Rearrangements pseudorotations

One type of permutational rearrangement, known as pseudorotation, can be visualized as in Eq. 12-28.668 669 The axial groups a and b move back while equatorial groups 2 and 3 move forward, still in the same equato-... 

There are perhaps only two research areas in which the quantitative estimation of steric factors is routinely done, namely for hindered biphenyls (Cooke and Harris, 1967) and rotational or pseudorotation barriers in ethanes and cyclic compounds (Allinger et al., 1967). There are indications, however, that this interest is widening. Simonetta and Favini (1966) performed conformational calculations on the Cope rearrangement via chair or boat transition states and indicated that the orbital preference emphasized in a previous section should be supplemented with a steric factor. 

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

Permutational isomerization of pentavalent phosphorus compounds, 9, 25 Phosphorous compounds, pentavalent, turnstile rearrangement and pseudorotation in permutational isomerization, 9, 26 Planar and non-planar aromatic systems, 1, 203 Polarizability, molecular refractivity and, 3,1 Polarography and reaotion kinetios, 5, 1 Polypeptides, calculations of conformations of, 6, 103... 

Iodine heptafluoride, IF7, has a pentagonal bipyramidal structure of at least approximately D5h symmetry [118], Its dynamic behavior has been desribed by pseudorotation. The rearrangement that characterizes the PF5 molecule also describes well the permutation of... 

The pseudorotation phenomenon is vital to structural chemistry of phosphorus, silicon, transitional metals, and some other elements. Apart from pseudorotation, there are other rearrangement mechanisms, for example, trigonal twist (Fig. 48a) examined in dynamic stereochemistry of icosahedral carboranes, tourniquet mechanism (Fig. 486), etc. 

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