Dibenzo[de,mn]naphthacene or zethrene is an aromatic hydrocarbon

Aromatic hydrocarbon

An aromatic hydrocarbon or arene is a hydrocarbon with alternating double and single bonds between carbon atoms. 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...

 consisting of two phenalene

Phenalene

Phenalene is a polycyclic aromatic hydrocarbon . Like many PAHs, it is an atmospheric pollutant formed during the combustion of fossil fuels....

 units fused together. According to Clar's rule the two exterior naphtalene units are truly aromatic and the two central double bonds

Alkene

In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...

 are not aromatic at all. For this reason the compound is of some interest to academic research. Zethrene is air and light sensitive (complete decomposition under a sunlight lamp within 12 hours) with a deep-red color. The melting point

Melting point

The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

 is 262 °C.

Synthesis

The compound was first synthesised by Erich Clar in 1955 from acenaphthene

Acenaphthene

Acenaphthene is a polycyclic aromatic hydrocarbon consisting of naphthalene with an ethylene bridge connecting positions 1 and 8. An alternative name, 1,2-dihydroacenaphthylene, emphasizes that it is a hydrogenated form of acenaphthylene...

 in one method and from chrysene

Chrysene

Chrysene is a polycyclic aromatic hydrocarbon with the molecular formula that consists of four fused benzene rings. It is a natural constituent of coal tar, from which it was first isolated and characterized...

 in another. Mitchell & Sondheimer prepared the compound from a benzannulated [10]annulene

Cyclodecapentaene

Cyclodecapentaene or [10]annulene is an annulene with molecular formula C10H10. This organic compound is a conjugated 10 pi electron cyclic system and according to Huckel's rule it should display aromaticity. It is not aromatic, however, because of a combination of steric strain and angular strain...

.

Zethrene synthesis 1968 Sondheimer

A sulfur extrusion method was reported by Kemp, Storie & Tulloch. Wu et al. reported the synthesis of the compound in a coupling reaction

Coupling reaction

A coupling reaction in organic chemistry is a catch-all term for a variety of reactions where two hydrocarbon fragments are coupled with the aid of a metal catalyst...

 / dimerization with in-situ desilylization.

Zethrene synthesis Wu 2010

Derivatives are also known.

Structure

X-ray crystallography

X-ray crystallography

X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...

indicates that zethrene is a planar molecule. The bond lengths in the central part of the molecule are consistent with distinct single and double bonds rather than aromatic components.