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Electron-withdrawing groups exert an "inductive" or "electron-pulling" effect on covalent bonds. The strength of the electron-withdrawing group is inversely proportional to the pKa of the carboxylic acid. [2] The inductive effect is cumulative: trichloroacetic acid is 1000x stronger than chloroacetic acid.
The captodative effect is the stabilization of radicals by a synergistic effect of an electron-withdrawing substituent and an electron-donating substituent. [2] [3] The name originates as the electron-withdrawing group (EWG) is sometimes called the "captor" group, whilst the electron-donating group (EDG) is the "dative" substituent. [3]
The effect is used in a qualitative way and describes the electron withdrawing or releasing properties of substituents based on relevant resonance structures and is symbolized by the letter M. [2] The mesomeric effect is negative ( –M ) when the substituent is an electron-withdrawing group , and the effect is positive ( +M ) when the ...
A bicycloheptane acid with an electron-withdrawing substituent, X, at the 4-position experiences a field effect on the acidic proton from the C-X bond dipole. [4] A bicyclooctance acid with an electron-witituent, X, at the 4-position experiences the same field effect on the acidic proton from the C-X bondole as the related bicylcoheptane.
If the electronegative atom (missing an electron, thus having a positive charge) is then joined to a chain of atoms, typically carbon, the positive charge is relayed to the other atoms in the chain. This is the electron-withdrawing inductive effect, also known as the -I effect. In short, alkyl groups tend to donate electrons, leading to the +I ...
The sulfonyl functional group (RS(O) 2 R') has become an important electron-withdrawing group for modern organic chemistry. α-Sulfonyl carbanions may be used as nucleophiles in alkylation reactions, Michael-type additions, and other processes. [3] After having served their synthetic purpose, sulfonyl groups are often removed.
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The substituent R next the amine methylene bridge is an electron-withdrawing group. The original 1928 publication by Thomas S. Stevens [2] concerned the reaction of 1-phenyl-2-(N,N-dimethylamino)ethanone with benzyl bromide to the ammonium salt followed by the rearrangement reaction with sodium hydroxide in water to the rearranged amine.