-t-butylsilylethynyl)hexacene, which melts with decomposition at 96 °C.
Syntheses and structure
Hexacene has been the subject of many syntheses. One route uses thermal decarbonylation
In chemistry, decarbonylation is a type of organic reaction that involves the loss of carbon monoxide (CO). It is often an undesirable reaction, since it represents a degradation. In the chemistry of metal carbonyls, decarbonylation describes a ...
of a monoketone precursor.
Further reading
*First synthesis:
**Marschalk, C. Linear hexacenes. Bull. Soc. Chim. Fr. 6, 1112–1121 (1939).
**
**
*By dehydrogenation
In chemistry, dehydrogenation is a chemical reaction that involves the removal of hydrogen, usually from an organic molecule. It is the reverse of hydrogenation. Dehydrogenation is important, both as a useful reaction and a serious problem. At ...
of ''hexacosahydrohexacene'' by palladium on carbon
Palladium on carbon, often referred to as Pd/C, is a form of palladium used as a catalyst. The metal is supported on activated carbon to maximize its surface area and activity.
Uses Hydrogenation
Palladium on carbon is used for catalytic hydrog ...
*Isolation:
*By decarbonylation of a diketone
In organic chemistry, a dicarbonyl is a molecule containing two carbonyl () groups. Although this term could refer to any organic compound containing two carbonyl groups, it is used more specifically to describe molecules in which both carbonyls ...
precursor:
*Deoxygenation route:
External links
Molecular graphics representation of the X-ray crystallographic structure determined for 6,15-bis(tri-t-butylsilylethynyl)hexacene
€”hexacene with bulky, protective substituents in the reactive 6- and 15- ring positions, see rotating graphic at base of page.
Sander-Wise Polycyclic Aromatic Hydrocarbon Structure Index entry for hexacene
NIST Special Publication 922.
References
{{PAHs
Organic semiconductors
Acenes
Polycyclic aromatic hydrocarbons
Hexacyclic compounds