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The mechanism of S N 2 reaction does not occur due to steric hindrance of the benzene ring. In order to attack the C atom, the nucleophile must approach in line with the C-LG (leaving group) bond from the back, where the benzene ring lies. It follows the general rule for which S N 2 reactions occur only at a tetrahedral carbon atom.
Diagram showing the ortho, meta and para positions relative to a substituent X on a benzene ring. Electron donating groups are typically divided into three levels of activating ability (The "extreme" category can be seen as "strong".) Electron withdrawing groups are assigned to similar groupings.
Benzonitrile is the chemical compound with the formula C 6 H 5 (CN), abbreviated PhCN. This aromatic organic compound is a colorless liquid with a sweet bitter almond odour. It is mainly used as a precursor to the resin benzoguanamine .
Many simple aromatic rings have trivial names. They are usually found as substructures of more complex molecules ("substituted aromatics"). 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.
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 ...
An alkyne trimerisation is a [2+2+2] cycloaddition reaction in which three alkyne units (C≡C) react to form a benzene ring. The reaction requires a metal catalyst. The process is of historic interest as well as being applicable to organic synthesis. [1] Being a cycloaddition reaction, it has high atom economy.
The Nencki reaction (1881) is the ring acetylation of phenols with acids in the presence of zinc chloride. [24] In a green chemistry variation aluminium chloride is replaced by graphite in an alkylation of p-xylene with 2-bromobutane. This variation will not work with primary halides from which less carbocation involvement is inferred. [25]
As it generally begins with nucleophilic attack by the aromatic group, the electron density of the ring is an important factor. Some aromatic compounds, such as pyrrole, are known to formylate regioselectively. [6] Formylation of benzene rings can be achieved via the Gattermann reaction and Gattermann-Koch reaction.