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The Buchner ring expansion reaction was first used in 1885 by Eduard Buchner and Theodor Curtius [1] [2] who prepared a carbene from ethyl diazoacetate for addition to benzene using both thermal and photochemical pathways in the synthesis of cycloheptatriene derivatives. The resulting product was a mixture of four isomeric carboxylic acids ...
The use of the prefixes ortho, meta and para to distinguish isomers of disubstituted aromatic rings starts with Wilhelm Körner in 1867, although he applied the ortho prefix to a 1,4-isomer and the meta prefix to a 1,2-isomer. [6] [7] It was the German chemist Karl Gräbe who, in 1869, first used the prefixes ortho-, meta-, para- to denote ...
[1] [2] Simple aromatic rings can be heterocyclic if they contain non-carbon ring atoms, for example, oxygen, nitrogen, or sulfur. They can be monocyclic as in benzene, bicyclic as in naphthalene, or polycyclic as in anthracene. Simple monocyclic aromatic rings are usually five-membered rings like pyrrole or six-membered rings like pyridine.
Heteroarenes are aromatic compounds, where at least one methine or vinylene (-C= or -CH=CH-) group is replaced by a heteroatom: oxygen, nitrogen, or sulfur. [3] Examples of non-benzene compounds with aromatic properties are furan, a heterocyclic compound with a five-membered ring that includes a single oxygen atom, and pyridine, a heterocyclic compound with a six-membered ring containing one ...
Ring expansions can allow access to larger systems that can be difficult to synthesize otherwise. [6] Rings can be expanded by attack of the ring onto an outside group already appended to the ring (a migration/insertion), opening of a bicycle to a single larger ring, or coupling a ring closing with an expansion. [1]
Hexacene is an aromatic compound consisting of six linearly-fused benzene rings. It is a blue-green, air-stable solid with low solubility. [1]Hexacene is one of a series of linear polycyclic molecules created by such aromatic ring fusions, a series termed acenes; the previous in the series is pentacene (with five fused rings) and the next is heptacene (with seven).
Benzene and cyclohexane have a similar structure, only the ring of delocalized electrons and the loss of one hydrogen per carbon distinguishes it from cyclohexane. The molecule is planar. [ 58 ] The molecular orbital description involves the formation of three delocalized π orbitals spanning all six carbon atoms, while the valence bond ...
Structure and AFM image of dehydrobenzo[12]annulene, where benzene rings are held together by triple bonds. A triple bond in chemistry is a chemical bond between two atoms involving six bonding electrons instead of the usual two in a covalent single bond. Triple bonds are stronger than the equivalent single bonds or double bonds, with a bond ...