Electrophilic aromatic directing groups (original) (raw)
En química, especialmente en química orgánica, se dice que un grupo funcional es un grupo activante o grupo activador cuando aumenta la reactividad química de la molécula hacia un tipo de reacción química particular. La expresión grupo activante suele aplicarse en química de compuestos aromáticos, en donde el grupo activante es un sustituyente del anillo que aumenta la reactividad del mismo en las reacciones de sustitución electrofílica aromática (SEAr).Los grupos activadores modifican la reactividad de un grupo funcional al alterar la densidad electrónica de este último. Este cambio en la densidad electrónica facilita reacciones posteriores.
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| dbo:abstract | In electrophilic aromatic substitution reactions, existing substituent groups on the aromatic ring influence the overall reaction rate or have a directing effect on positional isomer of the products that are formed. An electron donating group (EDG) or electron releasing group (ERG, Z in structural formulas) is an atom or functional group that donates some of its electron density into a conjugated π system via resonance (mesomerism) or inductive effects (or induction)—called +M or +I effects, respectively—thus making the π system more nucleophilic. As a result of these electronic effects, an aromatic ring to which such a group is attached is more likely to participate in electrophilic substitution reaction. EDGs are therefore often known as activating groups, though steric effects can interfere with the reaction. An electron withdrawing group (EWG) will have the opposite effect on the nucleophilicity of the ring. The EWG removes electron density from a π system, making it less reactive in this type of reaction, and therefore called deactivating groups. EDGs and EWGs also determine the positions (relative to themselves) on the aromatic ring where substitution reactions are most likely to take place; this property is therefore important in processes of organic synthesis. Electron donating groups are generally ortho/para directors for electrophilic aromatic substitutions, while electron withdrawing groups are generally meta directors with the exception of the halogens which are also ortho/para directors as they have lone pairs of electrons that are shared with the aromatic ring. (en) En química, especialmente en química orgánica, se dice que un grupo funcional es un grupo activante o grupo activador cuando aumenta la reactividad química de la molécula hacia un tipo de reacción química particular. La expresión grupo activante suele aplicarse en química de compuestos aromáticos, en donde el grupo activante es un sustituyente del anillo que aumenta la reactividad del mismo en las reacciones de sustitución electrofílica aromática (SEAr).Los grupos activadores modifican la reactividad de un grupo funcional al alterar la densidad electrónica de este último. Este cambio en la densidad electrónica facilita reacciones posteriores. (es) 配向性（はいこうせい）とは、ベンゼン環上の親電子置換反応において、置換基が及ぼす反応位置選択性を言い表す化学用語である。 (ja) 苯环的亲电取代定位效应（英語：Orientation effect of electrophilic aromatic directing groups）是指苯环上已有的取代基对亲电取代反应的影响。1895年（Holleman）等从大量实验事实中归纳出这一规律。主要有两种影响：一、活化苯环，有利于亲电取代反应的发生；二、钝化苯环，不利于亲电取代反应的发生。 (zh) |
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| rdfs:comment | En química, especialmente en química orgánica, se dice que un grupo funcional es un grupo activante o grupo activador cuando aumenta la reactividad química de la molécula hacia un tipo de reacción química particular. La expresión grupo activante suele aplicarse en química de compuestos aromáticos, en donde el grupo activante es un sustituyente del anillo que aumenta la reactividad del mismo en las reacciones de sustitución electrofílica aromática (SEAr).Los grupos activadores modifican la reactividad de un grupo funcional al alterar la densidad electrónica de este último. Este cambio en la densidad electrónica facilita reacciones posteriores. (es) 配向性（はいこうせい）とは、ベンゼン環上の親電子置換反応において、置換基が及ぼす反応位置選択性を言い表す化学用語である。 (ja) 苯环的亲电取代定位效应（英語：Orientation effect of electrophilic aromatic directing groups）是指苯环上已有的取代基对亲电取代反应的影响。1895年（Holleman）等从大量实验事实中归纳出这一规律。主要有两种影响：一、活化苯环，有利于亲电取代反应的发生；二、钝化苯环，不利于亲电取代反应的发生。 (zh) In electrophilic aromatic substitution reactions, existing substituent groups on the aromatic ring influence the overall reaction rate or have a directing effect on positional isomer of the products that are formed. An electron donating group (EDG) or electron releasing group (ERG, Z in structural formulas) is an atom or functional group that donates some of its electron density into a conjugated π system via resonance (mesomerism) or inductive effects (or induction)—called +M or +I effects, respectively—thus making the π system more nucleophilic. As a result of these electronic effects, an aromatic ring to which such a group is attached is more likely to participate in electrophilic substitution reaction. EDGs are therefore often known as activating groups, though steric effects can inter (en) |
| rdfs:label | Grupo activante (es) Electrophilic aromatic directing groups (en) 配向性 (ja) 苯环的亲电取代定位效应 (zh) |
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