| Aromatic Ortho Substituent |
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Information AboutAromatic Ortho Substituent |
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In ortho-substitution, two substituents share positions next to each other and in '''meta-substitution''' the substituents occupy positions 1 and 3. In '''para-substitution''', the substituents occupy the opposite ends (positions 1 and 4). The Toluidine s serve as an example for this type of substitution. In special cases, ipso-substitution describes two substituents sharing the same ring position in an intermediate compound in an Electrophilic Aromatic Substitution . '''Meso-substitution''' is observed in compounds such as Calixarene s and Acridine s and refer to the substituents occupying a Benzyl ic position. In Naphthalene s, substitution specifically in the 1 and 8 positions is called peri-substitution. ORIGINS The meanings of the prefixes ''ortho'', ''meta'' and ''para'' are all derived from Greek: respectively meaning ''straight or correct'', ''following or after'' or ''akin to or similar'' and 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, see for instance the trivial names ) 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 . REFERENCES |
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