Are you an EPFL student looking for a semester project?
Work with us on data science and visualisation projects, and deploy your project as an app on top of Graph Search.
Concept
Arene substitution pattern
Summary
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.
Electrophilic aromatic substitution
In ortho-substitution, two substituents occupy positions next to each other, which may be numbered 1 and 2. In the diagram, these positions are marked R and ortho.
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.
Electron donating groups, for example amino, hydroxyl, alkyl, and phenyl groups tend to be ortho/para-directors, and electron withdrawing groups such as nitro, nitrile, and ketone groups, tend to be meta-directors.
Although the specifics vary depending on the compound, in simple disubstituted arenes, the three isomers tend to have rather similar boiling points. However, the para isomer usually has the highest melting point, and the lowest solubility in a given solvent, of the three isomers.
Because electron donating groups are both ortho and para directors, separation of these isomers is a common problem in synthetic chemistry. Several methods exist in order to separate these isomers:
Column chromatography will often separate these isomers, as the ortho is more polar than the para in general.
Fractional crystallisation can be used to obtain pure para product, relying on the principle that it is less soluble than the ortho and thus will crystallise first. Care must be taken to avoid cocrystallisation of the ortho isomer.
Many nitro compounds' ortho and para isomers have quite different boiling points. These isomers can often be separated by distillation. These separated isomers can be converted to diazonium salts and used to prepare other pure ortho or para compounds.
Image:Ipso Substitution V.3.svg|''ipso''- substitution.
Official source
About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.