ABSTRACT
Displacement reactions at heteroatoms feature widely in both organic and bio-organic chemistry and they are among the most important processes in metabolism. This chapter talks about the transfer of electrophiles between nucleophiles but also includes hydrogen transferring formally with its valency electrons between electrophilic donors and acceptors; hydrogen transferring as an electrophile without its valency electrons. Despite its possessing a lone pair of electrons, nitrogen, in its trivalent level of oxidation can act as an electrophile. Positional isotopic exchange is a good diagnostic tool for the demonstration of a metaphosphate ion intermediate and has been employed extensively. Sulphyl group transfer at the divalent oxidation level is most important in biological systems and involves methyl group transfers and acyl transfer reactions. Sulphur transfer at the divalent level of oxidation is involved in disulphide cross-linking interchange processes which control the expression of newly formed protein.
