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Arene substitution patterns
Arene substitution patterns are part of organic chemistry IUPAC nomenclature and pinpoint the position of substituents other than hydrogen in relation to each other on an aromatic hydrocarbon.
Additional recommended knowledge
Ortho, meta, and para substitution
Ipso, meso, and peri substitution
Cine and tele substitution
The meanings of the prefixes ortho, meta and para are all derived from Greek: respectively meaning straight or correct, following or after and akin to or similar. The relationship to the current meaning is perhaps not obvious. The ortho description was historically used to designate the original compound and an isomer was often called the meta compound. For instance, the trivial names orthophosphoric acid and trimetaphosphoric acid have nothing to do with aromatics at all. Likewise the description para was reserved for just closely related compounds. Thus Berzelius originally called the racemic form of aspartic acid paraaspartic acid (another obsolete term: racemic acid) in 1830. The use of the descriptions ortho, meta and para for multiple substituted aromatic rings starts with Wilhelm Körner in the period 1866–1874 although he chose to reserve the ortho prefix for the 1,4 isomer and the meta prefix for the 1,2-isomer. The current nomenclature (different again from that of Körner) was introduced by the Chemical Society in 1879 .
Examples of the use of this nomenclature are given for isomers of cresol:
Catechol, resorcinol and hydroquinone are isomers also:
Phthalic acid has two isomers, the meta isomer isophthalic acid and the para isomer terephthalic acid:
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Arene_substitution_patterns". A list of authors is available in Wikipedia.|