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In meta-substitution, the substituents occupy positions 1 and 3 (corresponding to R and meta in the diagram). In para-substitution, the substituents occupy the opposite ends (positions 1 and 4, corresponding to R and para in the diagram). The toluidines serve as an example for these three types of substitution.
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 ...
Both the regioselectivity—the diverse arene substitution patterns—and the speed of an electrophilic aromatic substitution are affected by the substituents already attached to the benzene ring. In terms of regioselectivity, some groups promote substitution at the ortho or para positions, whereas other groups favor substitution at the meta ...
Halogen substituents are an exception: they are resonance donors (+M). With the exception of the halides, they are meta directing groups. Halides are ortho, para directing groups but unlike most ortho, para directors, halides mildly deactivate the arene. This unusual behavior can be explained by two properties:
In organic chemistry, aromatic sulfonation is an reaction in which a hydrogen atom on an arene is replaced by a sulfonic acid (−SO 2 OH) group. Together with nitration and chlorination, aromatic sulfonation is a widely used electrophilic aromatic substitutions. [1] Aryl sulfonic acids are used as detergents, dye, and drugs.
The Gatterman reaction describes arene reactions with hydrocyanic acid. [19] [20] The Houben–Hoesch reaction describes arene reactions with nitriles. [21] A reaction modification with an aromatic phenyl ester as a reactant is called the Fries rearrangement. In the Scholl reaction two arenes couple directly (sometimes called Friedel–Crafts ...
The metal–arene product can also add to another aryne, leading to chain-growth polymerization. Using copper(I) cyanide as the initiator to add to the first aryne yielded polymers containing up to about 100 arene units. [22] When leaving group (LG) and substituent (Y) are mutually ortho or para, only one benzyne intermediate is possible.
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