Term
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Definition
strongly activating
ortho/para directing
electron donating group |
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Term
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Definition
strongly activating
ortho/para directing
electron donating group |
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Term
|
Definition
strongly activating
ortho/para directing
electron donating group |
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Term
|
Definition
strongly activating
ortho/para directing
electron donating group |
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Term
|
Definition
strongly activating
ortho/para directing
electron donating group |
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Term
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Definition
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Term
|
Definition
moderately activating
ortho/para directing
electron donating group |
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Term
|
Definition
moderately activating
ortho/para directing
electron donating group |
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Term
|
Definition
weakly activating
ortho/para directing
electron donating group |
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Term
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Definition
weakly activating
ortho/para directing
electron donating group |
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Term
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Definition
weakly activating
ortho/para directing
electron donating group |
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Term
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Definition
weakly activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
moderately activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
moderately activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
moderately activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
moderately activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
moderately activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
strongly activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
strongly activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
strongly activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
strongly activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
strongly activating
meta directing
electron withdrawing groups
deactivating |
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Term
|
Definition
strongly activating
meta directing
electron withdrawing groups
deactivating |
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Term
| Electron withdrawing groups (EWG) |
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Definition
with p bonds to electronegative atoms (e.g. -C=O, -NO2) adjacent to the p system deactivate the aromatic ring by decreasing the electron density on the ring through a resonance withdrawing effect. The resonance only decreases the electron density at the ortho- and para- positions. Hence these sites are less nucleophilic, and so the system tends to react with electrophiles at the meta sites.Halogen substituents are a little unusual in that they are deactivating but still direct ortho- / para-. The reason is that they are both inductive electron withdrawing (electronegativity) and resonance donating (lone pair donation). The inductive effect lowers the reactivity but the resonance effect controls the regiochemistry due to the stability of the intermediates.
Besides the electronic effects, substitutents can also influence product distributions due to steric effects.
The regioselectivity for further substitution of disubstituted benzenes can usually be predicted by looking at the cumulative effects of the substituents. |
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Term
| Electron donating groups (EDG) |
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Definition
| with lone pairs (e.g. -OMe, -NH2) on the atoms adjacent to the p system activate the aromatic ring by increasing the electron density on the ring through a resonance donating effect. The resonance only allows electron density to be positioned at the ortho- and para- positions. Hence these sites are more nucleophilic, and the system tends to react with electrophiles at these ortho- and para- sites. |
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