Ortho Para Directors
Ortho Para Directors - Related Videos
08:43
Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives
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2016
An operationally simple procedure for the synthesis of ortho-trifluoromethoxylated aniline derivatives via a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxyacetamide followed by thermally induced intramolecular OCF3-migration is reported.
01:14
Directing Effect of Substituents: ortho–para-Directing Groups
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2025
Ortho–para directors are substituent groups attached to the benzene ring and direct the addition of an electrophile to the positions ortho or para to the substituent. All electron-donating groups are considered ortho–para directors. They donate electrons to the ring and make the ring more electron-rich. The ring is therefore susceptible to the addition of electrophiles. Substituents such as amino, hydroxy, or alkoxy, containing lone pairs on the atom adjacent to the ring, donate electrons...
01:24
ortho–para-Directing Deactivators: Halogens
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2023
Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...
01:11
ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
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2025
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
03:35
Rapid Quantification of Oxidized and Reduced Forms of Glutathione Using Ortho -phthalaldehyde in Cultured Mammalian Cells In Vitro
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Cited by 2 •
2024
Quantification of both oxidized and reduced forms of glutathione (GSSG and GSH, respectively) has been achieved through the use of Ortho-phthalaldehyde (OPA). OPA becomes highly fluorescent once conjugated to GSH but is unable to conjugate GSSG until reduced. Here, we describe a multiparametric assay to quantify both using protein quantification for normalization.
FAQs
The arenium ion, or sigma complex, is the key intermediate formed after an electrophile attacks an aromatic ring. Its stability differs according to the site of attack because the substituent can influence the intermediate through resonance and inductive effects. Comparing these stabilized intermediates helps explain why one substitution pattern is favored over another.
Resonance donation from a substituent can stabilize the sigma complex formed when attack occurs at positions related to that group. This stabilization lowers the relative disadvantage of those intermediates and supports formation of ortho or para products. The effect is especially important for electron-donating substituents, which generally activate the aromatic ring toward electrophilic substitution.
Halogens illustrate that directing influence and overall reactivity are separate properties. Their inductive withdrawal deactivates the aromatic ring, making electrophilic substitution less favorable overall. At the same time, resonance donation can stabilize sigma complexes associated with ortho and para attack, so halogen-substituted rings retain that directing preference despite their reduced activation.
A substituent can affect both how readily the ring reacts and where substitution occurs, but these outcomes are not identical. Most electron-donating groups activate the ring and favor ortho or para attack, whereas halogens deactivate while maintaining the same positional preference. Separating reactivity from regiochemical direction prevents contradictory predictions.
First identify the substituent already attached to the aromatic ring, then determine whether its electronic behavior favors ortho and para attack. Next, use that preference to predict where the incoming electrophile is most likely to form a new bond. This approach provides a regiochemical expectation before interpreting the reaction product.
In multistep synthesis, directing effects help anticipate how each existing substituent will influence a later electrophilic substitution. Planning therefore requires considering both the position already occupied and the electronic character of the substituent controlling the next reaction. This analysis helps organize a sequence toward the desired substitution pattern rather than treating each step independently.
An observed substitution pattern can indicate which sigma-complex pathway received greater stabilization during electrophilic attack. Predominant ortho or para products support the influence of resonance donation by the existing substituent, while reduced overall reaction tendency may reflect inductive withdrawal. Product distributions therefore connect experimental outcomes with electronic effects in the aromatic intermediate.