Ortho Position
Ortho Position - 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...
02:32
Position-effect Variegation
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2020
In 1928, a German botanist Emil Heitz observed the moss nuclei with a DNA binding dye. He observed that while some chromatin regions decondense and spread out in the interphase nucleus, others do not. He termed them euchromatin and heterochromatin, respectively. He proposed that the heterochromatin regions reflect a functionally inactive state of the genome. It was later confirmed that heterochromatin is transcriptionally repressed, and euchromatin is transcriptionally active chromatin.
01:03
Serial Position Effect
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2025
The serial position effect is a cognitive phenomenon where individuals are more likely to recall the first and last items in a list compared to those in the middle. This effect is divided into the primacy effect and the recency effect. The primacy effect is observed when the initial items in a list are remembered better. This occurs because these items are rehearsed more frequently or receive more elaborative processing, allowing them to be encoded into long-term memory more effectively. For...
FAQs
Substituents modify electron density across an aromatic ring, so they can make adjacent positions more or less favorable for electrophilic attack. This electronic effect contributes to regioselectivity, the preference for reaction at particular ring locations. Evaluating the substituent’s influence helps explain why an electrophilic aromatic substitution reaction can produce one positional isomer more readily than another.
Steric interactions near the reference substituent can make formation of an adjacent substituted structure less favorable, even when electronic effects support attack at that location. As a result, the reaction may distribute material among products rather than strongly favoring the electronically preferred pathway. Considering steric crowding is therefore essential when explaining observed regioselectivity and product ratios.
Electronic effects indicate how favorable attack may be at a ring location, whereas steric effects reflect the spatial crowding created by nearby groups. These influences can point in the same direction or compete, so the most plausible ortho outcome requires considering both. This combined assessment provides a more reliable explanation of product distribution than either factor alone.
Begin by examining how the existing substituent changes electron density and then consider whether nearby groups create steric interactions at the prospective site. Comparing these influences helps identify which positional outcome is favored and whether competing products are likely. This approach connects the structural assignment of an ortho product with the reaction’s expected regioselectivity.
Assigning the substitution pattern of each proposed aromatic product allows chemists to determine whether reaction occurred at an ortho site and to compare that outcome with other possible positional products. The observed mixture can then be discussed in terms of electron-density effects and steric interactions, providing a structure-based explanation for the product distribution.
Correctly identifying this substitution pattern supports planning and evaluating syntheses of pharmaceuticals, dyes, and functional aromatic materials. In each case, the location of substituents affects how a structure is described and how reaction outcomes are interpreted. Linking the assigned position to regioselectivity helps researchers assess whether a product structure matches the intended aromatic design.