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Two resonance structures of phenanthrene: above, one with only one circle; below, one with two circles, which is also a Clar's structure. Clar's rule states that the latter structure contributes the most to the properties of phenanthrene.
Phenanthrene is a polycyclic aromatic hydrocarbon (PAH) with formula C 14 H 10, consisting of three fused benzene rings. It is a colorless, crystal-like solid, but can also appear yellow. It is a colorless, crystal-like solid, but can also appear yellow.
Pyrene is a polycyclic aromatic hydrocarbon (PAH) consisting of four fused benzene rings, resulting in a flat aromatic system. The chemical formula is C 16 H 10.This yellow-green solid is the smallest peri-fused PAH (one where the rings are fused through more than one face).
According to one, the relative stability of phenanthrene compared to its isomers can be adequately explained by comparing resonance stabilizations. [8] Another critic argues that the stability of phenanthrene can be attributed to more effective pi-pi overlap in the central double bond; the existence of bond paths is not questioned but the ...
ortho-Substituted substrates generally give 1-substituted phenanthrenes, unless the substituent is a good leaving group, in which case elimination to form unsubstituted phenanthrene occurs. [11] meta- Substituted substrates give mixtures of 2- and 4-substituted products. Substitution of the exocyclic double bond is well tolerated.
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Also, there are no carbocation rearrangements, as the acylium ion is stabilized by a resonance structure in which the positive charge is on the oxygen. The viability of the Friedel–Crafts acylation depends on the stability of the acyl chloride reagent. Formyl chloride, for example, is too unstable to be isolated.
Triphenylene is more resonance stable than its isomers chrysene, benzanthracene, benzophenanthrene, and tetracene. For this reason triphenylene resists hydrogenation. [5] As a disc-shaped, planar molecule, triphenylene has attracted attention as the core of discotic mesogen in liquid crystalline materials. [6]