In biochemistry, a consecutive series of chemical reactions form metabolic pathways. Enzymes increase the rates of biochemical reactions, so that metabolic syntheses and decompositions impossible under ordinary conditions can occur at the temperatures and concentrations present within a cell. The other types of substitution reactions include radical reactions and organometallic substitution reaction.

Hence, that face of the carbocation is shielded by the anion, so the carbocation is captured preferentially by a nucleophile that attacks from the opposite face. The experimental result is formation of a net excess of the product with inversion of configuration. Therefore, they are less reactive towards nucleophilic substitution reaction. In compound and compound , halogen atom is directly bonded to aromatic ring therefore these compounds are classified as aryl halides. Both reactions and are known to be exothermic, nevertheless possible potential energy barriers along the reaction path may hinder one or both channels.

Furthermore, the carbon atom bearing the nucleophile and the leaving group is pentacoordinate in the transition state. As a consequence, there is more crowding in the transition state. The energy barrier for the formation of the transition state increases with the size of the groups bonded to the reactive center, so steric effects are very important.

Like arene oxides, epoxides formed from alkenes also react with glutathione to produce water-soluble compounds that are easily eliminated from the body. Epoxides derived from alkenes also undergo ring-opening reactions with macromolecules. Thus, the Grignard reagent of bromoethane behaves as an ethyl do fungi have chloroplasts carbanion. Nucleophilic attack of the ethyl carbanion on 2-methyloxirane occurs at the primary rather than the secondary carbon atom. Subsequent hydrolysis of the magnesium alkoxide yields 2-pentanol. The nucleophile attacks the less hindered primary carbon atom instead of the tertiary carbon atom.

Meisenheimer intermediates can be isolated and characterized. However, if heated, the compound goes on to form the final nucleophilic aromatic substitution product. Well, for one thing, this would suggest that, unlike the SN1 and SN2 reactions, C-F bond cleavage does not occur in the rate-determining step.