Permutational isomerism

Partitioning of carbocations between addition of nucleophiles and deprotonation, 35, 67 Perchloro-organic chemistry structure, spectroscopy and reaction pathways, 25, 267 Permutational isomerization of pentavalent phosphorus compounds, 9, 25 Phase-transfer catalysis by quaternary ammonium salts, 15, 267 Phosphate esters, mechanism and catalysis of nucleophilic substitution in, 25, 99 Phosphorus compounds, pentavalent, turnstile rearrangement and pseudoration in permutational isomerization, 9, 25... 

It is a particular advantage of the permutation descriptors that they do not only represent configurations, but provide also a basis for the representation of configuration interconversions. The permutational isomerization (PI) of a configuration A into a configuration B is described by the isomerizer Iab = Pb Pa 1, with Pa and Pb being the permutation descriptors of A and B. 

Tetracoordinate sulfur compounds containing a lone pair of electrons at sulfur possess a more or less distorted trigonal-bipyramidal structure, in common with the vast majority of other pentacoordinated molecules of the main group elements (189,191,199). A common name, sulfurane, is generally accepted for this type of compound. In principle, sulfuranes are chiral. However, both the number of optically active isomers and their optical stability depend on the nature of substituents bonded to the central sulfur atom, the apicophilicity of the substituents, and the energy required for permutational isomerization processes. In this context it is interesting to note that acyclic sulfuranes with four different ligands should exist in 20 isomeric forms. 

TURNSTILE REARRANGEMENT AND PSEUDOROTATION IN THE PERMUTATIONAL ISOMERIZATION OF PENTAVALENT PHOSPHORUS... 

IX. Irregular Permutational Isomerizations of Compounds with Pentavalent... 

Permutational isomerization, i.e., the interconversion of permutational isomers, is the redistribution of ligands on any polytopal framework. This redistribution can take place by two different processes ... 

The regular permutational isomerizations (or regular polytopal rearrangements) take place without the rupture of bonds, i.e., with preservation of neighborhood relationships. 

The irregular permutational isomerizations (or irregular polytopal rearrangements) occur with fission and re-formation of bonds. 

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