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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.
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 ...
Here, a strong Lewis acid is required to generate either a carbocation from an alkyl halide in the Friedel-Crafts alkylation reaction or an acylium ion from an acyl halide. In the vast majority of cases, reactions that involve leaving group activation generate a cation in a separate step, before either nucleophilic attack or elimination.
A graph showing the relative reactivities of the different alkyl halides towards S N 1 and S N 2 reactions (also see Table 1). In 1935, Edward D. Hughes and Sir Christopher Ingold studied nucleophilic substitution reactions of alkyl halides and related compounds. They proposed that there were two main mechanisms at work, both of them competing ...
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 alkyl group migrates in the order of thermodynamical stability methyl < primary alkyl < secondary alkyl < tertiary alkyl, this is in line with the radical mechanism. The radical-ketyl pair is short lived and due to a solvent cage effect some isomerizations take place with retention of configuration .
The coupling of an acetylide and tertiary alkyl halide is an example of a reaction that cannot be accomplished with alkali metal acetylides, which displace halides in an S N 2 fashion. The corresponding alkynylalanes are able to couple to tertiary halides via an S N 1-like mechanism. [4] (11)
Steric effects of the alkyl substituents on the carbonyl reactant have been shown to affect both the rates and yields of Büchner–Curtius–Schlotterbeck reaction. Table 1 shows the percent yield of the ketone and epoxide products as well as the relative rates of reaction for the reactions between several methyl alkyl ketones and diazomethane ...