Ionic rearrangements

III. REARRANGEMENTS OF SULFOXIDES TO SULFENATES A. Thermal and Ionic Rearrangements... 

The mechanism was then formulated as an extension to the general theory of ionic rearrangements discussed by Zimmerman and Zweig 129). The proposed slow step in the reaction scheme is shown in (7)... 

The fact that only one proton exchanges therefore indicates that [23] is an edge protonated compound. The behaviour of the butyl system is typical of the pentyl system and hexyl system in all of which exchange studies indicate that edge-protonated cyclopropanes form during many ionic rearrangements in this acid (again with the assumption that a protonated cyclopropane is a bona fide intermediate) (Kramer, 1970). 

Kennerly and Patterson (13) studied the effect of several organic sulfur compounds, including thiols, sulfides, a disulfide, sulfonic acids, and a zinc dialkyl dithiophosphate, on the decomposition rate of cumene hydroperoxide in white mineral oil at 150 °C. In each case they found phenol as the major product. They suggested that the most attractive mechanism by which to explain these results involves ionic rearrangement catalyzed by acids or other electrophilic reagents (10) as... 

More recently, acetylene is reported to give under irradiation a photoadduct 48 with enone 47 by a-attack [46], After deacetoxylation and ionic rearrangement, a simple approach to the synthesis of optically active trichothecene seems possible [46 a] using the rearranged cyclopenteno bicyclic compound 48 (Scheme 22). 

Cationic polymerizations generally have no formal termination process. Dead chains are produced by what amounts to an ionic rearrangement of the propagating species, which produces an olefin-terminated chain and regenerates the first active catalyst species (Eq. 22.22). 

A chemical system which has reached a state of thermodynamic reversibility shows no further net reaction in either direction, since AG = 0. Such a system is said to be in a state of equilibrium, from which it could be displaced either forwards or backwards by an appropriate very small change in one of the variables. Although a system at equilibrium shows no net changes in the concentrations of any of the chemical species, the actual molecular or ionic rearrangements constituting both forward and reverse reactions may still be occurring, but the opposing forward and reverse reactions proceed at equal speeds. 

Isomerizations of allylic azides also appear to involve concerted, non-ionic rearrangements. Butenyl and pentenyl azides isomerize slowly at room temperature in a variety of solvents, viz. 

Fig. 3.1. Illustration of the ionic rearrangement in the a cubic to b tetragonal ferroelectric phase transition in BaTiOs...

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