Electrophilic Addition Reaction

An addition reaction is an organic reaction where two or more molecules combine to form a larger molecule as the only product. The electrophilic addition reaction is the most common reaction of C-C multiple bonds. The C-C double bond is a region of high electron density making it nucleophilic in nature which can make it susceptible to attack from electrophiles. Electrophilic addition reactions are typical of unsaturated organic compounds e.g. alkenes (which contain a C-C double bond) or alkynes (which contain a C-C triple bond).

Figure 1. General addition reaction scheme

The reaction is driven by the conversion of the weaker pi bond (C=C) into two new stronger sigma bonds. Conceptually, addition is the reverse of elimination which can be used to prepare alkenes.

A wide variety of reagents can undergo addition reactions to provide a diversity of chemical products. There are 3 factors that could potentially influence the outcome of an addition reaction:

  1. Overall functional group conversion (e.g. C=C to new functional group)

  2. Regioselectivity - if the two atoms that add to C=C are different

  3. Stereochemistry - if the two atoms that add to C=C are different