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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 ...
Structures and names of common heterocyclic compounds Pyridine, a heterocyclic compound. A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). [1]
Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline.
Typical simple aromatic compounds are benzene, indole, and pyridine. [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.
The model for benzene consists of two resonance forms, which corresponds to the double and single bonds superimposing to produce six one-and-a-half bonds. Benzene is a more stable molecule than would be expected without accounting for charge delocalization. [citation needed]
A C=C bond is shorter than a C−C bond, but benzene is perfectly hexagonal—all six carbon-carbon bonds have the same length, intermediate between that of a single and that of a double bond. A better representation is that of the circular π bond (Armstrong's inner cycle ), in which the electron density is evenly distributed through a π-bond ...
According to the rules expressed above, the phenanthrene molecule allows two different resonance structures: one of them presents a single circle in the center of the molecule, with each of the two adjacent rings having two double bonds; the other one has the two peripheral rings each with one circle, and the central ring with one double bond.
The generated carbene adds to one of the double bonds of benzene to form the cyclopropane ring. carbene insertion. The advent of transition metal catalyzed reagents provides alternative stereospecific methods for cyclopropanation. The choices for metals include Cu, Rh and Ru with a variety of ligands. [13]