Sulfur atom exchange

PROTONS ON OXYGEN, NITROGEN, AND SULFUR ATOMS. EXCHANGEABLE PROTONS... 

Another possible source of chemical MIF is self-reaction of the SO radical, which either yields S and SO2 as disproportionation products [41], or the SO dimer as an association product [42]. Two of the four lowesf energy singlef sfafes of the SO dimer [43] have a reduced point group symmetry upon sulfur isotope substitution. If sulfur atom exchange is another possible outcome in the self reaction of SO, then a symmetry-derived mass-independent effect analogous to O3 formation may be possible. A similar conclusion may be drawn for the triplet states of the SO dimer. 

The mobility of the proton in position 2 of a quaternized molecule and the kinetics of exchange with deuterium has been studied extensively (18-20) it is increased in a basic medium (21-23). The rate of exchange is close to that obtained with the base itself, and the protonated form is supposed to be the active intermediate (236, 664). The remarkable lability of 2-H has been ascribed to a number of factors, including a possible stabilizing resonance effect with contributions of both carbene and ylid structure. This latter may result from the interaction of a d orbital at the sulfur atom with the cr orbital out of the ring at C-2 (21). 

Structure. The thiosulfate sulfur atoms have been shown to be nonequivalent by radioactive sulfur exchange studies (1). When a sulfite is treated with radioactive sulfur and the resulting thiosulfate decomposed to sulfur and sulfite by acids, the radioactivity appears in the sulfur ... 

The rearrangement (automerization) of Dewar thiophene 5-oxide (61), observed by NMR, occurs so much more rapidly than that of the corresponding episulfide that special mechanisms have been invoked. The one which involves a zwitterionic intermediate (Scheme 108) is favored over a pseudopericyclic sulfur-walk mechanism in which the electrons of the carbon-sulfur o--bond and the pair of electrons on sulfur exchange places as the sulfur atom migrates around the ring (80JA2861). 

Chemical properties of disulfide dications are almost similar to the properties of disulfonium dications. Nucleophilic exchange is characteristic transformation of disulfide dications. Substitution occurs at sulfur atom with cleavage of disulfide moieties because of the lower energy of S-S bonds (Scheme 59). 

This indirect proof of the appearance of CF3SF leads to the conclusion that fluorination of sulfenyl chlorides of the series CF Cl3 SCl (n = 0, 1, 2) with alkali metal fluorides follows the mechanism observed in the formation of sulfenyl fluorides the initial chlorine-fluorine exchange at the sulfur atom is followed by isomerization to the sulfenyl chloride containing the corresponding more highly fluorinated methyl group. 

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