|Molar mass||178.23 g·mol−1|
|Melting point||101 °C (214 °F; 374 K)|
|Boiling point||332 °C (630 °F; 605 K)|
|Flash point||171 °C (340 °F; 444 K)|
|Dipole moment||0 D|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Phenanthrene is a polycyclic aromatic hydrocarbon composed of three fused benzene rings. The name phenanthrene is a composite of phenyl and anthracene. In its pure form, it is found in cigarette smoke and is a known irritant, photosensitizing skin to light. Phenanthrene appears as a white powder having blue fluorescence.
The compound with a phenanthrene skeleton and nitrogens at the 4 and 5 positions is known as phenanthroline.
A classical phenanthrene synthesis is the Bardhan–Sengupta phenanthrene synthesis.
The first step is an electrophilic aromatic substitution reaction, which is allowed when the diphosphorus pentoxide makes the alcohol a better leaving group. However, no alkenes outside of the initial aromatic ring are created. In the second step of this reaction 9,10-dihydrophenanthrene is oxidized with elemental selenium. The aromatization of six-membered rings by selenium is not clearly understood, but it does produce H2Se.
Phenanthrene can also be obtained photochemically from certain diarylethenes.
Reactions of phenanthrene typically occur at the 9 and 10 positions, including:
- Organic oxidation to phenanthrenequinone with chromic acid
- Organic reduction to 9,10-dihydrophenanthrene with hydrogen gas and raney nickel
- Electrophilic halogenation to 9-bromophenanthrene with bromine
- Aromatic sulfonation to 2 and 3-phenanthrenesulfonic acids with sulfuric acid
- Ozonolysis to diphenylaldehyde
Phenanthrene is more stable than its linear isomer anthracene. A classic and well established explanation is based on Clar's rule. A novel theory invokes so-called stabilizing hydrogen-hydrogen bonds between the C4 and C5 hydrogen atoms.
In February 2014, NASA announced a greatly upgraded database for tracking polycyclic aromatic hydrocarbons (PAHs), including phenanthrene, in the universe. According to scientists, more than 20% of the carbon in the universe may be associated with PAHs, possible starting materials for the formation of life. PAHs seem to have begun forming a couple of billion years after the Big Bang, are widespread throughout the universe, and are associated with new stars and exoplanets.
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