Preferred Label : umpolung;
IUPAC definition : Any process by which the normal alternating donor and acceptor reactivity pattern
of a chain, which is due to the presence of O or N heteroatoms, is interchanged. Reactivity
umpolung is most often achieved by temporary exchange of heteroatoms (N, O) by others,
such as P, S and Se. The original meaning of the term has been extended to the reversal
of any commonly accepted reactivity pattern. For example, reaction of R–C CX (X
halide) as a synthon for 'R–C C sup class plus /sup (i.e. electrophilic acetylene)
is an umpolung of the normal more common acetylide, R–C C sup class minus /sup
(i.e. nucleophilic) reactivity.;
Origin ID : U06551;
See also
Any process by which the normal alternating donor and acceptor reactivity pattern
of a chain, which is due to the presence of O or N heteroatoms, is interchanged. Reactivity
umpolung is most often achieved by temporary exchange of heteroatoms (N, O) by others,
such as P, S and Se. The original meaning of the term has been extended to the reversal
of any commonly accepted reactivity pattern. For example, reaction of R–C CX (X
halide) as a synthon for 'R–C C sup class plus /sup (i.e. electrophilic acetylene)
is an umpolung of the normal more common acetylide, R–C C sup class minus /sup
(i.e. nucleophilic) reactivity.
