Polar effect

Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [1] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.

The Polar effect or electronic effect in chemistry is the effect exerted by a substituent on modifying electrostatic forces operating on a nearby reaction center. The main contributors to the polar effect are the inductive effect, mesomeric effect and the through-space electronic field effect.

An electron withdrawing group or EWG draws electrons away from a reaction center. When this center is an electron rich carbanion or an alkoxide anion the presence of the substituent has a stabilizing effect.

Examples of electron withdrawing groups are:

• halogens (F, Cl),
• nitriles CN,
• carboxylic acids COOH
• carbonyls CO

An electron releasing group or ERG (otherwise called electron donating groups or EDG) releases electrons into a reaction center and as such stabilizes electron deficient carbocations.

Examples of electron releasing groups are:

• alkyl groups
• alcohol groups
• amino groups

The total substituent effect is the combination of the polar effect and the combined steric effects.

In electrophilic aromatic substitution and nucleophilic aromatic substitution substituents are divided into activating groups and deactivating groups where the direction of activation or deactivation is also taken into account.

• Polar effect definition by the IUPAC Gold Book Link

Template:SIB