Nucleophilic addition is an addition reaction where in a chemical compound a π bond is removed by the creation of two new covalent bonds by the addition of a nucleophile.
Addition reactions are limited to chemical compounds that have multiple-bonded atoms such as:
- Molecules with carbon double bonds such as Alkenes
- Molecules with carbon triple bonds such as Alkynes
Nucleophilic addition in molecules with carbon-hetero double bonds
Above is an example of a 1,2 nucleophilic addition. The C=O bond is polar (there is a large difference in in electronegativity between the carbon and oxygen) and consequently carbon carries a small positive charge. This makes the carbon atom the primary target for the nucleophile (noted as Nu in the diagram).
Steric factors to be taken into account
- Alkyl groups are bigger than hydrogen
- Ketone carbonyls are less susceptible to nucleophiles.
- Tetrahedral products are more crowded than planar aldehydes or ketones.
- The product from a ketone is more crowded than that from an aldehyde.